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Network Working Group
Request for Comments: 3867
Category: Informational
Y. Kawatsura
Hitachi
M. Hiroya
Technoinfo Service
H. Beykirch
Atos Origin
November 2004

Payment Application Programmers Interface (API) for v1.0
  Internet Open Trading Protocol (IOTP)

Status of this Memo

This memo provides information for the Internet community. It does not specify an Internet standard of any kind. Distribution of this memo is unlimited.

Copyright Notice

Copyright © The Internet Society (2004).

Abstract

The Internet Open Trading Protocol (IOTP) provides a data exchange format for trading purposes while integrating existing pure payment protocols seamlessly. This motivates the multiple layered system architecture which consists of at least some generic IOTP application core and multiple specific payment modules.

This document addresses a common interface between the IOTP application core and the payment modules, enabling the interoperability between these kinds of modules. Furthermore, such an interface provides the foundations for a plug-in-mechanism in actual implementations of IOTP application cores.

Such interfaces exist at the Consumers', the Merchants' and the Payment Handlers' installations connecting the IOTP application core and the payment software components/legacy systems.

Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
       1.1.  General payment phases . . . . . . . . . . . . . . . . .  5
       1.2.  Assumptions. . . . . . . . . . . . . . . . . . . . . . .  6
   2.  Message Flow . . . . . . . . . . . . . . . . . . . . . . . . . 12
       2.1.  Authentication Documentation Exchange. . . . . . . . . . 15
       2.2.  Brand Compilation. . . . . . . . . . . . . . . . . . . . 17
       2.3.  Brand Selection. . . . . . . . . . . . . . . . . . . . . 21
       2.4.  Successful Payment . . . . . . . . . . . . . . . . . . . 24
       2.5.  Payment Inquiry. . . . . . . . . . . . . . . . . . . . . 29
       2.6.  Abnormal Transaction Processing. . . . . . . . . . . . . 30
             2.6.1.  Failures and Cancellations . . . . . . . . . . . 30
             2.6.2.  Resumption . . . . . . . . . . . . . . . . . . . 32
       2.7.  IOTP Wallet Initialization . . . . . . . . . . . . . . . 33
       2.8.  Payment Software Management. . . . . . . . . . . . . . . 34
   3.  Mutuality. . . . . . . . . . . . . . . . . . . . . . . . . . . 34
       3.1.  Error Codes. . . . . . . . . . . . . . . . . . . . . . . 38
       3.2.  Attributes and Elements. . . . . . . . . . . . . . . . . 48
       3.3.  Process States . . . . . . . . . . . . . . . . . . . . . 61
             3.3.1.  Merchant . . . . . . . . . . . . . . . . . . . . 61
             3.3.2.  Consumer . . . . . . . . . . . . . . . . . . . . 63
             3.3.3.  Payment Handler. . . . . . . . . . . . . . . . . 65
   4.  Payment API Calls. . . . . . . . . . . . . . . . . . . . . . . 66
       4.1.  Brand Compilation Related API Calls. . . . . . . . . . . 66
             4.1.1.  Find Accepted Payment Brand. . . . . . . . . . . 66
             4.1.2.  Find Accepted Payment Protocol . . . . . . . . . 68
             4.1.3.  Get Payment Initialization Data. . . . . . . . . 70
             4.1.4.  Inquire Authentication Challenge . . . . . . . . 72
             4.1.5.  Authenticate . . . . . . . . . . . . . . . . . . 73
             4.1.6.  Check Authentication Response. . . . . . . . . . 74
       4.2.  Brand Selection Related API Calls. . . . . . . . . . . . 76
             4.2.1.  Find Payment Instrument. . . . . . . . . . . . . 76
             4.2.2.  Check Payment Possibility. . . . . . . . . . . . 78
       4.3.  Payment Transaction Related API calls. . . . . . . . . . 80
             4.3.1.  Start Payment Consumer . . . . . . . . . . . . . 80
             4.3.2.  Start Payment Payment Handler. . . . . . . . . . 82
             4.3.3.  Resume Payment Consumer. . . . . . . . . . . . . 84
             4.3.4.  Resume Payment Payment Handler . . . . . . . . . 85
             4.3.5.  Continue Process . . . . . . . . . . . . . . . . 86
             4.3.6.  Change Process State . . . . . . . . . . . . . . 88
       4.4.  General Inquiry API Calls. . . . . . . . . . . . . . . . 89
             4.4.1.  Remove Payment Log . . . . . . . . . . . . . . . 90
             4.4.2.  Payment Instrument Inquiry . . . . . . . . . . . 90
             4.4.3.  Inquire Pending Payment. . . . . . . . . . . . . 92
       4.5.  Payment Related Inquiry API Calls. . . . . . . . . . . . 93
             4.5.1.  Check Payment Receipt. . . . . . . . . . . . . . 93
             4.5.2.  Expand Payment Receipt . . . . . . . . . . . . . 94
             4.5.3.  Inquire Process State. . . . . . . . . . . . . . 96
             4.5.4.  Start Payment Inquiry. . . . . . . . . . . . . . 97
             4.5.5.  Inquire Payment Status . . . . . . . . . . . . . 98
       4.6.  Other API Calls. . . . . . . . . . . . . . . . . . . . . 99
             4.6.1.  Manage Payment Software. . . . . . . . . . . . . 99
   5.  Call Back Function . . . . . . . . . . . . . . . . . . . . . .101
   6.  Security Considerations. . . . . . . . . . . . . . . . . . . .103
   7.  References . . . . . . . . . . . . . . . . . . . . . . . . . .103
       7.1.  Normative References . . . . . . . . . . . . . . . . . .103
       7.2.  Informative References . . . . . . . . . . . . . . . . .104
   Acknowledgement. . . . . . . . . . . . . . . . . . . . . . . . . .105
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . .105
   Full Copyright Statement . . . . . . . . . . . . . . . . . . . . .106

1. Introduction

Common network technologies are based on standardized and established Internet technologies. The Internet technologies provide mechanisms and tools for presentation, application development, network infrastructure, security, and basic data exchange.

Due to the presence of already installed trading roles' systems with their own interfaces (Internet shop, order management, payment, billing, and delivery management systems, or financial institute's legacy systems), IOTP has been limited to the common external interface over the Internet. However, some of these internal interfaces might be also standardized for better integration of IOTP aware components with of the existing infrastructure and its cost effective reuse. For more information on IOTP, see [IOTP] and [IOTPBOOK].

The typical Payment Handlers (i.e., financial institutes or near-bank organizations) as well as Merchants require an IOTP aware application that easily fits into their existing financial infrastructure. The Payment Handler might even insist on the reuse of special in-house solutions for some subtasks of the IOTP aware application, e.g., reflecting their cryptography modules, gateway interfaces, or physical environment. Therefore, their IOTP aware implementation really requires such clear internal interfaces.

More important, consumers demand modularization and clear internal interfaces: Their IOTP application aims at the support of multiple payment methods. Consumers prefer the flexible use of different seamless integrating payment methods within one trading application with nearly identical behavior and user interface. The existence of a well-defined interface enables payment software developers to bolt on their components to other developer's general IOTP Application Core. Initially, this consideration leads to the two-level layered view of the IOTP software for each role, consisting of:

   o  some generic IOTP system component, the so-called IOTP application
      core - providing IOTP based gateway services and generic business
      logic and
   o  the trading roles' specific back-end systems implementing the
      specific trading transaction types' functionality.

In order to isolate the changes on the infrastructure, the IOTP trading application has been three-layered:

   o  the IOTP Application Core processes the generic parts of the IOTP
      transaction and holds the connection to the Internet,
   o  the Existing Legacy System or Existing Payment Software which
      processes the actual transaction type, and particular payment
      transaction, and
   o  the IOTP Middle-ware or IOTP Payment Bridge which glues the other
      two possibly incompatible components.  It brokers between the
      specific interface of the Existing Legacy System and the
      standardized interfaces of the IOTP Application Core.

As IOTP extends payment schemes to a trading scheme, primarily, this document focuses on payment modules, i.e., the interface between the IOTP Payment Bridge and the IOTP Application Core. It provides a standard method for exchanging payment protocol messages between the parties involved in a payment. But, it does not specify any interface for order or delivery processing.

Such a Payment Application Programmers Interface (API) must suit for a broad range of payment methods: (1) software based like Credit Card SET or CyberCoin, (2) chip card based like Mondex or GeldKarte, and (3) mimicries of typical and traditional payment methods like money transfer, direct debit, deposit, withdrawal, money exchange and value points. It should support both payments with explicit consumer acknowledge and automatic repeated payments, which have been consumer approved in advance. For more information on SET, see [SET].

The following discussion focuses on the Consumer's point of view and uses the associated terminology. When switching to Merchants' or Delivery Handlers' IOTP aware applications, the payment related components should be implicitly renamed by Existing Legacy Systems to the IOTP Middle-ware. The next two sub-sections describe the general payment scenario and several assumptions about the coarsely sketched software components.

Section 2 illustrates the payment transaction progress and message flow of different kinds of transaction behavior. Sections 3 to 4 provide the details of the API functions and Section 5 elaborates the call back interface.

1.1. General payment phases

The following table sketches the four logical steps of many payment schemes. The preceding agreements about the goods, payment method, purchase amount, or delivery rules are omitted.
   Payment State  Party             Example Behavior
   -------------  -----             ----------------
   Mutual         Payment Handler   Generation of identification
   Authentication                   request, solvency request, or
   and                              some nonce
   Initialization Consumer          Responses to the requests and
                                    generation of own nonce
   Authorization  Payment Handler   Generation of the authorization
                                    request (for consumer)
                  Consumer          Agreement to payment (by
                                    reservation of the Consumer's
                                    e-money)
                  Payment Handler   Acceptance or rejection of the
                                    agreement (consumer's
                                    authorization response),
                                    generation of the authorization
                                    request (for issuer/acquirer),
                                    and processing of its response
   Capture                          Generation of the capture
                                    request (for issuer/acquirer)
                  Consumer          Is charged
                  Payment Handler   Acceptance or rejection of the
                                    e-money, close of the payment
                                    transaction
   Reversal                         On rejection (online/delayed):
                                    generation of the reversal data
                  Consumer          Receipt of the refund
However, some payment schemes:
   o  limit themselves to one-sided authentication,
   o  perform off-line authorization without any referral to any
      issuer/acquirer,
   o  apply capture processing in batch mode, or
   o  do not distinguish between authorization and capture,
   o  lack an inbound mechanism for reversals or implement a limited
      variant.

This model applies not only to payments at the typical points of sales but extends to refunds, deposits, withdrawals, electronic cheques, direct debits, and money transfers.

1.2. Assumptions

In outline, the IOTP Payment Bridge processes some input sequence of payment protocol messages being forwarded by the IOTP Application Core. It (1) disassembles the messages, (2) maps them onto the formats of the Existing Payment Software, (3) assembles its responses, and (4) returns another sequence of payment protocol messages that is mostly intended for transparent transmission by the IOTP Application Core to some IOTP aware remote party. Normally, this process continues between the two parties until the Payment Handler's Payment API signals the payment termination. Exceptionally, each system component may signal failures.

The relationship between the aforementioned components is illustrated in the following figure. These components might be related to each other in a flexible n-to-m-manner:

   o  One IOTP Application Core may manage multiple IOTP Payment Bridges
      and the latter might be shared between multiple IOTP Application
      Cores.
   o  Each Payment Bridge may manage multiple Existing Payment Software
      modules and the latter might be shared between multiple Payment
      Bridges.
   o  Each Existing Payment Software may manage multiple payment schemes
      (e.g., SET) and the latter might be supported by multiple Existing
      Payment Software modules.  For more information on SET see [SET].
   o  Each payment scheme may support multiple payment instruments
      (e.g., particular card) or methods (e.g., Visa via SET) and the
      latter might be shared by multiple Existing Payment Software
      Components.
   *+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*
   IOTP client (consumer)  <--------------->  IOTP server (merchant)
   (      contains             Internet       (      contains
   IOTP Application Core)                     IOTP Application Core)
         ^                                          ^
         | IOTP Payment                             | IOTP Payment
         |    API                                   |    API
         v                                          v
   IOTP Payment Bridge                        IOTP Payment Bridge
        ^                                           ^
        | Existing Payment APIs, e.g.,              |
        | SET, Mondex, etc.                         |
        v                                           v
   Existing Payment Software               Existing Payment Software
   *+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*
                 Figure 1: Relationship of the Components

The Payment API considers the following transaction types of Baseline IOTP:

      o  Baseline Purchase,
      o  Baseline Refund,
      o  Baseline Value Exchange,
      o  Baseline Withdrawal, and
      o  Baseline (Payment) Inquiry.

For more information on Baseline IOTP, see [IOTP] and [IOTPBOOK].

First, the authors' vision of the IOTP aware application's and its main components' capabilities are clarified: On the one hand, the Payment API should be quite powerful and flexible for sufficient connection of the generic and specific components. On the other hand, the Payment API should not be overloaded with nice-to-haves being unsupported by Existing Payment Software.

Despite the strong similarities on the processing of successful payments, failure resolution and inquiry capabilities differ extremely among different payment schemes. These aspects may even vary between different payment instrument using the same payment schemes. Additionally, the specific requirements of Consumers, Merchants and Payment Handlers add variance and complexity. Therefore, it is envisioned that the IOTP Application Core provides only very basic inquiry mechanisms while complex and payment scheme specific inquiries, failure analysis, and failure resolution are fully deferred to the actual Existing Payment Software - including the user interface. The IOTP Application Core processes payments transparently, i.e., it forwards the wrapped payment scheme specific messages to the associated IOTP Payment Bridge/Existing Payment Software. The Existing Payment Software might even use these messages for inbound failure resolution. It reports only the final payment status to the IOTP Application Core or some intermediate - might be also final - status on abnormal interruption.

The IOTP Application Core implements the generic and payment scheme independent part of the IOTP transaction processing and provides the suitable user interface. Focusing on payment related tasks, it

   o  manages the registered IOTP Payment Bridges and provides a
      mechanism for their registration - the latter is omitted by this
      document.
   o  assumes that any IOTP Payment Bridge is a passive component, i.e.,
      it strictly awaits input data and generates one response to each
      request,
   o  supports the payment negotiation (Consumer: selection of the
      actual payment instrument or method; Merchant: selection of the
      payment methods being offered to the Consumer) preceding the
      payment request,
   o  requests additional payment specific support from the Existing
      Payment Software via the selected and registered the IOTP Payment
      Bridge,
   o  initializes and terminates the Existing Payment Software via the
      IOTP Payment Bridge,
   o  inquires authentication data (for subsequent request or response)
      from the Existing Payment Software, specific authentication
      component - omitted in this document - or Consumer (by a suitable
      user interface),

o supervises the online transaction process and traces its progress,

   o  stores the transaction data being exchanged over the IOTP wire -
      payment scheme specific data is handled transparently,
   o  relates each payment transaction with multiple payment parameters
      (IOTP Transaction Identifier, Trading Protocol Options, Payment
      Instrument/Method, Offer Response, IOTP Payment Bridge, and Wallet
      Identifier, associated remote Parties).  The relation might be
      lowered to the party's Payment Identifier, IOTP Payment Bridge,
      Wallet Identifier, and the remote parties when the actual payment
      transaction has been successfully started.
   o  implements a payment transaction progress indicator,

o enables the inquiry of pending and completed payment transactions,

   o  implements generic dialogs, e.g., brand selection, payment
      acknowledge, payment suspension / cancellation, receipt
      visualization, basic transaction inquiry, balance inquiry, or
      receipt validation,
   o  defers payment specific processing, supervision, validation, and
      error resolution to the Existing Payment Software.  It is
      expected, that the Existing Payment Software will try to resolve
      many errors first by the extended exchange of Payment Exchange
      messages.  The most significant and visible failures arise from
      sudden unavailability or lapses of the local or opposing payment
      component.
   o  supports the invocation of any Existing Payment Software in an
      interactive mode, which might be used (1) for the payment scheme
      specific post-processing of a (set of) payment transactions, (2)
      for the analysis of a payment instrument, (3) for the registration
      of a new payment instrument/scheme, or (4) re-configuration of a
      payment instrument/scheme.
   o  exports call back functions for use by the IOTP Payment Bridge or
      Existing Payment Software for progress indication.
   In addition, the IOTP Application Core
   o  manages the IOTP message components and IOTP message blocks
      exchanged during the transaction which may be referenced and
      accessed during the processing of subsequent messages, e.g., for
      signature verification.  In particular, it stores named Packaged
      Content elements exchanged during payments.
   o  manages several kinds of identifiers, i.e., transaction, message,
      component, and block identifiers,
   o  implements a message caching mechanism,
   o  detects time-outs at the protocol and API level reflecting the
      communication with both the IOTP aware remote party and the
      Payment API aware local periphery, e.g., chip card (reader) may
      raise time-outs.
However, the IOTP Payment Bridge and Existing Payment Software do not have to rely on all of these IOTP Application Core's capabilities. E.g., some Consumer's Existing Payment Software may refuse the disclosure of specific payment instruments at brand selection time and may delay this selection to the "Check Payment Possibility" invocation using its own user interface.

The IOTP Payment Bridge's capabilities do not only deal with actual payments between the Consumer and the Payment Handler but extend to the following:

   o  translation and (dis)assemblage of messages between the formats of
      the IOTP Payment API and those of the Existing Payment Software.
      Payment API requests and response are strictly 1-to-1 related.
   o  Consumer's payment instrument selection by the means of an
      unsecured/public export of the relationship of payment brands,
      payment protocols, and payment instruments (identifiers).
      Generally, this includes not just the brand (Mondex, GeldKarte,
      etc.) but also which specific instance of the instrument and
      currency to use (e.g., which specific Mondex card and which
      currency of all those available).

However, some Existing Payment Software may defer the selection of the payment instrument to the actual payment carrying-out or it may even lack any management of payment instruments. E.g., chip card based payment methods may offer - Point of Sale like - implicit selection of the payment instrument by simple insertion of the chip card into the chip card reader or it interrogates the inserted card and requests an acknowledge (or selection) of the detected payment instrument(s).

   o  payment progress checks, e.g., is there enough funds available to
      carry out the purchase, or enough funds left for the refund,
   o  IOTP Payment Receipt checks which might be performed over its
      Packaged Content or by other means.
   o  recoding of payment scheme specific receipts into a format which
      can be displayed to the user or printed,

o cancellation of payment, even though it is not complete,

   o  suspension and resumption of payment transactions.  Two kinds of
      failures the Existing Payment Software might deal with are (1) the
      time-out of the network connection and (2) lack of funds.  For
      resolution, the IOTP Application Core may try the suspension with
      a view to later possible resumption.
   o  recording the payment progress and status on a database.  E.g.,
      information about pending payments might be used to assist their
      continuation when the next payment protocol message is received.
   o  payment transaction status inquiry, so that the inquirer - IOTP
      Application Core or User - can determine the appropriate next
      step.
   o  balance inquiry or transaction history, e.g., consumers may
      interrogate their chip card based payment instrument or remotely
      administer some account in advance of a payment transaction
      acknowledge,
   o  inquiry on abnormal interrupted payment transactions, which might
      be used by the IOTP Application Core to resolve these pending
      transactions at startup (after power failure).
   o  payment progress indication.  This could be used to inform the end
      user of details on what is happening with the payment.

o payment method specific authentication methods.

Existing Payment Software may not provide full support of these capabilities. E.g., some payment schemes may not support or may even prevent the explicit transaction cancellation at arbitrary phases of the payment process. In this case, the IOTP Payment Bridge has to implement at least skeletons that signal such lack of support by the use of specific error codes (see below).

The Existing Payment Software's capabilities vary extremely. It

   o  supports payment scheme specific processing, supervision,
      validation, and error resolution.  It is expected, that many
      errors are tried to be resolved first by the extended exchange of
      Payment Exchange messages.
   o  provides hints for out-of-band failure resolution on failed
      inbound resolution - inbound resolution is invisible to the IOTP
      Application Core.
   o  may implement arbitrary transaction data management and inquiry
      mechanisms ranging from no transaction recording, last transaction
      recording, chip card deferred transaction recording, simple
      transaction history to sophisticated persistent data management
      with flexible user inquiry capabilities.  The latter is required
      by Payment Handlers for easy and cost effective failure
      resolution.
o implements the payment scheme specific dialog boxes.

Even the generic dialog boxes of the IOTP Application Core might be unsuitable: Particular (business or scheme) rules may require some dedicated appearance / structure / content or the dialog boxes, may prohibit the unsecured export of payment instruments, or may prescribe the pass phrase input under its own control.

2. Message Flow

The following lists all functions of the IOTP Payment API:
      o  Brand Compilation Related API Functions

"Find Accepted Payment Brand" identifies the accepted payment brands for any indicated currency amount.

"Find Accepted Payment Protocol" identifies the accepted payment protocols for any indicated currency amount (and brand) and returns payment scheme specific packaged content for brand selection purposes.

This function might be used in conjunction with the aforementioned function or called without any brand identifier.

"Get Payment Initialization Data" returns additional payment scheme specific packaged content for payment processing by the payment handler.

"Inquire Authentication Challenge" returns the payment scheme specific authentication challenge value.

"Check Authentication Response" verifies the returned payment scheme specific authentication response value.

"Change Process State" is used (here only) for abnormal termination. (cf. Payment Processing Related API Functions).

      o  Brand Selection Related API Functions

"Find Payment Instrument" identifies which instances of a payment instrument of a particular payment brand are available for use in a payment.

"Check Payment Possibility" checks whether a specific payment instrument is able to perform a payment. "Authenticate" forwards any payment scheme specific authentication data to the IOTP Payment Bridge for processing.

"Change Process State" is used (here only) for abnormal termination. (cf. Payment Processing Related API Functions).

      o  Payment Processing Related API Functions

"Start or Resume Payment Consumer/Payment Handler" initiate or resume a payment transaction. There exist specific API functions for the two trading roles Consumer and Payment Handler.

"Continue Process" forwards payment scheme specific data to the Existing Payment Software and returns more payment scheme specific data for transmission to the counter party.

"Change Process State" changes the current status of payment transactions. Typically, this call is used for termination or suspension without success.

      o  General Inquiry API Functions

"Remove Payment Log" notifies the IOTP Payment Bridge that a particular entry has been removed from the Payment Log of the IOTP Application Core.

"Payment Instrument Inquiry" retrieves the properties of Payment Instruments.

"Inquire Pending Payment" reports any abnormal interrupted payment transaction known by the IOTP Payment Bridge.

   Payment Processing Related Inquiry API Functions

"Check Payment Receipt" checks the consistency and validity of IOTP Payment Receipts, received from the Payment Handler or returned by "Inquire Process State" API calls. Typically, this function is called by the Consumer during the final processing of payment transactions. Nevertheless, this check might be advantageous both for Consumers and Payment Handlers on failure resolution.

"Expand Payment Receipt" expands the Packaged Content of IOTP Payment Receipts as well as payment scheme specific payment receipts into a form which can be used for display or printing purposes.

"Inquire Process State" responds with the payment state and the IOTP Payment Receipt Component. Normally, this function is called by the Payment Handler for final processing of the payment transaction. "Start Payment Inquiry" prepares the remote inquiry of the payment transaction status and responds with payment scheme specific data that might be needed by the Payment Handler for the Consumer initiated inquiry processing.

"Inquire Payment Status" is called by the Payment Handler on Consumer initiated inquiry requests. This function returns the payment scheme specific content of the Inquiry Response Block.

"Continue Process" and "Change Process State" (cf. Payment Processing Related API Calls)

      o  Other API Functions

"Manage Payment Software" enables the immediate activation of the Existing Payment Software. Further user input is under control of the Existing Payment Software.

"Call Back" provides a general interface for the visualization of transaction progress by the IOTP Application Core.

The following table shows which API functions must (+), should (#), or might (?) be implemented by which Trading Roles.

   API function                  Consumer  Payment Handler  Merchant
   ------------                  --------  ---------------  --------
   Find Accepted Payment Brand                                 +
   Find Accepted Payment Protocol                              #
   Find Payment Instrument          +
   Get Payment Initialization Data                             +
   Check Payment Possibility        +
   Start Payment Consumer           +
   Start Payment Payment Handler                  +
   Resume Payment Consumer          #
   Resume Payment Payment Handler                 #
   Continue Process                 +             +
   Inquire Process State            +             +            ?
   Change Process State             +             +            ?
   Check Payment Receipt            +             ?
   Expand Payment Receipt           #             ?
   Remove Payment Log               ?             ?            ?
   Inquire Authentication Challenge                            ?
   Authenticate                     +
   Check Authentication Response                               ?
   Payment Instrument Inquiry       ?
   Inquire Pending Payment          #             #
   Start Payment Inquiry            ?
   Inquire Payment Status                         ?
   Manage Payment Software          #             ?            ?
   Call Back                        #
        Table 1: Requirements on API Functions by the Trading Roles

The next sections sketch the relationships and the dependencies between the API functions. They provide the informal description of the progress alternatives and depict the communication and synchronization between the general IOTP Application Core and the payment scheme specific modules.

2.1. Authentication Documentation Exchange

This section describes how the functions in this document are used together to process authentication.
   *+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*
   Authenticator   Inquire Authentication Challenge(Alg1*)   -> IPB
                   Inq. Auth. Challenge Response(Alg1,Ch1)   <- IPB
                   . . .
                   Inquire Authentication Challenge(Algn*)   -> IPB
                   Inq. Auth. Challenge Response(Algn,Chn)   <- IPB
                   Create and transmit Authentication Request Block
   Authenticatee   Authenticate(Alg1, Ch1)                   -> IPB
                   AuthenticateResponse(...)                 <- IPB
                   . . .
                   Authenticate(Algm, Chm)                   -> IPB
                   AuthenticateResponse(Res)                 <- IPB
                   Create and transmit Authentication Response Block
   Authenticator   Check Authentication Response(Algm,Chm,Res)->IPB
                   Check Auth. Response()                     <-IPB
                   Create and transmit Authentication Status Block
   *+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*
                  Figure 2. Authentication Message Flows
   1. (Authenticator Process) None, one or multiple IOTP Payment Bridges
      (IPB) are requested for one or multiple authentication challenge
      values ("Inquire Authentication Challenge").  Each value is
      encapsulated in an IOTP Authentication Request Component.  In
      addition, the IOTP Application Core may add payment scheme
      independent authentication methods.  All of them form the final
      IOTP Authentication Request Block, which describes the set of
      authentication methods being supported by the authenticator and
      from which the Authenticatee has to choose one method.
      Note that the interface of the API function is limited to the
      response of exactly one algorithm per call.  If the IOTP
      Application Core provides a choice of algorithms for input, this
      choice should be reduced successively by the returned algorithm
      ({Alg(i+1)*} is subset of {Algi*}).
      During the registration of new Payment Instruments, the IOTP
      Payment Bridge notifies the IOTP Application Core about the
      supported authentication algorithms.
   2. On the presence of an IOTP Authentication Block within the
      received IOTP message, the Authenticatee's IOTP Application Core
      checks whether the IOTP transaction type in the current phase
      actually supports the authentication process.
      For each provided Authentication Request Component, the IOTP
      Application Core analyzes the algorithms' names, the transaction
      context, and optionally user preferences in order to determine the
      system components which are capable to process the authentication
      request items.  Such system components might be the IOTP
      Application Core itself or any of the registered IOTP Payment
      Bridges.
      Subsequently, the IOTP Application Core requests the responses to
      the supplied challenges from the determined system components in
      any order.  The authentication trials stop with the first
      successful response, which is included in the IOTP Authentication
      Response Block.
      Alternatively, the IOTP Application might ask for a user
      selection.  This might be appropriate, if two or more
      authentication algorithms are received that require explicit user
      interaction, like PIN or chip card insertion.
      The Authenticatee's organizational data is requested by an IOTP
      Authentication Request Block without any content element.  On
      failure, the authentication (sequence) might be retried, or the
      whole transaction might be suspended or cancelled.
   3. (Authenticator Process) The IOTP Application Core checks the
      presence of the IOTP Authentication Response Component in the
      Authentication Response Block and forwards its content to the
      generator of the associated authentication challenge for
      verification ("Check Authentication Response").
      On sole organizational data request, its presence is checked.
      Any verification must succeed in order to proceed with the
      transaction.

2.2. Brand Compilation

The following shows how the API functions are used together so that the Merchant can (1) compile the Brand List Component, (2) generate the Payment Component, and (3) adjust the Order Component with payment scheme specific packaged content.
   *+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*
   Merchant      For each registered IOTP Payment Bridge
                 |  Find Accepted Payment Brand()             -> IPB
                 |  Find Accepted Payment Brand Response (B*) <- IPB
                 |  Find Accepted Payment Protocol(B1)        -> IPB
                 |  Find Accepted Payment Protocol Res.(P1*)  <- IPB
                 |  . . .
                 |  Find Accepted Payment Protocol(Bn)        -> IPB
                 |  Find Accepted Payment Protocol Res.(Pn*)  <- IPB
                 Create one Brand List Component, ideally sharing
                   common Brand, Protocol Amount, Currency Amount,
                   and Pay Protocol Elements
                 Create Trading Protocol Options Block
                 On brand independent transactions
                 |  Create Brand Selection Component, implicitly
                 |  Get Payment Initialization Data(B1,P1)   -> IPB
                 |  Get Payment Initialization Data Res.()   <- IPB
                 |  Optionally
                 |  |  Inquire Process State()               -> IPB
                 |  |  Inquire Process State Response(State) <- IPB
                 |  Create Offer Response Block
                 Transmit newly created Block(s)
   Consumer      Consumer selects Brand (Bi)/Currency/Protocol (Pj)
                   from those that will work and generates Brand
                   Selection Component - at least logically
                 On brand dependent transaction
                 |  Transmit Brand Selection Component
   Merchant      On brand dependent transaction
                 |  Get Payment Initialization Data(Bi,Pj)   -> IPB
                 |  Get Payment Initialization Data Res.()   <- IPB
                 |  Optionally
                 |  |  Inquire Process State()               -> IPB
                 |  |  Inquire Process State Response(State) <- IPB
                 |  Create Offer Response Block
                 |  Transmit newly created Block
   *+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*
                 Figure 3. Brand Compilation Message Flows
   1.  The Merchant's commerce server controls the shopping dialog with
       its own mechanisms until the Consumer checks out the shopping
       cart and indicates the payment intention.  The notion shopping
       subsumes any non-IOTP based visit of the Merchant Trading Role's
       (which subsumes Financial Institutes) web site in order to
       negotiate the content of the IOTP Order Component.  The
       subsequent processing switches to the IOTP based form by the
       activation of the Merchant's IOTP aware application.
   2.  The IOTP Application Core inquires for the IOTP level trading
       parameters (Consumer's shopping identifier, payment direction,
       initial currency amounts, discount rates, Merchant's and Delivery
       Handler's Net Locations, Non-Payment Handler's Organizational
       Data, initial order information, ....).
   3.  The registered IOTP Payment Bridges are inquired by the IOTP
       Application Core about the accepted payment brands ("Find
       Accepted Payment Brand").  Their responses provide most of the
       attribute values for the compilation of the Brand List
       Component's Brand Elements.  The IOTP Application Core might
       optionally match the returned payment brands with Merchant's
       general preferences.
       The IOTP Application Core must provide any wallet identifiers, if
       they are required by the IOTP Payment Bridges which signal their
       need by specific error codes (see below).  Any signaled error
       that could not be immediately solved by the IOTP Application Core
       should be logged - this applies also to the subsequent API calls
       of this section.  In this case, the IOTP Application Core creates
       an IOTP Error Block (hard error), transmits it to the Consumer,
       and terminates the current transaction.
   4.  The IOTP Application Core interrogates the IOTP Payment Bridges
       for each accepted payment brand about the supported payment
       protocols ("Find Accepted Payment Protocol").  These responses
       provide the remaining attribute values of the Brand Elements as
       well as all attribute values for the compilation of the Brand
       List Component's Protocol Amount and Pay Protocol Elements.
       Furthermore, the organisational data about the Payment Handler is
       returned.  The IOTP Application Core might optionally match the
       returned payment brands with Merchant's general preferences.
       Alternatively, the IOTP Application Core might skip the calls of
       "Find Accepted Payment Brands" (cf. Step 3) and issue the "Find
       Accepted Payment Protocol" call without any Brand given on the
       input parameter list.  In this case, the IOTP Payment Bridge
       responds to the latter call with the whole set of payment schemes
       supported w.r.t. the other input parameters.
   5.  The steps 3 and 4 are repeated during IOTP Value Exchange
       transactions - these steps are omitted in the previous figure.
   6.  The IOTP Application Core compiles the Brand List Component(s)
       and the IOTP Trading Protocol Options Block.  It is recommended
       that the "equal" items returned by IOTP Payment Bridge function
       calls are shared due to the extensive linking capabilities within
       the Brand List Component.  However, the compilation must consider
       several aspects in order to prevent conflicts - sharing detection
       might be textual matching (after normalization):
      o  Packaged Content Elements contained in the Brand List Component
         (and subsequently generated Payment and Order Components) might
         be payment scheme specific and might depend on each other.
      o  Currently, IOTP lacks precise rules for the content of the
         Packaged Content Element.  Therefore, transaction / brand /
         protocol / currency amount (in)dependent data might share the
         same Packaged Content Element or might spread across multiple
         Packaged Content Elements.
      o  The Consumer's IOTP Application Core transparently passes the
         Packaged Content Elements to the IOTP Payment Bridges which
         might not be able to handle payment scheme data of other
         payment schemes, accurately.
       The rules and mechanisms of how this could be accomplished are
       out of the scope of this document.  Furthermore, this document
       does not define any further restriction to the IOTP
       specification.
   7.  The IOTP Application Core determines whether the IOTP message can
       be enriched with an Offer Response Block.  This is valid under
       the following conditions:
      o  All payment alternatives share the attribute values and
         Packaged Content Elements of the subsequently generated IOTP
         Payment and Order Components.
      o  The subsequently generated data does not depend on any IOTP
         BrandSelInfo Elements that might be reported by the consumer
         within the TPO Selection Block in the brand dependent variant.
       If both conditions are fulfilled, the IOTP Application Core might
       request the remaining payment scheme specific payment
       initialization data from the IOTP Payment Bridge ("Get Payment
       Initialization Data") and compile the IOTP Offer Response Block.
       Optionally, the IOTP Application Core might request the current
       process state from the IOTP Payment Bridge and add the inferred
       order status to the IOTP Offer Response Block.  Alternatively,
       IOTP Application might determine the order status on its own.
       As in step 6, the rules and mechanisms of how this could be
       accomplished are out of the scope of this document.
   8.  The IOTP Application Core compiles the IOTP TPO Message including
       all compiled IOTP Blocks and transmits the message to the
       Consumer.  The IOTP Application Core terminates if an IOTP Offer
       Response Block has been created.
   9.  The Consumer performs the Brand Selection Steps (cf. Section 2.3)
       and responds with a TPO Selection Block if no IOTP Offer Response
       Block has been received.  Otherwise, the following step is
       skipped.
   10. On brand dependent transactions, the IOTP Application Core
       requests the remaining payment scheme specific payment
       initialization data from the IOTP Payment Bridge ("Get Payment
       Initialization Data"), compiles the IOTP Offer Response Block,
       transmits it to the Consumer, and terminates.  Like Step 7, the
       IOTP Application Core might access the current process state of
       the IOTP Payment Bridge for the compilation of the order status.

Any error during this process raises an IOTP Error Block.

2.3. Brand Selection

This section describes the steps that happen mainly after the Merchant's Brand Compilation (in a brand independent transaction). However, these steps might partially interlace the previous process (in a brand dependent transaction).
   *+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*
   Merchant      Merchant generates Brand List(s) containing
                   Brands, Payment Protocols and Currency Amounts
                 On brand independent transactions
                 |  Merchant generates Offer Response Block
   Consumer      Compile set(s) of Brands B/Protocols P
                 for each set
                 |  Find Payment Instrument(B, P, C)        -> IPB
                 |  Find Payment Instrument Response (PI*)    <- IPB
                 Consumer selects Brand/Currency/Payment Instrument
                   from those that will work and generates Brand
                   Selection Component
                 For the Selection
                 |  Get Payment Initialization Data(B,C,PI,P) -> IPB
                 |  Get Payment Initialization Data Response()<- IPB
                 On brand dependent transaction
                 |  Generate and transmit TPO Selection Block
   Merchant      On brand dependent transaction
                 |  Merchant checks Brand Selection and generates
                 |  and transmits Offer Response Block
   *+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*
                  Figure 4. Brand Selection Message Flows
   1. The Merchant's commerce server controls the shopping dialog with
      its own mechanisms until the Consumer checks out the shopping cart
      and indicates his payment intention.  The subsequent processing
      switches to the IOTP based form by the activation of the
      Merchant's IOTP aware application.
   2. The IOTP Application Core compiles the IOTP Trading Protocol
      Options Block which contains the IOTP Brand List Component(s)
      enumerating Merchant's accepted payment brands and payment
      protocols and initiates the Brand Selection process.
   3. This first IOTP message activates the Consumer's IOTP aware
      application, e.g., the Web browser invokes a helper application
      (e.g., Java applet or external application).  Its IOTP Application
      Core
      o  infers the accepted payment brands, payment protocols, payment
         direction, currencies, payment amounts, any descriptions etc.,
         and their relationships from the IOTP message,
      o  determines the registered IOTP Payment Bridges,
      o  compiles one or multiple sets of brand and protocol such that
         the join of all sets describes exactly the payment alternatives
         being offered by the Merchant.
      o  inquires payment (protocol) support and the known payment
         instruments from each registered IOTP Payment Bridge for each
         compiled set ("Find Payment Instrument").  However, some IOTP
         Payment Bridges may refuse payment instrument distinction.
      The payment protocol support may differ between payment
      instruments if the IOTP Payment Bridge supports payment instrument
      distinction.
      These API calls are used to infer the payment alternatives at the
      startup of any payment transaction (without user unfriendly
      explicit user interaction).
      The IOTP Application Core must provide wallet identifiers, if they
      are requested by the IOTP Payment Bridges which signal their need
      by specific error codes (see below).
      It is recommended that the IOTP Application Core manages wallet
      identifiers.  But for security reasons, it should store pass
      phrases in plain text only in runtime memory.  Developers of IOTP
      Payment Bridges and payment software modules should provide a thin
      and fast implementation - without lengthy initialization processes
      - for this initial inquiry step.
   4. The IOTP Application Core verifies the Consumer's payment
      capabilities with the Merchant's accepted payment brands and
      currencies,
      o  displays the valid payment instruments and payment instrument
         independent payment brands (brand and protocol) together with
         their purchase parameters (payment direction, currency,
         amount), and
      o  requests the Consumer's choice or derives it automatically from
         any configured preferences.  Any selection ties one IOTP
         Payment Bridge with the following payment transaction.
      The handling and resolution of unavailable IOTP Payment Bridges
      during the inquiry in Step 3 is up to the IOTP Application Core.
      It may skip these IOTP Payment Bridges or may allow user supported
      resolution.
      Furthermore, it may offer the registration of new payment
      instruments when the Consumer is asked for payment instrument
      selection.
   5. The IOTP Application Core interrogates the fixed IOTP Payment
      Bridge whether the payment might complete with success ("Check
      Payment Possibility").  At this step, the IOTP Payment Bridge may
      issue several signals, e.g.,
      o  payment can proceed immediately,
      o  required peripheral inclusive of some required physical payment
         instrument (chip card) is unavailable,
      o  (non-IOTP) remote party (e.g., issuer, server wallet) is not
         available,
      o  wallet identifier or pass phrase is required,
      o  expired payment instrument (or certificate), insufficient
         funds, or
      o  physical payment instrument unreadable.
      In any erroneous case, the user should be notified and offered
      accurate alternatives.  Most probably, the user might be offered
      o  to resolve the problem, e.g., to insert another payment
         instrument or to verify the periphery,
      o  to proceed (assuming its success),
      o  to cancel the whole transaction, or
      o  to suspend the transaction, e.g., initiating a nested
         transaction for uploading an electronic purse.
      If the payment software implements payment instrument selection on
      its own, it may request the Consumer's choice at this step.
      If the check succeeds, it returns several IOTP Brand Selection
      Info Elements.
   6. The Steps 2 to 5 are repeated and possibly interlaced for the
      selection of the second payment instrument during IOTP Value
      Exchange transactions - this is omitted in the figure above.
   7. The IOTP Brand Selection Component is generated and enriched with
      the Brand Selection Info elements.  This component is transmitted
      to the Merchant inside a TPO Selection Block if the received IOTP
      message lacks the IOTP Offer Response Block.  The Merchant will
      then respond with an IOTP Offer Response Block (following the
      aforementioned compilation rules).

2.4. Successful Payment

An example of how the functions in this document are used together to effect a successful payment is illustrated in the Figure 5. In the figure 5, PS0, PS1, ..., and PSn indicate the nth PayScheme Packaged Content data, and [ ] indicates optional.

(Technically, two payments happen during IOTP Value Exchange transactions.)

   *+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*
   Consumer        Start Payment Consumer(Amount,[PS0]...)    -> IPB
                   Start Payment Cons. Res.([PS1], CS=Cont.)  <- IPB
                   Create and transmit Payment Request Block
   Payment Handler Start Payment Pay. Handler(Amount, [PS1])  -> IPB
                   Start Payment PH Response(PS2, CS=Cont.)   <- IPB
                   Create and transmit Payment Exchange Block
   Consumer        Continue Process(PS2)                      -> IPB
                   Continue Process Response(PS3, CS=Cont.)   <- IPB
            ... CONTINUE SWAPPING PAYMENT EXCHANGES UNTIL ...
   Payment Handler Continue Process Response([PSn], CS=End)   <- IPB
                   Request any local payment receipt
                   |  Inquire Process State()                 -> IPB
                   |  Inquire Proc. State Resp.(State, [Rcp.])<- IPB
                   Create and transmit Payment Response Block
                   Terminate transaction, actively
                   |  Change Process State(State)             -> IPB
                   |  Change PS Response(State=CompletedOK)   <- IPB
   Consumer        On receipt of final payment scheme data
                   |  Continue Process(PSn)                   -> IPB
                   |  Continue Process Response(CS=End)       <- IPB
                   Check Payment Receipt(Receipt)             -> IPB
                   Check Payment Receipt Response()           <- IPB
                   Request any local payment receipt
                   |  Inquire Process State()                 -> IPB
                   |  Inquire Proc. State Resp.(State, [Rcp.])<- IPB
                   Terminate transaction, actively
                   |  Change Process State(State)             -> IPB
                   |  Change PS Response(State=CompletedOk)   <- IPB
   *+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*
                  Figure 5. Example Payment Message Flows
   1. After Brand Selection and receipt of the IOTP Offer Response
      Block, the Consumer switches from communicating with the Merchant
      to communicating with the Payment Handler.
      This might be a milestone requiring the renewed Consumer's
      agreement about the payment transaction's continuation.
      Particularly, this is a good moment for payment suspension (and
      even cancellation), which will be most probably supported by all
      payment schemes.  Simply, because the actual payment legacy
      systems have not yet been involved in the current transaction.
      Such an agreement might be explicit per transaction or automatic
      based on configured preferences, e.g., early acknowledgments for
      specific payment limits.
      It is assumed, that the transaction proceeds with minimal user
      (Consumer and Payment Handler) interaction and that its progress
      is controlled by the IOTP Application Core and IOTP Payment
      Bridge.
   2. In order to open the actual payment transaction, the IOTP
      Application Core issues the "Start Payment Consumer" request
      towards the IOTP Payment Bridge.  This request carries the whole
      initialization data of the payment transaction being referred to
      by the IOTP Payment Bridge for subsequent consistency checks:
      o  payment brand and its description from the selected Brand
         Element of the IOTP Brand List Component,
      o  payment instrument from preceding inquiry step,
      o  further payment parameters (currency, amount, direction,
         expiration) from the selected Currency Amount element, Brand
         List Component, and Payment Component of the IOTP Offer
         Response Block,
      o  payment protocol from the selected IOTP Pay Protocol Element,
      o  order details contained in the IOTP Order Component which might
         be payment scheme specific,
      o  payment scheme specific data inclusive of the payment protocol
         descriptions from the IOTP Protocol Amount Element, and IOTP
         Pay Protocol Element, and
      o  payment scheme specific data inclusive of the payment protocol
         descriptions, in which the name attribute includes the prefix
         as "Payment:" from the Trading Role Data Component.
      Generally, the called API function re-does most checks of the
      "Check Payment Possibility" call due to lack of strong
      dependencies between both requests: There might be a significant
      delay between both API requests.
      The called API function may return further payment scheme specific
      data being considered as payment specific initialization data for
      the Payment Handler's IOTP Payment Bridge.
      If the fixed Existing Payment Software implements payment
      instrument selection on its own, it may request the Consumer's
      choice at this step.
      The IOTP Payment Bridge reports lack of capability quite similarly
      to the "Check Payment Possibility" request to the IOTP Application
      Core.  The Consumer may decide to resolve the problem, to suspend,
      or to cancel the transaction, but this function call must succeed
      in order to proceed with the transaction.
      Developers of payment modules may decide to omit payment
      instrument related checks like expiration date or refunds
      sufficiency, if such checks are part of the specific payment
      protocol.
      If the IOTP Payment Bridge requests wallet identifiers or pass
      phrases anywhere during the payment process, they should be
      requested by this API function, too.  It is recommended that the
      IOTP Application Core stores plain text pass phrases only in
      runtime memory.
      Finally, the IOTP Application Core generates the IOTP Payment
      Request Block, inserts any returned payment scheme data, and
      submits it to the Payment Handler's system.
   3. The Payment Handler's IOTP Application Core opens the payment
      transaction calling the "Start Payment Payment Handler" API
      function.  The payment brand, its description, payment protocol,
      payment specific data, payment direction, currency and payment
      amount are determined quite similar to the Consumer's IOTP
      Application Core.  Furthermore, the content of the IOTP Payment
      Scheme Component and the IOTP Brand Selection Info Elements are
      passed to this function.
      On success, the Payment Handler's IOTP Payment Bridge responds
      with payment scheme specific data.  On failures, this non-
      interactive server application has to resolve any problems on its
      own or to give up aborting the payment transaction.  However, the
      Consumer may restart the whole payment transaction.  Anyway, the
      payment log file should reflect any trials of payments.
      Eventually, the Payment Handler informs the Consumer about the
      current IOTP Process State using the IOTP Payment Response or IOTP
      Error Block.
      Note that the "Start Payment Payment Handler" call might return
      the Continuation Status "End" such that payment processing
      proceeds with Step 7.
   4. The IOTP Application Core verifies the presence of the Payment
      Exchange Block in the IOTP message and passes the contained
      payment scheme specific data to the fixed IOTP Payment Bridge
      ("Continue Process") which returns the next IOTP Payment Scheme
      Component.
      This Payment Scheme Component is encapsulated in an IOTP Payment
      Exchange Block and transmitted to the Payment Handler.
   5. The Payment Handler's IOTP Application Core verifies the presence
      of the Payment Exchange Block and passes the contained payment
      scheme specific data to the fixed IOTP Payment Bridge ("Continue
      Process") which returns the next IOTP Payment Scheme Component for
      encapsulation and transmission to the Consumer.
   6. The payment process continues with IOTP Payment Exchange Block
      exchanges, carrying the payment scheme specific data.  Each party
      (1) submits the embedded payment scheme specific data
      transparently to the appropriate IOTP Payment Bridge calling the
      "Continue Process" API function, (2) wraps the returned payment
      scheme specific data into an IOTP Payment Exchange Block, and (3)
      transmits this block to the counter party.
      However, the processing of the payment scheme specific data may
      fail for several reasons.  These are signaled by specific error
      codes which are transformed to IOTP Payment Response Blocks
      (generated by Payment Handler) or IOTP Error Blocks (both parties
      may generate them) and transmitted to the counter party.
   7. Eventually, the Payment Handler's IOTP Payment Bridge recognizes
      the termination of the payment transaction and reports this by the
      continuation status "End" on the output parameter of "Continue
      Process" (or "Start Payment Payment Handler").  Then, the IOTP
      Application Core issues the "Inquire Process State" API call and
      verifies whether an IOTP Payment Receipt Component has been
      returned.  The IOTP Application Core wraps the payment receipt,
      the status response, and the optional payment scheme specific data
      in an IOTP Payment Response Block and transmits this block to the
      Consumer.
      However, any of these API calls may fail or any response might be
      incomplete (e.g., lack of payment receipt).  Then, the Consumer
      has to be notified about the failed processing by an IOTP Error
      Block.
      Finally, the Payment Handler terminates the payment transaction
      with the "Change Process State" API call without awaiting any
      further response from the Consumer.  Further failures are not
      reported to the Consumer.
      Note that it might be possible that the Consumer's IOTP Payment
      Bridge has returned the previous payment scheme specific data with
      the continuation status "End".  Even in the absence of this
      knowledge - this status is not exchanged between the Consumer and
      the Payment Handler - the Payment Handler must not supply any
      further payment scheme specific data.  Such data will be rejected
      by the Consumer's IOTP Payment Bridge.
   8. The Consumer passes the optional payment scheme specific data and
      the payment receipt to the fixed IOTP Payment Bridge by "Continue
      Process" and "Check Payment Receipt" API calls.
      Afterwards, the IOTP Application Core issues the "Inquire Process
      State" API call and verifies whether extensions to the payment
      receipt have been returned.
      Finally, the transaction is terminated by calling the "Change
      Process State" API function which verifies and synchronizes the
      reported payment status with the local one and signals any
      inconsistencies.  Any Inconsistency and returned status text
      should be displayed to the Consumer.
      At this point, the payment transaction has already been closed by
      the Payment Handler.  Therefore, any failure has to be resolved
      locally or out-of-band.

2.5. Payment Inquiry

In Baseline IOTP, Payment inquiries are initiated by the Consumer in order to verify the current payment progress and process state at the remote Payment Handler. In the figure 6, PS1 and PS2 indicate the first and second PayScheme Packaged Content data, and [ ] indicates optional.
   *+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*
   Consumer        Start Payment Inquiry()                    -> IPB
                   Start Payment Inquiry Response([PS1])      <- IPB
                   Create and transmit Inquiry Request Trading Block
   Payment Handler Inquire Payment Status([PS1])              -> IPB
                   Inquire Payment Status Res.(State, [PS2])  -> IPB
                   Create and transmit Inquiry Response Trading
                     Block
   Consumer        If Payment Scheme Data present
                   |  Continue Process(PS2)                   -> IPB
                   |  Continue Process Response(CS=End)       <- IPB
                   Change Process State(State)                -> IPB
                   Change Process State Response(State)       <- IPB
   *+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*
                  Figure 6. Remote Process State Inquiry
   1. The Consumer might initiate a payment inquiry once the payment
      transaction has been opened by the IOTP Application Core, i.e., at
      any time after the initial submission of the IOTP Payment Request
      Block.  The IOTP Application Core requests any additional specific
      payment scheme data from the IOTP Payment Bridge which has been
      fixed during brand selection (cf. Section 2.3) using the "Start
      Payment Inquiry" API request.
      Erroneous API responses should be reported to the Consumer and
      valid alternatives (typically retry and cancellation) should be
      presented by the IOTP Application Core.
      This request might perform the complete initialization, e.g.,
      availability check of periphery or pass phrase supplement, and the
      IOTP Payment Bridge reports lack of capability quite similarly to
      the "Check Payment Possibility" request to the IOTP Application
      Core.
      If the IOTP Payment Bridge requests wallet identifiers or pass
      phrases anywhere during the payment process, they should be
      requested by this API function, too.  It is recommended that the
      IOTP Application Core store plain text pass phrases only in
      runtime memory.
      The IOTP Application Core encapsulates any Payment Scheme
      Component in an IOTP Inquiry Request Block and submits the block
      to the Payment Handler.
   2. The Payment Handler analyses the IOTP Inquire Request Block, maps
      the Transaction Identifier to payment related attributes (brand,
      consumer and payment identifiers), determines the appropriate IOTP
      Payment Bridge, and forwards the request to the this IOTP Payment
      Bridge ("Inquire Payment Status").  The IOTP Application Core
      transforms the response to an IOTP Inquiry Response Block and
      transmits it to the Consumer.
   3. On receipt of the respective IOTP Inquiry Response Block the
      Consumer's IOTP Application Core submits any encapsulated payment
      scheme specific data to the IOTP Payment Bridge for verification
      ("Continue Process").
   4. The IOTP Application Core passes the reported payment status
      (except textual descriptions) to the IOTP Payment Bridge ("Change
      Process State") for verification purposes and payment status
      change.  The IOTP Payment Bridge reports any inconsistencies as
      well as the final payment status to the IOTP Application Core.
      Any additional information that might be of interest to the
      Consumer has to be displayed by the IOTP Payment Bridge or
      Existing Payment Software on their own.

2.6. Abnormal Transaction Processing

2.6.1. Failures and Cancellations

The IOTP specification distinguishes between several classes of failures:
      o  Business and technical errors
      o  Error depths of transport, message and block level
      o  Transient errors, warnings, and hard errors.

Any IOTP Payment API has to deal with the receipt of failure notifications by and failure responses. This proposal has borrowed the basic mechanisms for error reporting between the IOTP Application Core and the IOTP Payment Bridge from the actual protocol: Business errors are reported by Status Components within IOTP Response Blocks while technical errors are signaled by Error Components within IOTP Error Blocks.

Cancellations are mimicked as specific business errors which might be initiated by each trading party.

Preferring slim interfaces, this IOTP Payment API introduces one additional Error Code value for business error indication - errors can be raised on every API call. On receipt of this value, the IOTP Application Core has to infer further details by the issuance of the API function call "Inquire Process State".

   *+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*
   Any Party       Issue some API request                     -> IPB
                   Error Response(Error Code)                 <- IPB
                   On "Business Error" response
                   |  Inquire Process State()                 -> IPB
                   |  Inquire P.S. Resp.(State, Receipt)      <- IPB
                   Analyze local process state and try to resolve
                      with optional user interaction
                   If Process State Change needed
                   |  Change Process State (State)            -> IPB
                   |  Change Process State Response(State)    <- IPB
                   If counter party's notification required
                   |  Create Error or Cancel Block (, add to next
                   |  message, ) and transmit it to counter party
   *+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*
                    Figure 7.  Error Response from IPB

The specific Completion Codes "ConsCancelled", "MerchCancelled", and "PaymCancelled" - returned by "Inquire Process State" - determine that the IOTP Cancel Block has to be created instead of an IOTP Error Block.

The rules for determining the required behavior of the IOTP Application Core are given in the IOTP specification.

Note that any payment (intermediate) termination, i.e., failures, cancellations, and even successes are always reported to the IOTP Payment Bridge by the API function "Change Process State". This API function does both status changes and consistency checking / synchronization. Any suspicion of inconsistency should be reported by the IOTP Payment Bridge for display by the IOTP Application Core.

   *+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*
   Any Party       Error Block or Cancel Block Received
                   If Change Process State required
                   |  Change Process State (State)            -> IPB
                   |  Change Process State Response(State)    <- IPB
   *+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*
             Figure 8.  Error Notification from counter party

Not every failure might be visible at the IOTP layer, e.g., the processing of payment transactions might temporarily be hampered by intermediate failures at the payment scheme or protocol transport layer which might be resolved by the actual components.

However, final failures or cancellations have to be reported at the IOTP layer. E.g., communication time-outs and heavily faulty communication channels may disable the transaction.

Any system component may implement time-out recognition and use the aforementioned API mechanisms for the notification of process state changes. But, time-outs may happens while communicating with both the counter party and local system components, like chip card readers or IOTP Payment Bridges. Anyway, the Consumer's IOTP Application Core should notify the Consumer about the resolution alternatives, i.e., retry, suspension, and cancellation.

2.6.2. Resumption

Payment transaction resumption may apply at different steps of a payment transaction:
   o  The Consumer's and Payment Handler's view of the transaction might
      not be synchronized: Due to different time-out values the payment
      transaction may not have been suspended by the counter party.
      Any "Resume Payment ..." API function responds with an Error Code
      on non-suspended payment transaction that signals a business
      error.  Afterwards the IOTP Application Core has to issue the
      "Inquire Process State" API call for further analysis of the
      process state.
   o  One IOTP message sent by one party might not be processed
      successfully or even received by the counter party.  This needs to
      be handled by the actual payment scheme.  It is expected that the
      IOTP Application Core will not recognize anything.
   o  IOTP does not provide any specific signal for payment resumption.
      On receipt of every IOTP Payment Exchange Block, the IOTP
      Application Core has to decide whether this Block belongs to a
      pending transaction or to a suspended transaction that should be
      resumed.  The IOTP Application Core might call the "Inquire
      Process State" API function to update any lack of knowledge.
      Any "Resume Payment" API function responds with an Error Code on
      non-suspended payment transaction that signals a business error.
      Similar, the "Continue Process" API function should report
      business errors on non-pending payment transactions.
   o  The payment transaction may not have been created at the Payment
      Handler (early suspension and failed data transmission).  In that
      case, the IOTP Application Core should respond with a business
      error that signals the repetition of the payment transaction (by
      the Consumer).
      Any "Resume Payment", "Continue Process" or "Inquire Process
      State" API function should return with an Error Code
      "AttValIllegal" on non-existent payment transaction whereby the
      further Error Attribute "Names" denote the payment identifier.
   o  The IOTP Application Core should always request fresh payment
      scheme specific data on resumption - for synchronization purposes
      with the Existing Payment Software.  Old data in the cache that
      has not been sent to the counter party should not be accessed.

If the Consumer does not reconnect within an acceptable amount of time, the Payment Handler's system may perform local failure resolution in order to close the transaction and to retain resources for other transactions ("Change Process State"). If the Consumer reconnect afterwards, an IOTP Payment Response or IOTP Error Block could be generated.

2.7. IOTP Wallet Initialization

At startup or on explicit user request the IOTP Application Core should check its IOTP Payment Bridges' internal status by searching for pending payment transactions.
   1. The IOTP Application Core interrogates the registered IOTP Payment
      Bridges about pending payment transactions.  The IOTP Application
      Core may store indicators for pending transactions and use them
      for driving any subsequent inquiry ("Inquire Pending Payment").
   2. If one or more IOTP Payment Bridges report the presence of pending
      transactions, the IOTP Application Core may try to suspend
      ("Change Process State") or resume (only Consumer: "Resume Payment
      Consumer") the pending transactions (on user request).

The IOTP Payment Bridge may deny the processing of any new payment transactions until the pending transactions have been processed. Such denials are signaled by the error code "Business Error".

2.8. Payment Software Management

The IOTP Application Core provides only a simple and generic interface for the registration of new payment methods / instruments ("Manage Payment Software"). It receives the initial user request and defers the actual registration to the corresponding IOTP Payment Bridge.

The IOTP Application Core may also activate the Existing Payment Software for further payment instrument and wallet administration.

3. Mutuality

The Payment API is formalized using the eXtensible Markup Language (XML). It defines wrapper elements for both the input parameters and the API function's response. In particular, the response wrapper provides common locations for Error Codes and Error Descriptions.

It is anticipated that this description reflects the logical structure of the API parameter and might be used to derive implementation language specific API definitions.

XML definition:

   <!ELEMENT IotpPaymentApiRequest (
     FindAcceptedPaymentBrand |
     FindAcceptedPaymentProtocol |
     GetPaymentInitializationData |
     FindPaymentInstrument |
     CheckPaymentPossiblity |
     StartPaymentConsumer |
     StartPaymentPaymentHandler |
     ResumePaymentConsumer |
     ResumePaymentPaymentHandler |
     ContinueProcess |
     InquireProcessState |
     ChangeProcessState |
     InquireAuthChallenge |
     Authenticate |
     CheckAuthResponse |
     CheckPaymentReceipt |
     ExpandPaymentReceipt |
     RemovePaymentLog |
     PaymentInstrumentInquiry |
     InquirePendingPayment |
     ManagePaymentSoftware |
     StartPaymentInquiry |
     InquirePaymentStatus |
     CallBack )>
   <!ATTLIST IotpPaymentApi
     xml:lang          NMTOKEN   #IMPLIED
     ContentSoftwareID CDATA     #IMPLIED
     xmlns             CDATA     #FIXED
                    "http://www.iotp.org/2000/08/PaymentAPI" >
   <!ELEMENT IotpPaymentApiResponse (ErrorResponse?, (
     FindAcceptedPaymentBrandResponse |
     FindAcceptedPaymentProtocolResponse |
     GetPaymentInitializationDataResponse |
     FindPaymentInstrumentResponse |
     CheckPaymentPossiblityResponse |
     StartPaymentConsumerResponse |
     StartPaymentPaymentHandlerResponse |
     ResumePaymentConsumerResponse |
     ResumePaymentPaymentHandlerResponse |
     ContinueProcessResponse |
     InquireProcessStateResponse |
     ChangeProcessStateResponse |
     InquireAuthChallengeResponse |
     AuthenticateResponse |
     CheckAuthResponseResponse |
     CheckPaymentReceiptResponse |
     ExpandPaymentReceiptResponse |
     RemovePaymentLogResponse |
     PaymentInstrumentInquiryResponse |
     InquirePendingPaymentResponse |
     ManagePaymentSoftwareResponse |
     StartPaymentInquiryResponse |
     InquirePaymentStatusResponse |
     CallBackResponse )?)>
   <!ATTLIST IotpPaymentApiResponse
     xml:lang          NMTOKEN #IMPLIED
     ContentSoftwareID CDATA   #IMPLIED
     xmlns             CDATA   #FIXED
                "http://www.iotp.org/2000/08/PaymentAPI" >
   <!ELEMENT ErrorResponse (ErrorLocation+,PaySchemePackagedContent*) >
   <!ATTLIST ErrorResponse
     xml:lang      NMTOKEN   #IMPLIED
     ErrorCode     NMTOKEN   #REQUIRED
     ErrorDesc     CDATA     #REQUIRED
     Severity(Warning |
       TransientError |
              HardError)     #REQUIRED
     MinRetrySecs  CDATA     #IMPLIED
     SwVendorErrorRef CDATA  #IMPLIED >

Most of the attribute items are intended for immediate insertion in the IOTP Error Block. The attribute values of the Error Location elements attribute have to enriched and transformed into Error Location Elements of the Error Component (cf. IOTP Specification).

Attributes (cf. IOTP Specification):

   xml:lang           Defines the language used by attributes or
                      child elements within this component, unless
                      overridden by an xml:lang attribute on a child
                      element.
   ContentSoftwareId  Contains information which identifies the
                      software that generated the content of the
                      element.  Its purpose is to help resolve
                      interoperability problems that might occur as
                      a result of incompatibilities between messages
                      produced by different software.  It is a single
                      text string in the language defined by
                      "xml:lang".  It must contain, as a minimum
                      problems that might occur as a result of
                      o  the name of the software manufacturer,
                      o  the name of the software,
                      o  the version of the software, and
                      o  the build of the software.
   ErrorCode          Contains an error code which indicates the
                      nature of the error in the message in error.
                      Valid values for the Error Code are given in
                      the following section.  This mnemonic enables
                      the automatic failure resolution of the IOTP
                      Application Core which analyzes the error code
                      value in order to determine the continuation
                      alternatives.
   ErrorDesc          Contains a description of the error in the
                      language defined by xml:lang.  The content of
                      this attribute is defined by the
                      vendor/developer of the software that
                      generated the Error Response Element.
                      It is intended for user display and provides
                      detailed explanations about the failure and
                      its (out-of-band) resolution alternatives.
   Severity           Indicates the severity of the error.  Valid
                      values are:
                      o  Warning.  This indicates that although there
                         is a message in error the IOTP Transaction
                         can still continue.
                      o  TransientError.  This indicates that the
                         error in the message in error may be
                         recovered if the message in error that is
                         referred to by the "Names" attribute is
                         resent.
                      o  HardError.  This indicates that there is an
                         unrecoverable error in the message in error
                         and the IOTP Transaction must stop.
   MinRetrySecs       This attribute should be present if "Severity"
                      is set to "TransientError".  It is the minimum
                      number of whole seconds which the IOTP aware
                      application which received the message
                      reporting the error should wait before
                      resending the message in error identified by
                      the "ErrorLocation" attribute.
                      If Severity is not set to
                      "TransientError" then the value of this
                      attribute is ignored.
   SwVendorErrorRef   This attribute is a reference whose value is
                      set by the vendor/developer of the software
                      that generated the Error Element.  It should
                      contain data that enables the vendor to
                      identify the precise location in their
                      software and the set of circumstances that
                      caused the software to generate a message
                      reporting the error.
Content:
   ErrorLocation      This identifies, where possible, the
                      element and attribute in the message
                      in error that caused the Error
                      Element to be generated.  If the
                      "Severity" of the error is not
                      "TransientError", more that one
                      "ErrorLocation" may be specified as
                      appropriate depending on the nature
                      of the error and at the discretion of
                      the vendor/developer of the IOTP
                      Payment Bridge.
                      Its definition coincides with the
                      IOTP specification whereby the
                      attributes "IotpMsgRef", "BlkRef" and
                      "CompRef" are left blank,
                      intentionally.
   PaySchemePackagedContent  cf. Table 5

3.1. Error Codes

The following table lists the valid values for the ErrorCode attribute of the Error Response Element. The first sentence of the error description contains the default text that can be used to describe the error when displayed or otherwise reported. Individual implementations may translate this into alternative languages at their discretion. However, not every error code may apply to every API call. An Error Code must not be more than 14 characters long. The Error Codes have been taken from the IOTP Specification and extended by some additional codes which are highlighted by a preceding asterisk.

Generally, if the corrupt values have been user supplied, the IOTP Application Core might prompt for their correction. If the renewal fails or if the IOTP Application Core skips any renewals and some notification has to be send to the counter-party, the error code is encapsulated within an IOTP Error Block.

However, the IOTP server application reports business errors - visible at the IOTP layer - in the Status Component of the respective Response Block.

The IOTP Application Core may add the attributes (and values) within the ErrorLocation elements that are omitted by the IOTP Payment Bridge. The following table mentions any modification from this general processing for particular error values. Furthermore, it contains hints for developers of IOTP Application Core software components about the processing of error codes. Conversely, developers of IOTP Payment Bridges get impressions about the expected behavior of the IOTP Application Core.

The IOTP Payment API assumes that the IOTP Application Core implements the dialog boxes needed for error resolution. But it does not assume, that the IOTP Payment Bridge actually relies on them. Instead, the IOTP Payment Bridge may try resolution on its own, may implement specific dialog boxes, and may signal only final failures.

Note: This abstract document assumes that the API parameters are exchanged XML encoded. Therefore, several error values might disappear in lower level language specific derivations.

   Error Value        Error Description
   -----------        -----------------
   Reserved           Reserved.  This error is reserved by the
                      vendor/developer of the software.  Contact
                      the vendor/developer of the software for
                      more information (see the SoftwareId
                      attribute of the Message Id element in the
                      Transaction Reference Block [IOTP]).
   XmlNotWellFrmd     XML not well formed.  The XML document is not
                      well formed.  See [XML] for the meaning of
                      "well formed".
   XmlNotValid        XML not valid.  The XML document is well
                      formed but the document is not valid.  See
                      [XML] for the meaning of "valid".
                      Specifically:
                      o  the XML document does not comply with the
                         constraints defined in the IOTP document
                         type declaration, and
                      o  the XML document does not comply with the
                         constraints defined in the document type
                         declaration of any additional [XML-NS]
                         that are declared.
                      The Names attribute might refer some
                      attributes and elements of the input
                      parameter list.
   (*)ElNotValid      Element not valid.  Invalid element in terms
                      of prescribed syntactical characteristics.
                      The ElementRef attributes of ErrorLocation
                      elements might refer to the corresponding
                      elements (if they have ID attributes).
                      The IOTP Application Core has to replace the
                      error code with "XmlNotValid" before
                      transmission to the counterparty.
   ElUnexpected       Unexpected element.  Although the XML
                      document is well formed and valid, an
                      element is present that is not expected in
                      the particular context according to the
                      rules and constraints contained in this
                      specification.
                      The ElementRef attributes of ErrorLocation
                      elements might refer to the corresponding
                      elements (if they have ID attributes).
   ElNotSupp          Element not supported.  Although the document
                      is well formed and valid, an element is
                      present that
                      o  is consistent with the rules and
                         constraints contained in this
                         specification, but
                      o  is not supported by the IOTP Aware
                         Application which is processing the IOTP
                         Message.
                      The ElementRef attributes of ErrorLocation
                      elements might refer to the corresponding
                      elements (if they have ID attributes).
   ElMissing          Element missing.  Although the document is
                      well formed and valid, an element is missing
                      that should have been present if the rules
                      and constraints contained in this
                      specification are followed.
                      The ElementRef attributes of ErrorLocation
                      elements might refer to the corresponding
                      elements (if they have ID attributes).
   ElContIllegal      Element content illegal.  Although the
                      document is well formed and valid, the
                      element contains values which do not conform
                      the rules and constraints contained in this
                      specification.
                      The ElementRef attributes of ErrorLocation
                      elements might refer to the corresponding
                      element (if they have ID attributes).
                      The IOTP Application Core has to replace the
                      Error Code with "ElNotSupp" before
                      transmission to the counter party, if the
                      ErrorLocation elements refer to
                      non-PackagedContent element.
   EncapProtErr       Encapsulated protocol error.  Although the
                      document is well formed and valid, the
                      Packaged Content of an element contains data
                      from an encapsulated protocol which contains
                      errors.
                      The ElementRef attributes of ErrorLocation
                      elements might refer to the corresponding
                      element (if they have ID attributes).
   AttUnexpected      Unexpected attribute.  Although the XML
                      document is well formed and valid, the
                      presence of the attribute is not expected in
                      the particular context according to the
                      rules and constraints contained in this
                      specification.
                      The AttName attributes of ErrorLocation
                      elements might refer to the corresponding
                      attribute tags.
   (*)AttNotValid     Attribute not valid.  Invalid attribute value
                      in terms of prescribed syntactical
                      characteristics.
                      The AttName attributes of ErrorLocation
                      elements might refer to the corresponding
                      attribute tags.
                      The IOTP Application Core has to replace the
                      error code with "XmlNotValid" before
                      transmission to the counter party.
   AttNotSupp         Attribute not supported.  Although the XML
                      document is well formed and valid, and the
                      presence of the attribute in an element is
                      consistent with the rules and constraints
                      contained in this specification, it is not
                      supported by the IOTP Aware Application
                      which is processing the IOTP Message.
   AttMissing         Attribute missing.  Although the document is
                      well formed and valid, an attribute is
                      missing that should have been present if the
                      rules and constraints contained in this
                      specification are followed.
                      The AttName attributes of ErrorLocation
                      elements might refer to the corresponding
                      attribute tags.
                      If the attribute is required by the IOTP
                      Document Type Declaration (#REQUIRED) the
                      hints for non-valid attributes should be
                      adopted, otherwise these for illegal
                      attribute values.
   AttValIllegal      Attribute value illegal.  The attribute
                      contains a value which does not conform to
                      the rules and constraints contained in this
                      specification.
                      The AttName attributes of ErrorLocation
                      elements might refer to the corresponding
                      attribute tags - valid values are:
                      BrandId: illegal/unknown Brand Identifier -
                      If the brand is not recognized/known by any
                      IOTP Payment Bridge, the IOTP Application
                      Core may offer the registration of a new
                      Payment Instrument.
                      PaymentInstrumentId: illegal/unknown
                      Payment Instrument Identifier - This
                      indicates a serious communication problem if
                      the attribute value has been reported by the
                      same "wallet" on a previous inquiry
                      requests.  The IOTP Application Core has to
                      replace the error code with
                      "UnknownError" before transmission to the
                      counter party.
                      WalletId: illegal/unknown Wallet Identifier
                      - It is assumed that the wallet identifier
                      is checked before the pass phrase.  On
                      invalid wallet identifiers, the IOTP
                      Application Core may open the dialog in
                      order to request the correct wallet
                      identifier.  In addition, any pass phrase may
                      be supplied by the user.  The dialog should
                      indicate the respective payment brand(s).
                      The IOTP Application Core has to replace the
                      error code with "UnknownError" before
                      transmission to the counter party.
                      Passphrase:   illegal/unknown Pass Phrase -
                      The IOTP Application Core may open the
                      dialog in order to request the correct pass
                      phrase.  If the pass phrase is wallet
                      identifier specific the dialog should
                      display the wallet identifier.  The IOTP
                      Application Core has to replace the error
                      code with "TransportError" before
                      transmission to the counter party.
                      Action:  illegal / unknown / unsupported
                      Action
                      PropertyTypeList:  lists contains illegal /
                      unknown / unsupported Property Types - The
                      IOTP Application Core tries only the local
                      resolution but does never transmit any IOTP
                      Error Block to the counter party.
                      CurrCode: illegal/unknown/unsupported
                      Currency Code
                      CurrCodeType: illegal/unknown/unsupported
                      Currency Code Type
                      Amount: illegal/unknown/unsupported Payment
                      Amount
                      PayDirection: illegal/unknown/unsupported
                      Payment Direction
                      ProtocolId:   illegal/unknown/unsupported
                      Protocol Identifier
                      OkFrom: illegal/unknown/unsupported OkFrom
                      Timestamp
                      OkTo:   illegal/unknown/unsupported OkTo
                      Timestamp
                      ConsumerPayId: illegal/unknown Consumer
                      Payment Identifier
                      PaymentHandlerPayId: illegal/unknown Payment
                      Handler Payment Identifier
                      PayId: illegal/unknown Payment Identifier
   AttValNotRecog     Attribute Value Not Recognized.  The
                      attribute contains a value which the IOTP
                      Aware Application generating the message
                      reporting the error could not recognize.
                      The AttName attributes of ErrorLocation
                      elements might refer to the corresponding
                      attribute tags.
   MsgTooLarge        Message too large.  The message is too large
                      to be processed by the IOTP Payment Bridge
                      (or IOTP Application Core).
   ElTooLarge         Element too large.  The element is too large
                      to be processed by the IOTP Payment Bridge
                      (or IOTP Application Core).
                      The ElementRef attributes of ErrorLocation
                      elements might refer to the corresponding
                      elements.
   ValueTooSmall      Value too small or early.  The value of all
                      or part of an element content or an
                      attribute, although valid, is too small.
                      The ErrorLocation elements might refer to
                      the corresponding attribute tags or
                      elements.
   ValueTooLarge      Value too large or in the future.  The value
                      of all or part of an element content or an
                      attribute, although valid, is too large.
                      The ErrorLocation elements might refer to
                      the corresponding attribute tags or
                      elements.
   ElInconsistent     Element Inconsistent.  Although the document
                      is well formed and valid, according to the
                      rules and constraints contained in this
                      specification:
                      o  the content of an element is inconsistent
                         with the content of other elements or
                         their attributes, or
                      o  the value of an attribute is inconsistent
                         with the value of one or more other
                         attributes.
                      The Error Description may contain further
                      explanations.
                      The ErrorLocation elements might refer to
                      the corresponding attribute tags or elements
                      that are inconsistent.
   TransportError     Transport Error.  This error code is used to
                      indicate that there is a problem with the
                      transport mechanism that is preventing the
                      message from being received.  It is typically
                      associated with a "Transient Error".
                      The connection to some periphery or the
                      counter party could not be established,
                      is erroneous, or has been lost.
                      The Error Description may contain further
                      narrative explanations, e.g., "chip card
                      does not respond", "remote account manager
                      unreachable", "Internet connection to xyz
                      lost", "no Internet connection available",
                      "no modem connected", or "serial port to
                      modem used by another application".  This
                      text should be shown to the end user.  If
                      timeout has occurred at the Consumer this
                      text should be shown and the Consumer may
                      decide how to proceed - alternatives are
                      retry, payment transaction suspension, and
                      cancellation.
   MsgBeingProc       Message Being Processed.  This error code is
                      only used with a Severity of Transient
                      Error.  It indicates that the previous
                      message, which may be an exchange message or
                      a request message, is being processed and,
                      if no response is received by the time
                      indicated by the "MinRetrySecs" attribute,
                      then the original message should be resent.
   SystemBusy         System Busy.  This error code is only used
                      with a Severity of Transient Error.  It
                      indicates that the IOTP Payment Bridge or
                      Existing Payment Software that received the
                      API request is currently too busy to handle
                      it.  If no response is received by the time
                      indicated by the "MinRetrySecs" attribute,
                      then the original message should be resent.
                      The Error Description may provide further
                      explanations, e.g., "wallet / chip card
                      reader is unavailable or locked by another
                      payment transaction", "payment gateway is
                      overloaded", "unknown chip card reader", or
                      "unrecognized chip card inserted, change
                      chip card".
                      The Consumer's IOTP Application Core may
                      display the error description and ask the
                      Consumer about the continuation -
                      alternatives are retry, payment transaction
                      suspension, and cancellation.
   UnknownError       Unknown Error.  Indicates that the
                      transaction cannot complete for some reason
                      that is not covered explicitly by any of the
                      other errors.  The Error description
                      attribute should be used to indicate the
                      nature of the problem.
                      The ErrorLocation elements might refer to
                      the corresponding attribute tags or elements
                      that are inconsistent.
   (*)SyntaxError     Syntax Error.  An (unknown) syntax error has
                      occurred.
                      The ErrorLocation elements might refer to
                      the corresponding attribute tags or elements
                      that are inconsistent.
                      The IOTP Application Core has to replace the
                      error code with "XmlNotValid" or
                      "UnknownError" before transmission to the
                      counter party.
   (*)ReqRefused      Request refused.  The API request is
                      (currently) refused by the IOTP Payment
                      Bridge.  The error description may provide
                      further explanations, e.g., "wallet / chip
                      card reader is unavailable or locked by
                      another payment transaction", "payment
                      gateway is overloaded", "unknown chip card
                      reader", or "unrecognized chip card
                      inserted, change chip card".
                      The Consumer's IOTP Application Core may
                      display the error description and ask the
                      Consumer about the continuation -
                      alternatives are retry, payment transaction
                      suspension, and cancellation.  Denials due to
                      invalid Process States should be signaled by
                      "BusinessError".  Typically, this kind of
                      error is not passed to the counter party's
                      IOTP Application Core.  Otherwise, it maps to
                      "TransportError" or "UnknownError".
   (*)ReqNotSupp      Request not supported.  The API
                      function(ality) has not been implemented in
                      the IOTP Payment Bridge.  Typically, this
                      kind of error is not passed to the
                      counter party's IOTP Application Core.
                      Otherwise, it maps to "TransportError" or
                      "UnknownError".
   (*)BusError        Business Error.  The API request has been
                      rejected because some payment transaction
                      has an illegal payment status.
                      Particularly, this error code is used to
                      signal any raise of payment business layered
                      failures.
                      The ErrorLocation elements may refer to
                      payment transactions using the party's
                      Payment Identifier - it defaults to the
                      current transaction or might contain the
                      current payment transaction party's Payment
                      Identifier - identified by the ElementRef
                      attribute while the AttName attribute is
                      fixed with "PayId".
                      The IOTP Application Core must inquire the
                      IOTP Payment Bridge about the actual Process
                      State which actually encodes the business
                      error ("Inquire Process State").
                      This error code must not be
                      passed to the counter party's IOTP
                      Application Core.
                        Table 2: Common Error Codes

The IOTP Payment Bridge may also use the error description in order to notify the Consumer about further necessary steps for failure resolution, e.g., "Sorry, your payment transaction failed. Unfortunately, you have been charged, please contact your issuer."

3.2. Attributes and Elements

The following table explains the XML attributes in alphabetical order - any parenthesized number after the attribute tag is a recommended maximal length of the attribute value in characters:
   Attribute           Description
   ---------           -----------
   Amount    (11)      Indicates the payment amount to be paid in
   AmountFrom(11)      whole and fractional units of the currency.
   AmountTo  (11)      For example $245.35 would be expressed
                       "245.35".  Note that values smaller than the
                       smallest denomination are allowed.  For
                       example one tenth of a cent would be
                       "0.001".
   AuthenticationId    An identifier specified by the
                       authenticator which, if returned by the
                       organization that receives the
                       authentication request, will enable the
                       authenticator to identify which
                       authentication is being referred to.
   BrandId  (128)      This contains a unique identifier for the
                       brand (or promotional brand).  It is used to
                       match against a list of Payment Instruments
                       which the Consumer holds to determine
                       whether or not the Consumer can pay with the
                       Brand.
                       Values of BrandId are managed under
                       procedure being described in the IOTP
                       protocol specification.
   BrandLogoNetLocn    The net location which can be used to
                       download the logo for the organization (cf.
                       IOTP Specification).
                       The content of this attribute must conform
                       to [URL].
   BrandName           This contains the name of the brand, for
                       example "MasterCard Credit".  This is the
                       description of the Brand which is displayed
                       to the consumer in the Consumer's language
                       defined by "xml:lang".  For example it might
                       be "American Airlines Advantage Visa".  Note
                       that this attribute is not used for matching
                       against the payment instruments held by the
                       Consumer.
   BrandNarrative      This optional attribute is
                       used by the Merchant to indicate some
                       special conditions or benefit which would
                       apply if the Consumer selected that brand.
                       For example "5% discount", "free shipping
                       and handling", "free breakage insurance for
                       1 year", "double air miles apply", etc.
   CallBackFunction    A function which is called whenever there is
                       a change of Process State or payment
                       progress, e.g., for display updates.  However,
                       the IOTP Payment Bridge may use its own
                       mechanisms and dialog boxes.
   CallBackLanguageList
                       A list of language codes which contain, in
                       order of preference, the languages in which
                       the text passed to the Call Back function
                       will be encoded.
   CompletionCode (14) Indicates how the process completed.
                       It is required if ProcessState is set to
                       "Failed" otherwise it is ignored.  Valid
                       values as well as recovery options are given
                       in the IOTP specification.
                       The IOTP Payment Bridge may also use the
                       Status Description to notify the Consumer
                       about further necessary steps in order to
                       resolve some kind of business failures,
                       e.g.,
                       o  "sorry, your payment transaction failed.
                          Unfortunately, you have been charged,
                          please contact your issuer."
                       o  "insufficient capacity left (on your
                          stored value card) for refund",
                       o  "payment failed/chip card error/internal
                          error, please contact your payment
                          instrument's issuer"
   ConsumerDesc        A narrative description of the Consumer.
   ConsumerPayId (14)  An unique identifier specified by the
                       Consumer that, if returned by the Payment
                       Handler in another Payment Scheme Component
                       or by other means, enables the Consumer to
                       identify which payment is being referred to.
                       This unique identifier is generated by the
                       IOTP Application Core and submitted to the
                       IOTP Payment Bridge on every API call.  It
                       may equal the Payment Handler Payment
                       Identifiers but need not necessarily be so.
                       The uniqueness extends to multiple payment
                       instruments, payment brands, payment
                       protocols, wallet identifiers, and even
                       multiple IOTP Payment Bridges.
   ContStatus          During payment progress, this status value
                       indicates whether the payment needs to be
                       continued with further IOTP Payment Scheme
                       Component exchanges with the remote party.
                       "End" indicates that the reported payment
                       scheme data is the last data to be exchanged
                       with the counter party.
   ContentSoftwareId   This contains information that identifies
                       the software that generated the content of
                       the element.  Its purpose is to help resolve
                       interoperability problems that might occur
                       as a result of incompatibilities between
                       messages produced by different software.  It
                       is a single text string in the language
                       defined by xml:lang.  It must contain, as a
                       minimum:
                       o  the name of the software manufacturer,
                       o  the name of the software,
                       o  the version of the software, and
                       o  the build of the software.
   CurrCodeType (14)   Indicates the domain of the CurrCode.  This
                       attribute is included so that the currency
                       code may support nonstandard currencies
                       such as frequent flyer point, trading
                       stamps, etc.  Its values may be
                       o  ISO-4217-A, the default, indicates the
                          currency code is the three-letter
                          alphabetic code that conform to ISO-4217
                          [ISO4217].
                       o  IOTP indicates that the values of
                          CurrCode are managed under the procedure
                          described in [IOTP].
   CurrCode  (14)      A code which identifies the currency to be
                       used in the payment.  The domain of valid
                       currency codes is defined by "CurrCodeType"
   MerchantPayId  (14) An private identifier specified by the
                       Merchant which will enable the Merchant to
                       identify which payment is being referred to.
                       It is a pure private item and is never sent
                       to any other party.  It is provided by the
                       IOTP Payment Bridge on payment preparation
                       during brand compilation.
Cf. To "ConsumerPayId" for note about uniqueness.
   MerchantOrgId  (64) A local item that might refer to some
                       specific shop in a multi shop environment.
                       This item is optional and might enrich the
                       Wallet Identifier which itself can be used
                       for the same purpose.
   Name                Distinguishes between multiple occurrences
                       of Packaged Content Elements at the same
                       point in IOTP.  For example:
                       <ABCD>
                         <PackagedContent Name='FirstPiece'>
                           snroasdfnas934k
                         </PackagedContent>
                         <PackagedContent Name='SecondPiece'>
                           dvdsjnl5poidsdsflkjnw45
                         </PackagedContent>
                       </ABCD>
                       The "Name" attribute may be omitted, for
                       example if there is only one Packaged
                       Content element.
   OkFrom  (30)        The date and time in UTC Format range
   OkTo  (30)          indicated by the merchant in which the
                       Payment Handler may accept the payment.
                       For more information, see [UTC].
   Passphrase  (32)    Payment wallets may use pass phrase
                       protection for transaction data and payment
                       instruments' data.  However, it is assumed
                       that there exists a public and customizable
                       payment instrument identifier such that
                       these identifiers together with their
                       relationship to payment brands, payment
                       protocols, payment directions, and currency
                       amounts can be queried by the IOTP
                       application without any pass phrase
                       knowledge.
   PayDirection        Indicates the direction in which the
                       payment for which a Brand is being selected
                       is to be made.  Its values may be:
                       o  Debit: The sender of the Payment Request
                          Block (e.g., the Consumer) to which this
                          Brand List relates will make the payment
                          to the Payment Handler, or
                       o  Credit: The sender of the Payment Request
                          Block to which this Brand List relates
                          will receive a payment from the Payment
                          Handler.
   PayId (14)          This attribute is introduced for API
                       simplification:
                       o  The Consumer has to identify PayId and
                          ConsumerPayId.
                       o  The Merchant has to identify PayId and
                          MerchantPayId.
                       o  The Payment Handler has to identify PayId
                          and Payment Handler Pay Id.
   PayInstId           This contains the unique identifier used
                       internally by the IOTP Payment
                       Bridge/Existing Payment Software.
   PayInstName         This contains the user-defined name of the
                       payment instrument.  There exist no
                       (technical) constraints like uniqueness.  The
                       "xml:lang" attribute denotes the language
                       encoding of its value.
   PaymentHandlerDesc  A narrative description of the Payment
                       Handler.
   PaymentHandlerPayId An unique identifier specified by the
     (14)              Payment Handler that, if returned by the
                       Consumer in another Payment Scheme Component
                       or by other means, enables the Payment
                       Handler to identify which payment is being
                       referred to.  It is required whenever it is
                       known.
Cf. To "ConsumerPayId" for note about uniqueness.
   PaymentInstrumentId An identifier for a specific payment
     (32)              instrument, e.g., "credit card", "Mondex card
                       for English Pounds".  This identifier is
                       fully customizable.  It is assumed, that it
                       does not contain confidential information or
                       even an indication of it.  The payment
                       instrument identifier is unique within each
                       payment brand.  It is displayed to the
                       Consumer during brand selection.
   PayReceiptNameRefs  Optionally contains element references to
     (32)              other elements (containing payment scheme
                       specific data) that together make up the
                       receipt.  Note that each payment scheme
                       defines in its supplement the elements that
                       must be referenced
                       The IOTP Application Core should save all
                       the components referenced so that the
                       payment receipt can be reconstructed when
                       required.
   PayReqNetLocn       The Net Location indicating where an
                       unsecured Payment Request message should be
                       sent if this protocol choice is used.
                       The content of this attribute must conform
                       to [URL] and depends on the Transport
                       Mechanism.
   PercentComplete (3) A number between 0 and 100 which indicates
                       the progress of the payment transaction.  The
                       values range between 0 and 99 for pending
                       and suspended transactions.
   ProcessState        Contains a Process State Code that
                       indicates the current state of the process
                       being carried out.  Valid values are:
                       o  NotYetStarted.  The Payment Request Block
                          has been received but processing of the
                          Payment Request has not yet started
                       o  InProgress.  The payment transaction is
                          pending.  The processing of the (Payment)
                          Request Block has started but it is not
                          yet complete.
                       o  (*)Suspended: The payment transaction has
                          been suspended and can be resumed.
                       This process state is mapped to
                       "InProgress", if it is passed to the
                       counter party's IOTP Application Core.
                       o  CompletedOk.  The processing of the (Payment)
                          Request Block and any following Payment
                          Exchange Blocks has completed successfully.
                       o  Failed.  The payment processing has finally
                          failed for a Business Error.
                       o  ProcessError.  This value is only used
                          when the Status Component is being used in
                          connection with an Inquiry Request Trading
                          Block.  It indicates there was a Technical
                          Error in the Request Block which is being
                          processed or some internal processing
                          error.  Each party's IOTP Payment Bridge
                          uses this value in order to notify the
                          IOTP Application Core about the presence
                          of technical errors.
   PropertyType  (14)  The property type defines codes used for
                       interrogation of specific properties about a
                       payment instrument.  They are unique for each
                       payment brand.  The predefined property "all"
                       is used on general inquiries.  However, these
                       property types are not used during normal
                       payment processing.  E.g., they may apply to
                       payment brand specific transactions or
                       out-of-band failure resolution.
   PropertyDesc        The property description carries the
                       respective human readable property (value)'s
                       description.
   PropertyValue       The actual property value intends automatic
                       post processing.
   ProtocolBrandId (64)This is an identifier to be used with a
                       particular payment protocol.  For example,
                       SET and EMV have their own well defined, yet
                       different, values for the Brand identifier
                       to be used with each protocol.  The valid values
                       of this attribute are defined in the
                       supplement for the payment protocol
                       identified by "ProtocolId" that describes
                       how the payment protocol works with IOTP.
                       Identifier maps to at most one Protocol
                       Brand Identifier.
   ProtocolId  (64)    An identifier for a specific payment
                       protocol and version, e.g., "SETv1.0",
                       "ecash".  Valid values are defined by
                       supplements to the IOTP specification and
                       they are unique within each payment brand.
   ProtocolIds         A sequence of Protocol Identifiers
   ProtocolName        A narrative description of the payment
                       protocol and its version in the language
                       identified by "xml:lang".  For example
                       "Secure Electronic Transaction Version 1.0".
                       Its purpose is to help provide information
                       on the payment protocol being used if
                       problems arise.
   SecPayReqNetLocn    The Net Location indicating where a secured
                       Payment Request message should be sent if
                       this protocol choice is used.
                       A secured payment involves the use of a
                       secure channel such as [TLS] in order
                       to communicate with the Payment Handler.
                       The content of this attribute must conform
                       to [URL].
   ReceiverOrgId       The Organization Identification which
                       receives the payment bridge processing
                       Trading Role Data PackagedContent.
   StatusDesc  (256)   An optional textual description of the
                       current process state in the language
                       identified by "xml:lang" that should be
                       displayed to the Consumer.  The usage of this
                       attribute is defined in the payment
                       supplement for the payment method being
                       used.  Particularly, it provides hints for
                       out-of-band failure resolution.  Its length
                       is limited to 256 characters.
   StyleSheetNetLocn   This contains the net location to a style
                       sheet with visualisation rules for XML
                       encoded data.
   TimeStamp  (30)     The date and time in UTC Format when the
                       payment transaction has been started.
                       For more information on UTC, see [UTC].
   WalletId  (32)      Many existing payment wallet software are
                       multiple wallet capable.  The Wallet
                       Identifier selects the actual wallet.  It is
                       assumed, that the wallet identifier is a
                       public item, that might be stored by the
                       IOTP Application Core.
   xml:lang            Defines the language used by the Process
                       State Description attribute (cf. IOTP
                       Specification)
                            Table 3: Attributes

The following table explains the XML elements in alphabetical order:

   Element             Description
   -------             -----------
   Algorithm           This contains information which describes
                       an Algorithm that may be used to generate
                       the Authentication response.
                       The algorithm that may be used is
                       identified by the Name attribute (cf. IOTP
                       Specification).
   AuthReqPackagedContent   The Authentication Request Packaged
                       Content originates from a Authentication
                       (Data/Response) Component's content
                       whereby the outermost element tags are
                       prefixed with "AuthReq".  Its declaration
                       coincides with the Packaged Content's
                       declaration (cf. IOTP Specification).  It
                       encapsulates the authentication challenge
                       value.  The content of this information is
                       defined in the supplement for a payment
                       protocol.
   AuthResPackagedContent   The Authentication Response Packaged
                       Content originates from a Authentication
                       Response Component's content whereby the
                       outermost element tags are prefixed with
                       "AuthRes".
                       Its declaration coincides with the
                       Packaged Content's declaration (cf. IOTP
                       Specification).  It encapsulates the
                       authentication response value.  The
                       content of this information is defined in
                       the supplement for a payment protocol.
   BrandPackagedContent     Container for further payment brand
                       description.  Its content originates from
                       a Brand Element content whose outermost
                       element tags are prefixed with "Brand".
                       Its declaration coincides with the
                       Packaged Content's declaration (cf. IOTP
                       Specification).
   BrandSelBrandInfoPackagedContent
                       This contains any additional data that
                       may be required by a particular payment
                       brand.  It forms the content of the Brand
                       Selection Brand Info Element.
   BrandSelProtocolAmountInfoPackagedContent
                       This contains any additional data that
                       may be required by a particular payment
                       brand in the format.  It forms the content
                       of the Brand Selection Protocol Amount
                       Info Element.
   BrandSelCurrencyAmountInfoPackagedContent
                       This contains any additional data that is
                       payment brand and currency specific in
                       the format.  It forms the content of the
                       Brand Selection Currency Amount Info
                       Element.
   MerchantData        Any merchant related data that might be
                       used by the IOTP Payment Bridge for
                       different purposes, e.g., it might
                       contain IDs to access some mall data,
                       but not cryptographic keys.  Its Packaged
                       declaration coincides with the Content's
                       declaration (cf. IOTP Specification).
   PackagedContent     Generic Container for non-IOTP data (cf.
                       IOTP Specification).
   PayProtocolPackagedContent
                       The Pay Protocol Packaged Content
                       originates from a Pay Protocol
                       Element's content whereby the outermost
                       element tags are prefixed with
                       "PayProtocol".  It contains information
                       about the protocol which is used by
                       the payment protocol.  The content of
                       this information is defined in the
                       supplement for a payment protocol.  Its
                       declaration coincides with the Packaged
                       Content's declaration (cf. IOTP
                       Specification).
   PaySchemePackagedContent
                       The PayScheme Packaged Content originates
                       from a Payment Scheme Component's content
                       whereby the outermost element tags are
                       prefixed with "PayScheme".  Its
                       declaration coincides with the Packaged
                       Content's declaration (cf. IOTP
                       Specification).  It carries the payment
                       specific data.  The content of this
                       information is defined in the supplement
                       for a payment protocol.
   ProtocolAmountPackagedContent
                       The Protocol Amount Packaged Content
                       originates from a Protocol Amount
                       Element's content whereby the outermost
                       element tags are prefixed with "Amount".
                       Its declaration coincides with the
                       Packaged Content's declaration (cf. IOTP
                       Specification).  It contains information
                       about the protocol which is used by the
                       payment protocol.  The content of this
                       information is defined in the supplement
                       for a payment protocol.
   ProtocolBrandPackagedContent
                       The Protocol Brand Packaged Content
                       originates from a Protocol Brand
                       Element's content whereby the outermost
                       element tags are prefixed with
                       "ProtocolBrand".  Its declaration
                       coincides with the Packaged Content's
                       declaration (cf. IOTP Specification).  It
                       contains information about the brand
                       which might be used by the payment
                       protocol.  The content of this information
                       is defined in the supplement for a
                       payment protocol.
   ResponsePackagedContent
                       Container for authentication response
                       data.  Its content originates from a
                       Authentication Response Component's
                       Packaged Content whose outermost element
                       tags are prefixed with "Response".  Its
                       declaration coincides with the Packaged
                       Content's declaration (cf. IOTP
                       Specification).
   TradingRoleDataPackagedContent
                       The TradingRoleData Packaged Content
                       originates from a TradingRoleData
                       Component's content whereby the outermost
                       element tags are prefixed with
                       "TradingRoleData".  Its declaration
                       coincides with the Packaged Content's
                       declaration (cf. IOTP Specification).  It
                       contains information from Merchant to
                       Payment Handler via Consumer about the
                       protocol which is used by the payment.
                       The content of this information is
                       defined in the supplement for a payment
                       protocol.  The Name attribute in this
                       packaged contents must include prefix as
                       "Payment:" to indicate that the payment
                       bridge processes this, for example
                       "Payment:SET-OD".  See [SET/IOTP] for
                       more information.
                       The element's declaration coincides with
                       the Packaged Content's declaration (cf.
                       IOTP Specification).
                             Table 4: Elements

XML definition:

   <!ENTITY % AuthReqPackagedContent       "PackagedContent">
   <!ENTITY % AuthResPackagedContent       "PackagedContent">
   <!ENTITY % BrandPackagedContent         "PackagedContent">
   <!ENTITY % BrandSelInfoPackagedContent  "PackagedContent">
   <!ENTITY % BrandSelProtocolAmountPackagedContent
                                           "PackagedContent">
   <!ENTITY % BrandSelCurrencyAmountPackagedContent
                                           "PackagedContent">
   <!ENTITY % ProtocolAmountPackagedContent
                                           "PackagedContent">
   <!ENTITY % PayProtocolPackagedContent   "PackagedContent">
   <!ENTITY % TradingRoleDataPackagedContent "PackagedContent">
   <!ENTITY % MerchantData "PackagedContent">
   <!ENTITY % PaySchemePackagedContent     "PackagedContent">

3.3. Process States

The IOTP Payment API supports six different attribute values that encode the transaction status from the IOTP's point of view, i.e., the appropriate point of view at the interface between the IOTP Application Core and IOTP Payment Bridge. This point of view does not completely mimic the more detailed view on the actual payment by the actual Existing Payment Software or IOTP Payment Bridge.

The following three tables distinguish between the Merchant's, Consumer's, and Payment Handlers' environment. They extend the aforementioned explanations towards the mapping between IOTP process states and the internal payment scheme related states of the Existing Payment Software/IOTP Payment Bridge.

3.3.1. Merchant

The Merchant's point of view of payment is limited to the local payment initiation being interlaced with order processing because IOTP assigns the actual payment processing to the Payment Handler.
   ProcessState        Description
   ------------        -----------
   NotYetStarted       The Payment Transaction exists within the
                       IOTP Application Core, i.e., the
                       Merchant's shop has already signaled to
                       the IOTP Application Core that an IOTP
                       transaction has been initiated by the
                       Consumer.
                       However, neither any API call has been
                       issued to the IOTP Payment Bridge nor has
                       the IOTP Order Request has been created.
   InProgress          The IOTP Application changes the process
                       state to this value when it issues the
                       first API call to the Payment Bridge
                       during Brand List compilation.
                       This value indicates that the Payment
                       Bridge might have some knowledge about
                       the expected payment or might have
                       performed some preparatory tasks (even
                       with the Payment Handler out-of-band to
                       IOTP).
                       However, this value does not indicate
                       that any IOTP Order Request has been
                       created and transmitted to the Consumer.
   Suspended           The IOTP transaction has been suspended
                       before the order request block has been
                       transmitted to the Consumer.
                       Implicitly, the payment is also deferred.
   CompletedOk         The IOTP Order Request has been
                       successfully created and transmitted to
                       the Consumer.  Actually, this process
                       state indicates only that the order
                       processing has been finished.
                       But it contains no indication about the
                       status of the actual payment, which is
                       accepted by the Payment Handler.
                       However, successful order processing
                       signals the IOTP Application Core that a
                       payment with some specific parameters is
                       expected within the near future.  And this
                       signal might be used by the Existing
                       Payment Software for similar purposes.
                       This attribute might be interpreted as
                       successful preparation of the payment
                       system.
                       Particularly, it is expected that the
                       Existing Payment Software maps this IOTP
                       status value to some other internal
                       value, e.g., "NotYetStarted", that is more
                       accurate from its point of view.
                       As IOTP provides no communication channel
                       between the Merchant and Payment Handler,
                       any change of payment process state will
                       be initiated out-of-band to IOTP, e.g., by
                       electronic statements of account or
                       payment scheme specific mechanisms.
   Failed              The IOTP transaction, i.e., order
                       processing, has failed for some
                       (business) reason and it is known that no
                       payment will occur.
                       This indication might be used to clear
                       all data about this transaction within
                       the Existing Payment Bridge (by
                       "RemovePaymentLog" or
                       "ChangeProcessState") or to reverse any
                       preparation (with the Payment Handler
                       out-of-band to IOTP).
                       However, the ideal point of view of IOTP
                       suspects that the actual payment
                       transaction has been neither started nor
                       initiated.
   ProcessError        The IOTP transaction, i.e., order
                       processing, has failed for some
                       (technical) reason and it is known that
                       no payment will occur.
                       This indication might be used to clear
                       all data about this transaction within
                       the Existing Payment Bridge (by
                       "RemovePaymentLog" or
                       "ChangeProcessState") or to reverse any
                       preparation (with the Payment Handler
                       out-of-band to IOTP).
                       However, the ideal point of view of IOTP
                       suspects that the actual payment
                       transaction has been neither started nor
                       initiated.
                             Table 5: Merchant

3.3.2. Consumer

The Consumer's IOTP Application Core restricts its point of view to the payment transaction. It is assumed that the IOTP Payment Bridge handles the preceding brand selection process in a stateless manner.
   ProcessState        Description
   ------------        -----------
   NotYetStarted       This encodes the initial process state of
                       any IOTP payment transaction.  This value
                       is set during brand selection but it
                       normally will not change during the whole brand
                       selection process.
   InProgress          With the issuance of the Start Payment
                       Consumer API call, the IOTP Application
                       Core changes the process state to this
                       value.
   Suspended           The payment transaction has been
                       suspended.  Suspension may occur anywhere
                       during brand selection (with the
                       Merchant) or payment processing (with the
                       Payment Handler).  On resumption, the IOTP
                       Application Core and the IOTP Payment
                       Bridge have to use other internal data to
                       decide whether brand selection or actual
                       payment processing needs to be continued,
                       i.e., whether the process state needs to
                       be reset to "NotYetStarted" or
                       "InProgress".
                       Note that the Payment API assumes
                       stateless brand selection by the IOTP
                       Payment Bridge.  Typically, any suspension
                       during brand selection requires the
                       repetition of the whole process.  Hereby,
                       the IOTP Application Core might need to
                       consider any already negotiated
                       conditions in a brand depended purchase
                       (brand, protocol).
   CompletedOk         The successful payment has been
                       acknowledged by the Payment Handler, i.e.,
                       the successful IOTP Payment Response has
                       been received.
                       Implicitly, this implies successful order
                       processing.
   Failed              The IOTP transaction, i.e., order or
                       payment processing, has failed for some
                       (business) reason.  In either case it is
                       known that the payment will not succeed.
   ProcessError        The IOTP transaction, i.e., order or
                       payment processing, has failed for some
                       (technical) reason.
                       However, the local process state might be
                       different from that of Payment Handler.
                             Table 6: Consumer

3.3.3. Payment Handler

The Payment Handler is responsible for the actual payment processing. New payment transactions are reported by the Consumer with the transmission of new IOTP Payment Request Blocks. IOTP Payment Exchange Block are send by the Consumer for payment transaction continuation and resumption.
   ProcessState        Description
   ------------        -----------
   NotYetStarted       This encodes the initial process state of
                       any payment transaction.  Typically, this
                       value will last for a short amount of
                       time.
   InProgress          The IOTP Application Core changes the
                       process state changes to "InProgress"
                       when the Payment Handler starts with the
                       actual processing of the IOTP Payment
                       Request Block.
                       Note that this does not assume that the
                       "StartPaymentPaymentHandler" API function
                       has been called.
   Suspended           The payment transaction has been
                       suspended.
   CompletedOk         The payment has been processed,
                       successfully, i.e., the IOTP Payment
                       Response Block was created and
                       transmitted to the Consumer.
   Failed              The payment transaction, has finally
                       failed for some (business) reason.
                       Note that this value encodes the payment
                       state reported by the IOTP Payment Bridge
                       on "InquireProcessState".  It neither
                       reflects whether the payment receipt has
                       been inquired nor whether the IOTP
                       Payment Response Block has been created
                       and submitted to the Consumer.
   ProcessError        The payment transaction, has finally
                       failed for some (technical) reason.
                       Note that this value encodes the payment
                       state reported by the IOTP Payment
                       Bridge.  It does not reflect whether some
                       IOTP Error Block has been created and
                       submitted to the Consumer.
                             Table 7: Consumer

4. Payment API Calls

4.1. Brand Compilation Related API Calls

4.1.1. Find Accepted Payment Brand

This API function determines the payment brands being accepted by the Payment Handler on behalf of the Merchant.
   Input Parameters
   o  Payment Direction - provided by the IOTP Application Core
   o  Currency Code and Currency - provided by the IOTP Application
      Core
   o  Payment Amount - provided by the IOTP Application Core
   o  Merchant Payment Identifier - Merchant's unique private
      reference to the payment transaction
   o  Merchant Organisation Identifier - used for distinction between
      multiple merchants that share the some IOTP merchant system
   o  Wallet Identifier - managed by the IOTP Application Core
   o  Merchant Data - specific data used by the IOTP Payment Bridge
      which is managed in the IOTP Application Core.
XML definition:
   <!ELEMENT FindAcceptedPaymentBrand (MerchantData*) >
   <!ATTLIST FindAcceptedPaymentBrand
     PayDirection  (Debit|Credit)  #REQUIRED
     CurrCodeType  NMTOKEN  'ISO4217-A'
     CurrCode  CDATA  #REQUIRED
     Amount  CDATA  #REQUIRED
     MerchantPayId  CDATA  #REQUIRED
     MerchantOrgId  CDATA  #IMPLIED
     WalletID  CDATA  #IMPLIED >
   Output Parameters
   o  Payment Brand Identifier - for insertion in the Brand List
      Component's Brand Element
   o  Payment Brand Name and language annotation - for insertion in
      the Brand List Component's Brand Element
   o  Payment Brand Logo Net Location - for insertion in the Brand
      List Component's Brand Element
   o  Payment Brand Narrative Description - for insertion in the
      Brand List Component's Brand Element
   o  (Brand) Packaged Content - further payment brand description
      for insertion in the Brand List Component's Brand Element

The Existing Payment Software returns an empty list of brand items, if it does not support any payment brand/payment protocol combination for the given payment parameters.

XML definition:

   <!ELEMENT FindAcceptedPaymentBrandResponse (BrandItem*) >
   <!ELEMENT BrandItem (BrandPackagedContent*) >
   <!ATTLIST BrandItem
     BrandId  CDATA  #REQUIRED
     xml:lang  NMTOKEN  #IMPLIED
     BrandName  CDATA  #REQUIRED
     BrandLogoNetLocn  CDATA  #REQUIRED
     BrandNarrative  CDATA  #IMPLIED >

Tables 4 and 5 explain the attributes and elements; Table 3 introduces the Error Codes.

4.1.2. Find Accepted Payment Protocol

This API function determines the instances of payment protocols (and optionally the payment brands) being accepted by the Payment Handler on behalf of the Merchant. The function might be called in two variants:
   o  With the Brand Identifier set on the input parameter list: The
      function responds with the payment protocols that fits to the
      submitted brand.
   o  Without any Brand Identifier - that allows the omission of the
      "Find Accepted Payment Brand" API call (cf. Section 4.1.1): This
      function responds with both the supported brand identifiers and
      the payment protocols being specified by the Brand Elements.
   Input Parameters
   o  Brand Identifier - returned by "Find Accepted Payment Brand"
   o  Payment Direction
   o  Currency Code and Currency
   o  Payment Amount
   o  Merchant Payment Identifier - Merchant's unique private
      reference to the payment transaction
   o  Merchant Organisation Identifier - used for distinction between
      multiple merchants that share the some IOTP merchant system
   o  Wallet Identifier - managed by the IOTP Application Core
   o  (Brand) Packaged Content - further payment brand description;
      returned by "Find Accepted Payment Brand"; this elements are
      only provided if the Brand Identifier is set
   o  Merchant Data - specific data used by the IOTP Payment Bridge
      which is managed in the IOTP Application Core.

XML definition:

   <!ELEMENT FindAcceptedPaymentProtocol (BrandPackagedContent*,
     MerchantData?) >
   <!ATTLIST FindAcceptedPaymentProtocol
     BrandId  CDATA  #IMPLIED
     PayDirection  (Debit|Credit)  #REQUIRED
     CurrCodeType  NMTOKEN  'ISO4217-A'
     CurrCode  CDATA  #REQUIRED
     Amount  CDATA  #REQUIRED
     MerchantPayId  CDATA  #REQUIRED
     MerchantOrgId  CDATA  #IMPLIED
     WalletID  CDATA  #IMPLIED >
   Output Parameters
   o  Payment Protocol Identifier - for insertion in the Brand List
      Component's Pay Protocol Element
   o  Protocol Brand Identifier - for insertion in the Protocol Brand
      Element of the Brand List Component's Brand Element
   o  Payment Protocol Name and language annotation- for insertion in
      the Brand List Component's Pay Protocol Element
   o  Payment Request Net Location - for insertion in the Brand List
      Component's Pay Protocol Element
   o  Secured Payment Request Net Location - for insertion in the
      Brand List Component's Pay Protocol Element
   o  Brand Item List (cf. Section 4.1.1) - there must be at least
      one element if no brand identifier has been provided on the
      input parameter list.
   o  (Protocol Amount) Packaged Content - for insertion in the Brand
      List Component's Protocol Amount Element
   o  (Pay Protocol) Packaged Content - for insertion in the Brand
      List Component's Pay Protocol Element
   o  Currency Amount element - quite similar to the definition in
      [IOTP], that contain
      - refined Currency Code and Currency - for insertion in the
        Brand List Component's Currency Amount Element
      - refined Payment Amount - for insertion in the Brand List
      Component's Currency Amount Element
   o  Brand - there must be at least one element in each Protocol
      Item if no brand identifier has been provided on the input
      parameter list.

XML definition:

   <!ELEMENT FindAcceptedPaymentProtocolResponse (ProtocolItem+,
     BrandItem*) >
   <!ELEMENT ProtocolItem (ProtocolAmountPackagedContent*,
     PayProtocolPackagedContent*
     CurrencyAmount+, Brand*,ProtocolBrand*)>
   <!ATTLIST ProtocolItem
     ProtocolId  CDATA  #REQUIRED
     ProtocolBrandId  CDATA  #IMPLIED
     xml:lang  NMTOKEN  #IMPLIED
     ProtocolName  CDATA  #REQUIRED
     PayReqNetLocn  CDATA  #IMPLIED
     SecPayReqNetLocn  CDATA  #IMPLIED >
   <!ELEMENT Brand EMPTY >
   <!ATTLIST Brand
     BrandId  CDATA  #REQUIRED >
   <!ELEMENT CurrencyAmount EMPTY >
   <!ATTLIST CurrencyAmount
     CurrCodeType  NMTOKEN  'ISO4217-A'
     CurrCode  CDATA  #IMPLIED
     Amount  CDATA  #IMPLIED >

Tables 4 and 5 explain the attributes and elements; Table 3 introduces the Error Codes.

4.1.3. Get Payment Initialization Data

This API function provides the remaining initialization data being required by the Consumer's or Payment Handler's Existing Payment Software. This function might be called both for "brand dependent" and "brand independent" transaction types. In either case, this function is called with one particular brand.
   Input Parameters
   o  Brand Identifier - returned by "Find Accepted Payment Brand"
   o  Merchant Payment Identifier - Merchant's unique private
      reference to the payment transaction
   o  Payment Direction
   o  Currency Code and Currency - from the Brand List Component's
      Currency Amount Element
   o  Payment Amount - from the Brand List Component's Currency
      Amount Element
   o  Payment Protocol Identifier - from the Brand List Component's
      Pay Protocol Element
   o  Protocol Brand Identifier - from the Protocol Brand Element
      which relates to the selected Brand Element, if any
   o  (TradingRoleData) Receiver Organization Identifier
   o  OkFrom, OkTo - identical to the entries of the Order Component
   Merchant Payment Identifier
   o  Merchant Organisation Identifier - used for distinction between
      multiple merchants that share the some IOTP merchant system
   o  Wallet Identifier and/or Pass Phrase
   Protocol Brand Element
   o  (Brand) Packaged Content - further payment brand description,
      from the Brand List Component's Brand Element
   o  (Protocol Amount) Packaged Content - further payment protocol
      description, from the Brand List Component's Protocol Amount
      Element
   o  (Pay Protocol) Packaged Content - further payment protocol
      description, from the Brand List Component's Pay Protocol
      Element
   o  (Protocol Brand) Packaged Content - further brand information,
      from the Protocol Brand Element of the Brand List Component
      which relates to the selected Brand Element, if any
   o  (Order) Packaged Content - further order description, from the
      Order Element
   o  three Brand Selection Info Packaged Content elements - copied
      from the Brand Selection Component on brand dependent purchases
   o  Brand - additional data about the payment brand
   o  Protocol Amount - additional data about the payment protocol
   o  Currency Amount - additional payment brand and currency
      specific data
   o  Merchant Data - specific data used by the IOTP Payment Bridge
      which is managed in the IOTP Application Core.

XML definition:

   <!ELEMENT GetPaymentInitializationData (ProtocolBrand?
     BrandPackagedContent*
     ProtocolAmountPackagedContent*,
     PayProtocolPackagedContent*,
     OrderPackagedContent*,
     BrandSelBrandInfoPackagedContent*,
     BrandSelProtocolAmountInfoPackagedContent*,
     BrandSelCurrencyAmountInfoPackagedContent*,
     MerchantData*) >
   <!ATTLIST GetPaymentInitializationData
     BrandId  CDATA  #REQUIRED
     MerchantPayId  CDATA  #REQUIRED
     PayDirection  (Debit|Credit)  #REQUIRED
     CurrCodeType  NMTOKEN  'ISO4217-A'
     CurrCode  CDATA  #REQUIRED
     Amount  CDATA  #REQUIRED
     ProtocolId  CDATA  #REQUIRED
     OkFrom  CDATA  #REQUIRED
     OkTo  CDATA  #REQUIRED
     ReceiverOrgId  CDATA  #IMPLIED
     MerchantOrgId  CDATA  #IMPLIED
     WalletID  CDATA  #IMPLIED
     Passphrase  CDATA  #IMPLIED >
   Output Parameters
   o  OkFrom, OkTo - for insertion in the Payment Component
   o  (TradingRoleData) Packaged Content - further payment protocol
      description; the Name Attribute of the packaged Content
      element must include "Payment:" as the prefix,
      for example "Payment:SET-OD".  For more information, see
      [SET/IOTP].
   o  (Order) Packaged Content - defaults to the supplied order
      packaged content if omitted.

XML definition:

   <!ELEMENT GetPaymentInitializationDataResponse
   (OrderPackagedContent*,
   TradingRoleDataPackagedContent*) >
   <!ATTLIST GetPaymentInitializationDataResponse
     OkFrom  CDATA  #IMPLIED
     OkTo  CDATA  #IMPLIED>

Tables 4 and 5 explain the attributes and elements; Table 3 introduces the Error Codes.

4.1.4. Inquire Authentication Challenge

This API function inquires any payment protocol specific authentication challenge value from the IOTP Payment Bridge. In Baseline IOTP this API function is called by the Merchant (or Financial Institution). The IOTP Application Core may propose a choice of algorithms to the IOTP Payment Bridge. However, the IOTP Payment Bridge may ignore the proposal and select some other algorithm.

The inquiry is assumed to be stateless. E.g., the IOTP Application Core may check the returned algorithm and stop transaction processing without notifying the IOTP Payment Bridge.

The IOTP Application Core may issue several API calls to the IOTP Payment Bridge to build up the IOTP Authentication Request Block. Any subsequently submitted choice of algorithms should be constrained by the accepted algorithms from earlier API responses.

The IOTP Payment Bridge responds with the Business Error Code if it does not provide any (more) authentication algorithms and challenges.

   Input Parameters
   o  Authentication Identifier - the authenticator may provide its
      payment identifier, i.e., Payment Handler or Merchant Payment
      Identifier.
   o  Wallet Identifier and/or Pass Phrase
   o  set of pre-selected algorithms for authentication

XML definition:

   <!ELEMENT InquireAuthChallenge (Algorithm*) >
   <!ATTLIST InquireAuthChallenge
     AuthenticationId  CDATA  #REQUIRED
     WalletID  CDATA  #IMPLIED
     Passphrase  CDATA  #IMPLIED >
   Output Parameters
   o  list of Authentication Challenge Packaged Contents - for
      insertion into the IOTP Authentication Request Component
   o  Algorithm Element - for insertion into the IOTP Authentication
      Request Component

XML definition:

   <!ELEMENT InquireAuthChallengeResponse (AuthReqPackagedContent*,
     Algorithm) >

4.1.5. Authenticate

The Consumer's IOTP Application Core defers payment protocol specific authentication processing and the current challenge value to the active IOTP Payment Bridge. Alternative authentication algorithms might be tried sequentially or offered to the user for selection.

Note that the IOTP Application Core has to consider both the current context and the algorithm in order to determine the responsible IOTP Payment Bridge.

Failed authentication is reported by the Business Error Code which might trigger the inquiry of the details ("Inquire Process State"). Final failures might be encoded by the process state "Failed".

   Input Parameters
   o  Authentication Identifier
   o  Wallet Identifier and/or Pass Phrase
   o  Authentication Challenge Packaged Content - copied from the
      IOTP Authentication Request Component
   o  Algorithm Element - copied from the IOTP Authentication Request
      Component

XML definition:

   <!ELEMENT Authenticate (Algorithm, AuthReqPackagedContent*) >
   <!ATTLIST Authenticate
     AuthenticationId  CDATA  #REQUIRED
     WalletID  CDATA  #IMPLIED
     Passphrase  CDATA  #IMPLIED >
   Output Parameters
   o  Authentication Response Packaged Content - for insertion into
      the IOTP Authentication Response Component

XML definition:

<!ELEMENT AuthenticateResponse (AuthResPackagedContent*) >

Tables 4 and 5 explain the attributes and elements; Table 3 introduces the Error Codes.

4.1.6. Check Authentication Response

This API function verifies the Consumer's payment protocol specific authentication response. In Baseline IOTP this API function is called by the Merchant (or the Financial Institution). It is called only if the counter party has responded with an IOTP Authentication Response Component within the Authentication Response Block. Of course, the IOTP Application Core traces the need of such an response.

Due to the authentication's statelessness, all parameters (algorithm, challenge and response) are submitted to the IOTP Payment Bridge. Authentication failure is reported by a Process State different from "CompletedOK".

   Input Parameters
   o  Authentication Identifier
   o  Wallet Identifier and/or Pass Phrase
   o  Authentication Challenge Packaged Content - generated by
      previous "Inquire Authentication Challenge" API call
   o  Algorithm Element
   o  Authentication Response Packaged Content - copied from the
      Authentication Response Component

XML definition:

   <!ELEMENT CheckAuthResponse (Algorithm, AuthReqPackagedContent*,
     AuthResPackagedContent*) >
   <!ATTLIST CheckAuthResponse
     AuthenticationId  CDATA  #REQUIRED
     WalletID  CDATA  #IMPLIED
     Passphrase  CDATA  #IMPLIED >
   Output Parameters

o Current Process (Authentication) State o Completion Code o Status Description and its language annotation

XML definition:

   <!ELEMENT CheckAuthResponseResponse EMPTY >
   <!ATTLIST CheckAuthResponseResponse
     ProcessState  (NotYetStarted |
      InProgress |
      Suspended |
      CompletedOk |
      Failed |
      ProcessError)#REQUIRED
     CompletionCode  NMTOKEN  #IMPLIED
      xml:lang  NMTOKEN  #IMPLIED
      StatusDesc  CDATA  #IMPLIED >

Tables 4 and 5 explain the attributes and elements; Table 3 introduces the Error Codes.

4.2. Brand Selection Related API Calls

4.2.1. Find Payment Instrument

This API function determines which instances of a Payment Brand, e.g., two Mondex cards, are present. The same physical card may even represent multiple payment instruments.

The IOTP Application Core supplies possible payment brand and payment protocol to the IOTP Payment Bridge that has to be considered when the IOTP Payment Bridge searches for appropriate payment instruments. This set represents the (sub)set of payment alternatives being supported by the Merchant. If the IOTP Application Cote has multiple possible payment brand/protocol, it can call this function in turn.

The Existing Payment Software responds with PayInstrument Elements with empty PayInstId attributes if it does not distinguish between different payment instruments for the particular payment alternatives.

Note that the Payment API assumes that the values of the attributes BrandId, ProtocolId, ProtocolBrandId and the currency amount suffice for the determination of the appropriate Packaged Content Element that will be transmitted to the Payment Handler later on.

   Input Parameters
   o  Brand Identifier - copied from the Brand List Component's Brand
      Element
   o  Payment Protocol Identifier and associated Protocol Brand
      Identifier
   o  Payment Direction - copied from the Brand List Component
   o  Currency Code and Currency - copied from the Currency Amount
      Element
   o  Payment Amount - copied from the Currency Amount Element
   o  Consumer Payment Identifier - Consumer's unique reference to
      the current payment transaction
   o  Wallet Identifier - managed by the IOTP Application Core
   o  (Brand) Packaged Content - further payment brand description;
      copied from the Brand List Component's Brand Element
   o  (Protocol Brand) Element - further information; copied from the
      Protocol Brand Element of the Brand List Component which
      relates to the Consumer selected Brand Element, if any.
   o  (Protocol Amount) Packaged Content - further payment protocol
      description, copied from the Brand List Component's Protocol
      Amount Element
   o  Element (Protocol) Packaged Content - further payment protocol
      description, copied from the Brand List Component's Pay
      Protocol Element

XML definition:

   <!ELEMENT FindPaymentInstrument (BrandPackagedContent*,
     ProtocolBrand?,
     PayProtocolPackagedContent*,
     ProtocolAmountPackagedContent*) >
   <!ATTLIST FindPaymentInstrument
     BrandId  CDATA  #REQUIRED
     ProtocolId  CDATA  #REQUIRED
     PayDirection  (Debit|Credit)  #REQUIRED
     CurrCodeType  NMTOKEN  'ISO4217-A'
     CurrCode  CDATA  #REQUIRED
     Amount  CDATA  #REQUIRED
     ConsumerPayId  CDATA  #REQUIRED
     WalletID  CDATA  #IMPLIED >
   Output Parameters
   o  The known Payment Instrument Identifiers, these are internal
      values
   o  The user-defined names of the payment instrument and their
      language encoding
      The Existing Payment Software responds with an empty list of
      identifiers, either if it does not distinguish between different
      payment instruments or if there are no registered payment
      instruments available despite brand support for at least one
      (unspecified) payment protocol.  In the latter case, the IOTP
      Payment Bridge has to request the registration of a suitable
      payment instrument at a subsequent step of the payment process.

XML definition:

   <!ELEMENT FindPaymentInstrumentResponse (PayInstrument*) >
   <!ELEMENT PayInstrument EMPTY >
   <!ATTLIST PayInstrument
     Id  CDATA  #REQUIRED
     xml:lang  NMTOKEN  #IMPLIED
     PayInstName  CDATA  #REQUIRED >

Tables 4 and 5 explain the attributes and elements; Table 3 introduces the Error Codes.

4.2.2. Check Payment Possibility

This API function checks whether a payment (both debit and credit) can go ahead. It can be used, for example, to check
   o  if there are sufficient funds available in a particular currency
      for an electronic cash payment brand,
   o  whether there is sufficient value space left on the payment
      instrument for payment refund,
   o  whether required system resources are available and properly
      configured, e.g., serial ports or baud rate,
   o  whether environment requirements are fulfilled, e.g., chip card
      reader presence or Internet connection.

If the payment method is based on external components, e.g., magnetic stripe or chip cards, and the check accesses the medium, the existing payment method should not mutually exclusive lock system resources, e.g., serial port or modem, that may also be required by other Existing Payment Software, e.g., multiple payment software components may share the same card reader. If this happens for API internal request processing, the function has to unlock these components prior to return. Otherwise, the payment may not proceed if the Consumer cancels immediately and decides to use another payment instrument. In this event the previous IOTP Payment Bridge is not notified about the change.

This function call happens immediately after the Consumer's payment instrument selection. For example, if the payment instrument is a chip card, that is not inserted in the chip card reader, the Consumer may be prompted for its insertion. However, the Consumer should be able to hit some 'skip' button, if the payment check is part of the actual payment protocol, too. Finally, the IOTP Payment Bridge may provide only a subset of these capabilities or may even directly generate a successful response without any checks.

   Input Parameters
   o  Brand Identifier - user selection
   o  Payment Instrument Identifier - user selection
   o  Currency Code and Currency Code Type - copied from the selected
      Currency Amount Element
   o  Payment Amount - copied from the selected Currency Amount Element
   o  Payment Direction - copied from the selected Trading Protocol
      Option Block
   o  Protocol Identifier - copied from the selected Pay Protocol
      Element
   o  Protocol Brand Identifier - copied from the selected Protocol
      Brand Element of the Brand List Component which relates to the
      selected Brand Element, if any
   o  Consumer Payment Identifier - Consumer's unique reference to the
      current payment transaction
   o  Wallet Identifier and/or Pass Phrase
   o  (Brand) Packaged Content - copied from the selected Brand Element
   o  (Protocol Amount) Packaged Content - copied from the selected
      Protocol Amount Element
   o  (Protocol) Packaged Content - copied from the selected Pay
      Protocol Element
   o  (Protocol Brand) Packaged Content - copied from the selected
      Protocol Brand Element of the Brand List Component which relates
      to the selected Brand Element, if any

XML definition:

   <!ELEMENT CheckPaymentPossibility (BrandPackagedContent*,
     ProtocolBrand?
     ProtocolAmountPackagedContent*,
     PayProtocolPackagedContent*>
   <!ATTLIST CheckPaymentPossibility
     BrandId  CDATA  #REQUIRED
     PaymentInstrumentId  CDATA  #IMPLIED
     PayDirection  (Debit|Credit)  #REQUIRED
     CurrCodeType  NMTOKEN  'ISO4217-A'
     CurrCode  CDATA  #REQUIRED
     Amount  CDATA  #REQUIRED
     ProtocolId  CDATA  #REQUIRED
     ConsumerPayId  CDATA  #REQUIRED
     WalletID  CDATA  #IMPLIED
     Passphrase  CDATA  #IMPLIED >
   Output Parameters
   o  three Brand Selection Info Packaged Content elements - for
      insertion into the Brand Selection component
   o  Brand - additional data about the payment brand
   o  Protocol Amount - additional data about the payment protocol
   o  Currency Amount - additional payment brand and currency specific
      data
XML definition:
   <!ELEMENT CheckPaymentPossibilityResponse
     (BrandSelBrandInfoPackagedContent*,
     BrandSelProtocolAmountInfoPackagedContent*,
     BrandSelCurrencyAmountInfoPackagedContent*) >
   <!ATTLIST CheckPaymentPossibilityResponse >

Tables 4 and 5 explain the attributes and elements; Table 3 introduces the Error Codes.

4.3. Payment Transaction Related API calls

These Payment API calls may be made either by the Consumer's or Payment Handler's IOTP Application Core.

4.3.1. Start Payment Consumer

This API function initiates the actual payment transaction at the Consumer side. The IOTP Payment Bridge and the Existing Payment Software perform all necessary initialization and preparation for payment transaction processing. This includes the reservation of external periphery. E.g., 1) the Consumer's chip card reader needs to be protected against access from other software components, 2) the insertion of the chip card may be requested, 3) the Internet connection may be re-established, or 4) the Payment Handler may open a mutual exclusive session to the security hardware.

The IOTP Payment Bridge monitors the payment progress and stores the current payment states such that resumption - even after power failures - remains possible. Note that the IOTP Application Core supplies only a subset of the following input parameter to the associated resumption API function and refers to the payment transaction through the party's payment identifier.

   Input Parameters
   o  Brand Identifier - copied from the selected Brand Element
   o  Payment Instrument Identifier - the user selection
   o  Currency Code and Currency - copied from the selected Currency
      Amount Element
   o  Payment Amount - copied from the selected Currency Amount
      Element
   o  Payment Direction - copied from the Brand List Component
   o  Protocol Identifier - copied from the selected Payment Protocol
      Element
   o  Protocol Brand Element - further information; copied from the
      Protocol Brand Element of the Brand List Component which
      relates to the selected Brand Element, if any
   o  OkFrom, OkTo - copied from the Payment Component
   o  Consumer Payment Identifier - Consumer's unique reference to
      the current payment transaction
   o  Wallet Identifier and/or Pass Phrase
   o  Call Back Function - used for end user notification/logging
      purposes
   o  Call Back Language List.  This list is required if the Call Back
      Function is set
   o  (Brand) Packaged Content - further payment brand description;
      copied from the selected Brand Element's content
   o  (Protocol Amount) Packaged Content - further payment protocol
      description; copied from the selected Protocol Amount Element's
      content
   o  (Payment Protocol) Packaged Content - further payment protocol
      description; copied from the selected Pay Protocol Element's
      content
   o  (Order) Packaged Content - further order description, copied
      from the Order Component

XML definition:

   <!ELEMENT StartPaymentConsumer (BrandPackagedContent*,
     ProtocolBrand?
     ProtocolAmountPackagedContent*,
     PayProtocolPackagedContent*,
     OrderPackagedContent*) >
   <!ATTLIST StartPaymentConsumer
     BrandId  CDATA  #REQUIRED
     PaymentInstrumentId  CDATA  #IMPLIED
     CurrCodeType  NMTOKEN  'ISO4217-A'
     CurrCode  CDATA  #REQUIRED
     Amount  CDATA  #REQUIRED
     PayDirection  (Debit|Credit)  #REQUIRED
     ProtocolId  CDATA  #REQUIRED
     ProtocolBrandId  CDATA  #IMPLIED
     OkFrom  CDATA  #REQUIRED
     OkTo  CDATA  #REQUIRED
     ConsumerPayId  CDATA  #REQUIRED
     WalletID  CDATA  #IMPLIED
     Passphrase  CDATA  #IMPLIED
     CallBackFunction  CDATA  #IMPLIED
     CallBackLanguageList  NMTOKENS  #IMPLIED >
   Output Parameters
   o  Continuation Status
   o  (Payment Scheme) Packaged Content - for insertion into the
      Payment Scheme Component of the IOTP Payment Request Block

The IOTP Application Core is allowed to reissue this request several times on failed analyses of the response.

XML definition:

   <!ELEMENT StartPaymentConsumerResponse
     (PaySchemePackagedContent*) >
   <!ATTLIST StartPaymentConsumerResponse
     ContStatus  (End|Continue)  #REQUIRED >

Tables 4 and 5 explain the attributes and elements; Table 3 introduces the Error Codes.

4.3.2. Start Payment Payment Handler

This API function initializes the Consumer initiated payment transaction at the Payment Handler's side. Similar to the Consumer's system, the IOTP Payment Bridge and the Existing Payment Software perform all necessary initialization and preparation for payment transaction processing.
   Input Parameters
   o  Brand Identifier  - copied from the Consumer selected Brand
      Element
   o  Consumer Payment Identifier - copied from the Payment Scheme
      Component
   o  Currency Code and Currency - copied from the Consumer selected
      Currency Amount Element
   o  Payment Amount - copied from the Consumer selected Currency
      Amount Element
   o  Payment Direction - copied from the Brand List Component
   o  Protocol Identifier  - copied from the Consumer selected
      Payment Protocol Element
   o  Protocol Brand Identifier - copied from the Brand Protocol
      Element of the Brand List Component which relates to the
      Consumer selected Brand Element, if any
   o  OkFrom, OkTo - copied from the Payment Component
   o  Payment Handler Payment Identifier - Payment Handler's unique
      reference to the current payment transaction
   o  Merchant Organisation Identifier -  copied from the Merchant's
      Organisation Element
   o  Wallet Identifier - renaming to till identifier neglected -
      and/or Pass Phrase
   o  Call Back Function - used for end user notification/logging
      purposes
   o  Call Back Language List.  This list is required if the call
      back function is set
   o  (Brand) Packaged Content - further payment brand description;
      copied from the Consumer selected Brand Element's content
   o  (Protocol Brand) Packaged Content - further information; copied
      from the Protocol Brand Element of the Brand List Component
      which relates to the Consumer selected Brand Element, if any.
   o  (Protocol Amount) Packaged Content - further payment protocol
      description; copied from the Consumer selected Protocol Amount
      Element's content
   o  (Protocol) Packaged Content - further payment protocol
      description; copied from the Consumer selected Pay Protocol
      Element's content
   o  (TradingRoleData) Packaged Content - further payment protocol
      description; the Name Attribute of the packaged contents must
      include "Payment:" as the prefix, for example "Payment:SET-OD".
      For more information, see [SET/IOTP].
   o  Three Brand Selection Info Packaged Content Elements - copied
      from the Brand Selection Component
   o  Brand - additional data about the payment brand
   o  Protocol Amount - additional data about the payment protocol
   o  Currency Amount - additional payment brand and currency
      specific data
   o  (Payment Scheme) Packaged Content.

XML definition:

   <!ELEMENT StartPaymentPaymentHandler (BrandPackagedContent*,
     ProtocolBrand?,
     ProtocolAmountPackagedContent*,
     PayProtocolPackagedContent*,
     BrandSelBrandInfoPackagedContent*,
     BrandSelProtocolAmountInfoPackagedContent*,
     BrandSelCurrencyAmountInfoPackagedContent*,
     TradingRoleDataPackagedContent*,
     PaySchemePackagedContent*) >
   <!ATTLIST StartPaymentPaymentHandler
     BrandId  CDATA  #REQUIRED
     ConsumerPayId  CDATA  #IMPLIED
     CurrCodeType  NMTOKEN  'ISO4217-A'
     CurrCode  CDATA  #REQUIRED
     Amount  CDATA  #REQUIRED
     PayDirection  (Debit|Credit)  #REQUIRED
     ProtocolId  CDATA  #REQUIRED
     OkFrom  CDATA  #REQUIRED
     OkTo  CDATA  #REQUIRED
     PaymentHandlerPayId  CDATA  #REQUIRED
     MerchantOrgId  CDATA  #REQUIRED
     WalletID  CDATA  #IMPLIED
     Passphrase  CDATA  #IMPLIED
     CallBackFunction  CDATA  #IMPLIED
     CallBackLanguageList  NMTOKENS  #IMPLIED >
   Output Parameters
   o  Continuation Status
   o  (Payment Scheme) Packaged Content - for insertion into the
      Payment Scheme Component of the IOTP Payment Exchange Block

The response message must contain payment schema data if the continuation status signals "Continue". The IOTP Application Core is allowed to reissue this request several times on failed analyses of the response.

XML definition:

   <!ELEMENT StartPaymentPaymentHandlerResponse
     (PaySchemePackagedContent*) >
   <!ATTLIST StartPaymentPaymentHandlerResponse
     ContStatus  (End|Continue)  #REQUIRED >

Tables 4 and 5 explain the attributes and elements; Table 3 introduces the Error Codes.

4.3.3. Resume Payment Consumer

This API function resumes a previously suspended payment at the Consumer side. Resumption includes the internal inquiry of the payment transaction data, e.g., payment amount, protocol identifier, and the whole initialization as it has been applied on the "Start Payment Consumer" API request.

It is up to the IOTP Application Core to decide whether an IOTP Payment Request Block or a IOTP Payment Exchange Block needs to be generated. One indicator might be the receipt of a previous IOTP Payment Exchange Block from the Payment Handler, e.g., the knowledge of the Payment Handler Payment Identifier.

   Input Parameters

o Consumer Payment Identifier o Wallet Identifier and/or Pass Phrase

   o  Call Back Function - used for end user notification/logging
      purposes

XML definition:

   <!ELEMENT ResumePaymentConsumer EMPTY >
   <!ATTLIST ResumePaymentConsumer
     ConsumerPayId  CDATA  #REQUIRED
     WalletID  CDATA  #IMPLIED
     Passphrase  CDATA  #IMPLIED
     CallBackFunction  CDATA  #IMPLIED
     CallBackLanguageList  NMTOKENS  #IMPLIED >
   Output Parameters
   o  Continuation Status
   o  (Payment Scheme) Packaged Content - for insertion in the
      Payment Scheme Component of the next IOTP message (Payment
      Exchange or Request Block).

The IOTP Application Core is allowed to reissue this request several times on failed analyses of the response. However, the IOTP Payment Bridge might reject the resumption request by using the "AttNotSupp" Error Code "naming" the Consumer Payment Identifier attribute. Then the Consumer has to apply normal error processing to the current (sub-)transaction and to issue a new Payment Request Block to the Payment Handler.

XML definition:

   <!ELEMENT ResumePaymentConsumerResponse
     (PaySchemePackagedContent*) >
   <!ATTLIST ResumePaymentConsumerResponse
     ContStatus  (End|Continue)  #REQUIRED >

Tables 4 and 5 explain the attributes and elements; Table 3 introduces the Error Codes.

4.3.4. Resume Payment Payment Handler

This API function resumes a payment at the Payment Handler side.
   Input Parameters
   o  Payment Handler Payment Identifier
   o  Wallet Identifier - renaming to till identifier neglected - and
      Pass Phrase
   o  Call Back Function - used for end user notification/logging
      purposes
   o  Call Back Language List.  This list is required if the Call Back
      Function is set
   o  (Payment Scheme) Packaged Content - copied from the Payment
      Scheme Component of the received IOTP message (Payment Exchange
      or Request Block).

XML definition:

   <!ELEMENT ResumePaymentPaymentHandler
     (PaySchemePackagedContent*) >
   <!ATTLIST ResumePaymentPaymentHandler
     PaymentHandlerPayId  CDATA  #REQUIRED
     WalletID  CDATA  #IMPLIED
     Passphrase  CDATA  #IMPLIED
     CallBackFunction  CDATA  #IMPLIED
     CallBackLanguageList  NMTOKENS  #IMPLIED >
   Output Parameters
   o  Continuation Status
   o  (Payment Scheme) Packaged Content - for insertion in the
      Payment Scheme Component of the next Payment Exchange Block.

The response message contains payment schema specific data if the continuation status signals "Continue". The IOTP Application Core is allowed to reissue this request several times on failed analyses of the response.

XML definition:

   <!ELEMENT ResumePaymentPaymentHandlerResponse
   (PaySchemePackagedContent*) >
   <!ATTLIST ResumePaymentPaymentHandlerResponse
     ContStatus  (End|Continue)  #REQUIRED >

Tables 4 and 5 explain the attributes and elements; Table 3 introduces the Error Codes.

4.3.5. Continue Process

This API function passes one specific IOTP Payment Scheme Component, i.e., the encapsulated Packaged Content elements, received from the counter party (e.g., Consumer) to the IOTP Payment Bridge and responds with the next IOTP Payment Scheme Component for submission to the counter party.
   Input Parameters
   o  Payty's Payment Identifier
   o  Process (Transaction) Type which distinguishes between Payments
      and Inquiries.
   o  Wallet Identifier and/or Pass Phrase
   o  (Payment Scheme) Packaged Content - copied from the Payment
      Scheme Component of the received Payment Exchange Block or from
      the Error Block.

Each party should set the payment identifier with the local identifier (Consumer: ConsumerPayId; Merchant: MerchantPayId; Payment Handler: PaymentHandlerPayId).

XML definition:

   <!ELEMENT ContinueProcess (PaySchemePackagedContent+) >
   <!ATTLIST ContinueProcess
     PayId  CDATA  #REQUIRED
     ProcessType  (Payment | Inquiry) 'Payment'
     WalletID  CDATA  #IMPLIED
     Passphrase  CDATA  #IMPLIED >
   Output Parameters
   o  Continuation Status
   o  (Payment Scheme) Packaged Content - for insertion in the
      Payment Scheme Component of the next Payment Exchange Block or
      final Payment Response Block

The response message contains payment schema data if the continuation status signals "Continue". The IOTP Payment Bridge must signal "End", if the payment scheme data was received within an IOTP Error Block containing an Error Component with severity HardError.

XML definition:

   <!ELEMENT ContinueProcessResponse (PaySchemePackagedContent*) >
   <!ATTLIST ContinueProcessResponse
     ContStatus  (End|Continue)  #REQUIRED >

Tables 4 and 5 explain the attributes and elements; Table 3 introduces the Error Codes.

4.3.6. Change Process State

The IOTP Application Core changes the current payment status by this request. The IOTP Payment Bridge may be notified about business level normal termination, cancellation, suspension, and processing errors. Notification happens by requesting the intended process state.

The IOTP Payment Bridge processes the status change and reports the result.

The IOTP Application Core has to analyze any returned process status in order to check whether the IOTP Payment Bridge has agreed to or declined the status switch. E.g., the submitted Process State "CompleteOk" may lead to the Payment Status "Failed" if the payment transaction has already failed.

Transaction Suspension is notified by the newly introduced Process State "Suspended". The other attribute values have been taken from the IOTP specification.

This API function might be called by the Consumer, Merchant, or Payment Handler for each payment transaction anytime after the issuance of "FindPaymentInstrument" to the IOTP Payment Bridge by the Consumer, the issuance of "FindAcceptedPaymentBrand" by the Merchant, or the issuance of "StartPaymentPaymentHandler" by the Payment Handler.

The Process States "CompletedOk", "Failed", and "ProcessError" are final in the sense that they can not be changed on subsequent calls. However, the API function should not return with an error code if such an incompatible call has been issued. Instead it should report the old unchanged Process State.

Unknown payment transactions are reported by the Error Code "AttValInvalid" pointing to the PayId attribute.

   Input Parameters
   o  Party's Payment Identifier
   o  intended Payment Status
   o  intended Completion Code
   o  Process (Transaction) Type which distinguishes between Payments
      and Inquiries.
   o  Wallet Identifier and/or Pass Phrase
XML definition:
   <!ELEMENT ChangeProcessState EMPTY >
   <!ATTLIST ChangeProcessState
     PayId  CDATA  #REQUIRED
     ProcessState  (NotYetStarted |
      InProgress |
      Suspended |
      CompletedOk |
      Failed |
      ProcessError)  #REQUIRED
     CompletionCode  NMTOKEN  #IMPLIED
     ProcessType  (Payment | Inquiry) 'Payment'
     WalletID  CDATA  #IMPLIED
     Passphrase  CDATA  #IMPLIED >
   Output Parameters

o Process State and Percent Complete o Completion Code o Status Description and its language annotation

XML definition:

   <!ELEMENT ChangeProcessStateResponse EMPTY >
   <!ATTLIST ChangeProcessStateResponse
     ProcessState  (NotYetStarted |
      InProgress |
      Suspended |
      CompletedOk |
      Failed |
      ProcessError)  #REQUIRED
     PercentComplete  CDATA  #IMPLIED
     CompletionCode  NMTOKEN  #IMPLIED
     xml:lang  NMTOKEN  #IMPLIED
     StatusDesc  CDATA  #IMPLIED >

Tables 4 and 5 explain the attributes and elements; Table 3 introduces the Error Codes.

4.4. General Inquiry API Calls

The following calls are not necessarily assigned to a payment transaction and may be issued at any time. There are no dependencies on any other calls.

4.4.1. Remove Payment Log

The IOTP Application Core notifies the IOTP Payment Bridge and/or the corresponding Existing Payment Software via IOTP Payment Bridge that any record in the Payment Log file, that deals with the listed payment transaction, might be removed.
   Input Parameters

o Party's Payment Identifier o Wallet Identifier and/or Pass Phrase

XML definition:

   <!ELEMENT RemovePaymentLog EMPTY >
   <!ATTLIST RemovePaymentLog
     PayId  CDATA  #REQUIRED
     WalletID  CDATA  #IMPLIED
     Passphrase  CDATA  #IMPLIED >
   Output Parameters

XML definition:

<!ELEMENT RemovePaymentLogResponse EMPTY > <!ATTLIST RemovePaymentLogResponse >

Tables 4 and 5 explain the attributes and elements; Table 3 introduces the Error Codes.

4.4.2. Payment Instrument Inquiry

This API function retrieves the properties of the Payment Instrument. The Payment Instrument Identifier could be omitted if this identifier is derived by other means, e.g., by analysis of the currently inserted chip card. If the Payment instrument could not uniquely determined, the IOTP Payment Bridge may provide suitable dialogs for user input.

E.g., this API function might be used during problem resolution with the Customer Care Provider of the issuer of the payment instrument, in order to inquire payment instrument specific values.

   Input parameters

o Brand Identifier o Payment Instrument Identifier o Protocol Identifier

   o  Wallet Identifier and/or Pass Phrase
   o  Property Type List - sequence of values whose language is
      identified by xml:lang
   o  (Brand) PackagedContent Content - further payment brand
      description
   o  Protocol Brand Content - further payment brand information
   o  (Protocol Amount) PackagedContent Content - further payment
      protocol description
   o  (Pay Protocol) PackagedContent Content - further payment
      protocol description

The codes in the property type list are of two types:

   o  generic codes which apply to all payment methods but might be
      unavailable
   o  Payment Brand specific codes.

Generic codes for the Property Type List are:

   Property Type         Meaning
   Balance               Current balance
   Limit                 Maximum balance
   PaymentLimit          Maximum payment transaction limit
   Expiration            Expiration date
   Identifier            Issuer assigned identifier of the payment
                         instrument.  Usually, it does not match with
                         the API's payment instrument identifier.
   LogEntries            Number of stored payment transaction
                         entries.  The entries are numbered from 0
                         (the most recent) to some non-negative
                         value for the oldest entry.
   PayAmountn            Payment Amount of the n-th recorded payment
                         transaction, n may negative
   PayPartyn             Remote party of the n-th payment recorded
                         transaction, n may negative
   PayTimen              Time of the n-th payment recorded
                         transaction, n may negative

XML definition:

   <!ELEMENT PaymentInstrumentInquiry (BrandPackagedContent*,
     ProtocolBrand?,
     ProtocolAmountPackagedContent*,
     PayProtocolPackagedContent*) >
   <!ATTLIST PaymentInstrumentInquiry
     BrandId  CDATA  #REQUIRED
     PaymentInstrumentId  CDATA  #IMPLIED
     ProtocolId  CDATA  #REQUIRED
     PropertyTypeList  NMTOKENS  #REQUIRED
     xml:lang  NMTOKEN  #IMPLIED
     WalletID  CDATA  #IMPLIED
     Passphrase  CDATA  #IMPLIED >
   Output parameters
   o  a list of zero or more unavailable property values whose
      language are identified by xml:lang.
   o  a list of zero or more sets of "Properties Types", "Property
      Values" and "Property Descriptions"

XML definition:

   <!ELEMENT PaymentInstrumentInquiryResponse
     (PaymentInstrumentProperty*) >
   <!ATTLIST PaymentInstrumentInquiryResponse
     xml:lang  NMTOKEN  #REQUIRED
     UnavailablePropertyList NMTOKENS  #IMPLIED >
   <!ELEMENT PaymentInstrumentProperty EMPTY >
   <!ATTLIST PaymentInstrumentProperty
     PropertyType  NMTOKEN  #REQUIRED
     PropertyValue  CDATA  #REQUIRED
     PropertyDesc  CDATA  #REQUIRED >

Tables 4 and 5 explain the attributes and elements; Table 3 introduces the Error Codes.

4.4.3. Inquire Pending Payment

This API function reports the party's payment identifiers of any pending payment transactions that the IOTP Payment Bridge/Existing Payment Software recommends be completed or suspended prior to the processing of new payment transactions. It does not respond with further transaction details. These have to be requested with "Inquire Process State".

Note that the IOTP Payment Bridge has to respond without the benefit of any pass phrase if there exist no pending payment transaction. But if there are some pending payment transactions, the IOTP Payment Bridge may refuse the immediate response and may instead request the appropriate pass phase from the IOTP Application Core.

   Input Parameters
   o  Wallet Identifier and/or Passphrase
XML definition:
   <!ELEMENT InquirePendingPayment EMPTY >
   <!ATTLIST InquirePendingPayment
     WalletId  CDATA  #IMPLIED
     Passphrase  CDATA  #IMPLIED >
   Output Parameters
   o  Party's Payment Identifier

XML definition:

<!ELEMENT InquirePendingPaymentResponse (PaymentId*) >

   <!ELEMENT PaymentId EMPTY >
   <!ATTLIST PaymentId
     PayId  CDATA  #REQUIRED >

Tables 4 and 5 explain the attributes and elements; Table 3 introduces the Error Codes.

4.5. Payment Related Inquiry API Calls

4.5.1. Check Payment Receipt

This function is used by the Consumer and might be used by the Payment Handler to check the consistency, validity, and integrity of IOTP payment receipts which might consist of Packaged Content Elements
   o  from the IOTP Payment Receipt Component - provided by the Payment
      Handler's "Inquire Process State" API call shortly before payment
      completion,
   o  from Payment Scheme Components being exchanged during the actual
      payment, or
   o  being returned by the Consumer's "Inquire Process State" API call
      shortly before payment completion

The IOTP Application Core has to check the PayReceiptNameRefs attribute of the IOTP Payment Receipt Component and to supply exactly the Packaged Content Elements being referred to.

Failed verification is returns a business error. Note that this Payment API assumes that any payment receipt builds upon a subset of elements with reference to [IOTP]. Furthermore, the Packaged Content Element have to be distinguishable by their Name attribute.

   Input Parameters

o Party's Payment Identifier o Wallet Identifier and/or Pass Phrase o All Packaged Content Elements in the payment receipt

XML definition:

   <!ELEMENT CheckPaymentReceipt (PackagedContent*) >
   <!ATTLIST CheckPaymentReceipt
     PayId  CDATA  #REQUIRED
     WalletID  CDATA  #IMPLIED
     Passphrase  CDATA  #IMPLIED >
   Output Parameters

XML definition:

<!ELEMENT CheckPaymentReceiptResponse EMPTY > <!ATTLIST CheckPaymentReceiptResponse >

Tables 4 and 5 explain the attributes and elements; Table 3 introduces the Error Codes.

4.5.2. Expand Payment Receipt

This API function expands any IOTP payment receipt into a form which may be used for display or printing purposes. "Check Payment Receipt" should be used first if there is any question of the payment receipt containing errors.

The same conventions apply to the input parameter as for "Check Payment Receipt" (cf. Section 4.5.1).

   Input Parameters

o Party's Payment Identifier o Wallet Identifier and/or Pass Phrase o All Packaged Content Elements that build the payment receipt XML definition:

   <!ELEMENT ExpandPaymentReceipt (PackagedContent*) >
   <!ATTLIST ExpandPaymentReceipt
     PayId  CDATA  #REQUIRED
     WalletID  CDATA  #IMPLIED
     Passphrase  CDATA  #IMPLIED >
   Output Parameters
   o  Brand Identifier
   o  Protocol specific Brand Identifier
   o  Payment Instrument Identifier
   o  Currency Code and Currency Code Type
   o  Payment Amount
   o  Payment Direction
   o  Time Stamp - issuance of the receipt
   o  Protocol Identifier
   o  Protocol specific Transaction Identifier - this is an internal
      reference number which identifies the payment
   o  Consumer Description, Payment Handler Description, and a
      language annotation
   o  Style Sheet Net Location
   o  Payment Property List.  A list of type/value/description triples
      which contains additional information about the payment which
      is not covered by any of the other output parameters; property
      descriptions have to consider the language annotation.

The Style Sheet Net Location refers to a Style Sheet (e.g., [XSLT]) that contains presentation information about the reported XML encoded data.

XML definition:

   <!ELEMENT ExpandPaymentReceiptResponse (PaymentProperty*) >
   <!ATTLIST ExpandPaymentReceiptResponse
     BrandId  CDATA  #IMPLIED
     PaymentInstrumentId  CDATA  #IMPLIED
     Amount  CDATA  #IMPLIED
     CurrCodeType  NMTOKEN  #IMPLIED
     CurrCode  CDATA  #IMPLIED
     PayDirection  (Debit|Credit)  #IMPLIED
     TimeStamp  CDATA  #IMPLIED
     ProtocolId  CDATA  #IMPLIED
     ProtocolBrandId  CDATA  #IMPLIED
     ProtocolTransId  CDATA  #IMPLIED
     xml:lang  NMTOKEN  #IMPLIED
     ConsumerDesc  CDATA  #IMPLIED
     PaymentHandlerDesc  CDATA  #IMPLIED
     StyleSheetNetLocn  CDATA  #IMPLIED>
   <!ELEMENT PaymentProperty EMPTY >
   <!ATTLIST PaymentProperty
     PropertyType  NMTOKEN  #REQUIRED
     PropertyValue  CDATA  #REQUIRED
     PropertyDesc  CDATA  #REQUIRED >

The Existing Payment Software should return as many attributes as possible from the supplied IOTP Payment Receipt. The payment supplement defines the attribute values for the payment properties.

Tables 4 and 5 explain the attributes and elements; Table 3 introduces the Error Codes.

4.5.3. Inquire Process State

This API function returns the current payment state and optionally further Packaged Content Elements that form the payment receipt. Called by the Payment Handler, the IOTP Payment Bridge might respond with data intended for inclusion in the IOTP Payment Receipt Component's Packaged Content. When the Consumer calls this function shortly before payment completion, it may respond with further items of the payment receipt. Such items might be created by a chip card.
   Input Parameters

o Party's Payment Identifier o Wallet Identifier and/or Pass Phrase

XML definition:

   <!ELEMENT InquireProcessState EMPTY >
   <!ATTLIST InquireProcessState
     PayId  CDATA  #REQUIRED
     WalletID  CDATA  #IMPLIED
     Passphrase  CDATA  #IMPLIED >
   Output Parameters
   o  Current Process State and Percent Complete
   o  Completion Code
   o  Status Description and its language annotation
   o  Payment Receipt Name References to all Packaged Content
      Elements that build the payment receipt (cf. Section 4.5.1),
      even if they have not been created so far (Consumer's share)
   o  Any Packaged Content Element being available that form the
      payment receipt

The IOTP provides a linking capability to the payment receipt delivery. Instead of encapsulating the whole payment specific data into the packaged content of the payment receipt, other Payment Scheme Components' Packaged Content might be referred to.

XML definition:

   <!ELEMENT InquireProcessStateResponse
   (PackagedContent*) >
   <!ATTLIST InquireProcessStateResponse
     ProcessState  (NotYetStarted |
      InProgress |
      Suspended |
      CompletedOk |
      Failed |
      ProcessError)  #REQUIRED
     PercentComplete  CDATA  #IMPLIED
     CompletionCode  NMTOKEN  #IMPLIED
     xml:lang  NMTOKEN  #IMPLIED
     StatusDesc  CDATA  #IMPLIED
     PayReceiptNameRefs  NMTOKENS  #IMPLIED >

Tables 4 and 5 explain the attributes and elements; Table 3 introduces the Error Codes.

4.5.4. Start Payment Inquiry

This API function responds with any additional payment scheme specific data that is needed by the Payment Handler for Consumer initiated payment transaction inquiry processing. Probably, the IOTP Payment Bridge (or the corresponding Existing Payment Software) has to determine the payment related items that were provided with the "Start Payment Consumer" API function call.
   Input Parameters

o Consumer Payment Identifier o Wallet Identifier and/or Pass Phrase XML definition:

   <!ELEMENT StartPaymentInquiry EMPTY >
   <!ATTLIST StartPaymentInquiry
     ConsumerPayId  CDATA  #REQUIRED
     WalletID  CDATA  #IMPLIED
     Passphrase  CDATA  #IMPLIED >
   Output Parameters
   o  (Payment Scheme) Packaged Content - intended for insertion in
      the Payment Scheme Component of  the Inquiry Request Block

XML definition:

   <!ELEMENT StartPaymentInquiryResponse
     (PaySchemePackagedContent*) >

Tables 4 and 5 explain the attributes and elements; Table 3 introduces the Error Codes.

4.5.5. Inquire Payment Status

The Payment Handler calls this API function for Consumer initiated inquiry processing. It differs from the previous "Inquire Process State" API function by the optional inclusion of payment scheme specific data. The response may encapsulate further details about the payment transaction.
   Input Parameters
   o  Payment Handler Payment Identifier
   o  Wallet Identifier and/or Pass Phrase
   o  (Payment Scheme) Packaged Content - copied from the Inquiry
      Request Block's Payment Scheme Component

XML definition:

   <!ELEMENT InquirePaymentStatus (PaySchemePackagedContent*) >
   <!ATTLIST InquirePaymentStatus
     PaymentHandlerPayId  CDATA  #REQUIRED
     WalletID  CDATA  #IMPLIED
     Passphrase  CDATA  #IMPLIED >
   Output Parameters

o Current Process State o Completion Code

   o  Status Description and its language annotation
   o  (Payment Scheme) Packaged Content - intended for insertion in
      the Payment Scheme Component of the Inquiry Response Block

XML definition:

   <!ELEMENT InquirePaymentStatusResponse
   (PaySchemePackagedContent*) >
   <!ATTLIST InquirePaymentStatusResponse
     PaymentHandlerPayId  CDATA  #REQUIRED
     ProcessState  (NotYetStarted |
      InProgress |
      Suspended |
      CompletedOk |
      Failed |
      ProcessError)  #REQUIRED
     CompletionCode  NMTOKEN  #IMPLIED
     xml:lang  NMTOKEN  #IMPLIED
     StatusDesc  CDATA  #IMPLIED >

Tables 4 and 5 explain the attributes and elements; Table 3 introduces the Error Codes.

4.6. Other API Calls

4.6.1. Manage Payment Software

The following API function notifies the IOTP Payment Bridge about the intended registration, modification, or deletion of a payment instrument. The actual processing is up to the IOTP Payment Bridge.

This API request may also be used to activate the IOTP Payment Bridge (and the corresponding Existing Payment Software) for general administration purposes.

   Input Parameters
   o  Brand Identifier
   o  Protocol Identifier
   o  Any action code:
   o  New - add new payment method / instrument
   o  Update - change the payment method's / instrument's data
   o  Delete - delete a payment method / instrument
   o  Wallet Identifier and/or Pass Phrase
   o  (Brand) Packaged Content - further payment brand description
   o  (Pay Protocol) Packaged Content - further payment protocol
      description
   o  (Protocol Amount) Packaged Content - further payment protocol
      description

If the Action attribute is set, the Brand and Protocol Identifier have to also be set. The IOTP Payment Bridge has to provide the required user dialogs and selection mechanisms. E.g., updates and deletions may require the selection of the payment instrument. A new wallet might be silently generated on the supplement of a new Wallet Identifier or after an additional end user acknowledge. The IOTP Application Core should not provide any pass phrases for new wallets. Instead, the IOTP Payment Bridge has to request and verify them, which may return their value to the IOTP Application Core in plain text. In addition, the IOTP Payment Bridge returns the supported authentication algorithms when a new brand and protocol pair has been registered.

If the "Action" attribute is omitted, the IOTP Payment Bridge which is responsible for the Existing Payment Software pops up in a general interactive mode.

XML definition:

   <!ELEMENT ManagePaymentSoftware (BrandPackagedContent*,
     ProtocolAmountPackagedContent*,
     PayProtocolPackagedContent*) >
   <!ATTLIST ManagePaymentSoftware
     BrandId  CDATA  #IMPLIED
     ProtocolId  CDATA  #IMPLIED
     Action  (New |
      Update |
      Delete)  #IMPLIED
     WalletID  CDATA  #IMPLIED
     Passphrase  CDATA  #IMPLIED >
   Output Parameters

o An action code: o New - added new wallet o Update - changed wallet's configuration o Delete - removed a wallet o Wallet Identifier and/or Pass Phrase

The IOTP Payment Bridge does not return any information about the set of registered payment instruments because these data items are dynamically inferred during the brand selection process at the beginning of each IOTP transaction. However, the IOTP Application Core has to be notified about new wallets and should be notified about updated and removed wallets (identifier). Alternatively, removed wallets can be implicitly detected during the next brand selection phase. Updated wallets do no affect the processing of the IOTP Application Core. The IOTP Payment Bridge should only support the addition of at most one wallet because it is not able to report multiple additions at once back to the IOTP Application Core.

XML definition:

   <!ELEMENT ManagePaymentSoftwareResponse EMPTY >
   <!ATTLIST ManagePaymentSoftwareResponse
     Action  (New |
      Update |
      Delete)  #IMPLIED
     WalletID  CDATA  #IMPLIED
     Passphrase  CDATA  #IMPLIED
     AuthNames  NMTOKENS  #REQUIRED >

Tables 4 and 5 explain the attributes and elements; Table 3 introduces the Error Codes.

5. Call Back Function

This API function, called by the IOTP Payment Bridge, is used to provide information for Consumer or Payment Handler notification about the progress of the payment transaction.

Its use is illustrated in the diagram below.

   *+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*
                         IOTP Application   ----calls----
                         |     Core     |               |
          display        |              |               v
            to  <----------  Call Back <--calls---  Payment
           user          |              |           Software
                         ----------------
   *+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*+*
                       Figure 9.  Call Back Function

Whenever this function is called, the content of the status description should be made available to the user. For example on a status bar, a pop up window, etc.

A reference to the Call Back function is passed as an input parameter to the "Start Payment X" and "Resume Payment X" API function. Afterwards, this function might be called whenever the status changes or progress needs to be reported.

   Input Parameters
   o  the software identifier of the caller
   o  Party's Payment Identifier
   o  Process State and Percent Complete
   o  Completion Code
   o  Status Description and its language annotation, text which
      provides information about the progress of the call.  It should be
      displayed or made available to, for example, the Consumer.

Examples of Status Description could be:

o "Paying 12.30 USD to XYZ Inc" o "Payment completed" o "Payment aborted"

The valid languages are announced in the Call Back Language List attribute in "Start Payment X" and "Resume Payment X" API function calls.

XML definition:

   <!ELEMENT CallBack EMPTY >
   <!ATTLIST CallBack
     ContentSoftwareID  CDATA  #IMPLIED
     PayId CDATA #REQUIRED
     ProcessState  (NotYetStarted |
      InProgress |
      Suspended |
      CompletedOk |
      Failed |
      ProcessError)  #IMPLIED
     PercentComplete  CDATA  #IMPLIED
     CompletionCode  NMTOKEN  #IMPLIED
     xml:lang  NMTOKEN  #IMPLIED
     StatusDesc  CDATA  #IMPLIED >
   Output Parameters

XML definition:

<!ELEMENT CallBackResponse EMPTY > <!ATTLIST CallBackResponse <!-- see below --> >

Tables 4 and 5 explain the attributes and elements; Table 3 introduces the Error Codes. Basically, the call back function accepts all input arguments or rejects the whole request. It may even accept malformed requests.

Some payment schemes may support or require that the Consumer might be able to cancel the payment at any time. The Call Back function can be used to facilitate this by returning the cancellation request on the next call (using the Business Error Code and Completion Code "ConsCancelled").

Vice versa the Payment Handler's Application Core might use the similar mechanism to signal its IOTP Payment Bridges any exceptional need for a fast shutdown. These IOTP Payment Bridges may initiate the appropriate steps for terminating/cancelling all pending payment transactions.

Note that the "Change Process State" API function provides the second mechanism for such kind of notification. Therefore, the IOTP Payment Bridge or Existing Payment Software may ignore the details of the "Call Back" response.

6. Security Consideration

The IOTP Payment APIs only supports security using pass phrase to access to payment Wallet. These can be protected over TLS, which provides stronger security at the transport layer, but implementations are out the scope of this document.

See also security consideration section of [IOTP].

7. References

7.1. Normative References

   [IOTP]     Burdett, D., "Internet Open Trading Protocol - IOTP
              version 1.0", RFC 2801, April 2000.
   [ISO4217]  ISO 4217: Codes for the Representation of Currencies.
              Available from ANSI or ISO.
   [URL]      Berners-Lee, T., Masinter, L. and M. McCahill, "Uniform
              Resource Locators (URL)", RFC 1738, December 1994.
   [UTC]      Universal Time Coordinated. A method of defining time
              absolutely relative to Greenwich Mean Time (GMT).
              Typically of the form: "CCYY-MM- DDTHH:MM:SS.sssZ+n" where
              the "+n" defines the number of hours from GMT. See ISO
              DIS8601.
   [XML]      Extensible Mark Up Language (XML) 1.0 (Third Edition).  A
              W3C recommendation. See http://www.w3.org/TR/REC-xml
   [XML-NS]   Namespaces in XML Recommendation. T. Bray, D. Hollander,
              A. Layman. Janaury 1999.  http://www.w3.org/TR/REC-xml-
              names
   [XSLT]     Extensible Style Language Transformations 1.0, November
              1999, See http://www.w3.org/TR/xslt

7.2. Informative References

   [IOTPBOOK] D. Burdett, D.E. Eastlake III, and M. Goncalves, Internet
              Open Trading Protocol, McGraw-Hill, 2000. ISBN 0-07-
              135501-4.
   [SET]      SET Secure Electronic Transaction(TM) , Version 1.0, May
              31, 1997
              Book 1: Business Description
              Book 2: Programmer's Guide
              Book 3: Formal Protocol Definition
   [SET/IOTP] Kawatsura, Y., "Secure Electronic Transaction (SET)
              Supplement for the v1.0 Internet Open Trading Protocol
              (IOTP)", RFC 3538, June 2003.
   [TLS]      Dierks, T. and C. Allen, "The TLS Protocol Version 1.0",
              RFC 2246, January 1999.

Acknowledgement

The contributions of Werner Hans of Atos Origin are gratefully acknowledged.

Authors' Addresses

   Hans-Bernhard Beykirch
   EMail: hbbeykirch@web.de
   Yoshiaki Kawatsura
   Hitachi, Ltd.
   890 Kashimada Saiwai-ku Kawasaki-shi
   Kanagawa, Japan 212-8567
   EMail: ykawatsu@itg.hitachi.co.jp
   Masaaki Hiroya
   Technoinfo Service, Inc.
   333-2-718 Uchikoshi-machi
   Hachioji-shi
   Tokyo 192-0911 JAPAN
   EMail: hiroya@st.rim.or.jp

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