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  1. OMG Issue

BPMN21 — BPMN 2.0 Choreography issues page 327 of dtc/2010-06-05

  • Key: BPMN21-306
  • Legacy Issue Number: 16547
  • Status: open  
  • Source: Anonymous
  • Summary:

    Page 327 of /dtc/2010-06-05/ runs as follows (emphasis in the last
    sentence added):

    “To leverage the familiarity of flow charting types of Process
    models, BPMN Choreographies also have “activities” that are ordered
    by Sequence Flows. These “activities” consist of one (1) or more
    interactions between Participants. These interactions are often
    described as being message exchange patterns (MEPs). A MEP is the
    atomic unit (“Activity”) of a Choreography.

    Some MEPs involve a single Message (e.g., a “Customer” requests an
    “Order” from a “Supplier”). Other MEPs will involve two (2) Messages
    in a request and response format (e.g., a “Supplier” request a
    “Credit Rating” from a “Financial Institution,” who then returns the
    “Credit Rating” to the “Supplier”). There can be even more complex
    MEPs that involve error Messages, for example.”

    This wording may result confusing to practitioners. First of all,
    there is no way in BPMN 2.0 Choreographies to mark a message as an
    “error message”. What the specification seems to hint at is that
    some of the messages in the choreography may deliver information
    over errors. However, since BPMN 2.0 Choreographies (and, more
    generally, BPMN 2.0 as a whole) does not differentiate among the
    possible “typologies” of messages (e.g. error, acknowledgement,
    invocation, or response), there is no immediate way to map WSDL
    1.1/2.0 MEPs to single Choreography Taskswithout losing some
    information (e.g. the distinction between output messages and fault
    messages). Even using the structureRefof the message(see e.g. Page 7
    of /dtc/2010-06-05/) to point to a WSDL 1.1/2.0 message, this would
    provide no information about what “type” of message it is. In fact,
    in WSDL 1.1/2.0 a message is “labelled” as input, output or fault
    only in the WSDL operations, so much that a given WSDL message
    could, for example, be input in one operation and a fault in another.

    Secondly, despite the fact that the text mentions Choreography
    Activities as the realization of MEPs (i.e. also
    Sub-choreographies), the reference to MEPs as atomic units sounds
    intuitively related to Choreography Tasks. Given the fact that it is
    not possible to (1) specify error messages and (2) specify the
    sequencing in a single Choreography Taskfor more than two messages,
    a single Choreography Taskallows the specification of only the WSDL
    1.1 “one-way messaging” and “notification” MEPs. In fact, the
    specification of “request/reply” and “solicit/response” MEPs is not
    possible because their faults cannot be represented in the same
    Choreography Tasktogether with the input and output messages.

    To clarify this issues, the specification should address clearly and
    in detail the relation between BPMN 2.0 Choreographies and MEPs in
    WSDL 1.1 and WSDL 2.0, in particular with relation to the
    granularity of the MEPs (Choreography Task-level, Sub-choreography
    level, etc.). Moreover, it is still an open issue how to map WSDL
    2.0 Complex MEPs to BPMN 2.0 Choreographies.

  • Reported: BPMN 2.0 — Wed, 14 Sep 2011 04:00 GMT
  • Updated: Fri, 6 Mar 2015 20:57 GMT