ebBP 11/21/2005: BPMN Updates and Discussion

[Monica J Martin <Monica.Martin@Sun.COM>]

As we discussed in Tuesday's call last week, the team wished to review 
in more detail the BPMN v1.0 and draft v1.1 specification, and the 
diagrams as updated. As previously indicated, I had worked with Ugo 
Corda to determine if and how using BPMN we can show how ebBP can map 
the Business Transaction Activity to a series of operations 
(OperationMapping). What is important here and perhaps should be 
considered by BPMN team is there is effectively no mechanism to specify 
a relationship between activity objects unless they are considered a 
subprocess or a transaction or within a pool/lane. Neither of these 
truly represent this use case. There are (at least) two levels of 
specification where we should be able to associate or relate the BTA to 
those operations, each effectively activities in their own right. There 
are some other points to consider regarding differentiating signals from 
business messages, how to accurately show an operation, and what 
objects/lines to use to show responses vs. faults.

Here is a summary of the discussion and potential items to address:

    * Question 1: How to map complex activities to a series of
      operations, where these operations may be associated with or
      related to a BTA? When you choose this particular mapping are you
      in essence combining different process diagrams in the BPMN
      vernacular?

          * It is not an embedded subprocess

        "....An Embedded (or nested) Sub-Process object is an activity
        that contains other activities (a Process). The Process within
        the Process is dependent on the parent Process for instigation
        and has visibility to the parent’s global data. No mapping of
        data is required. The objects within the Embedded Sub-Process,
        being dependent on their parent, do not have all the features of
        a full Business Process Diagram, such as Pools and Lanes. Thus,
        an expanded view of the Embedded Sub-Process would only contain
        Flow Objects, Connecting Objects, and Artifacts....

          * It is not a group (relatively speaking), although it shares
            some characteristics of a group.

        "...A box around a group of objects for documentation
        purposes)....A grouping of activities that does not affect the
        Sequence Flow. The grouping may be used for documentation or
        analytic purposes. Groups can also be used to identify
        activities of a distributed transaction that is shown across Pools."

          * It is not an association (dotted line) although we can
            relate or associate the abstract WSDL operations to BTA
            (Note that the operation is not an artifact, it is in
            essence another flow object).

        "...To satisfy additional modeling concepts that are not part of
        the basic set of flow elements, BPMN provides the concept of
        Artifacts that can be linked to the existing Flow Objects
        through Associations. Thus, Artifacts do not affect the basic
        Sequence or Message Flow, nor do they affect mappings to
        execution languages....An Association is used to associate
        information with Flow Objects. Text and graphical non-Flow
        Objects can be associated with the Flow Objects...."

    * Question 2: What gateway control type is appropriate when you
      actually could have -n- potential paths on a fork or join, and
      either only one is actually performed or many could be performed,
      and business messages are sent? This is actually a conceptual
      difference in current BPMN v1.0 and collaboration whereby not all
      paths may be rendered executable or be used in execution
      (monitorable in ebBP context).
          o The BPMN team had questioned why we used an exclusive/or
            rather than inclusive/or gateway (See Section 3.2 objects)
            when we could have multiple input or output from a fork or
            join. This is represented in a gateway in BPMN. The
            inclusive/or gateway with the message flow is not allowed in
            BPMN.
          o The BPMN team had questioned why we needed to have multiple
            messages as input to or output from a gateway (which is not
            allowed in BPMN).

        Instead of using an exclusive/or gateway with multiple message
        flows into or out of an exclusive/or gateway, I updated the
        diagrams to show an inclusive/or with sequence flows to
        intermediate messages to show that one actual Response on the
        Responding Business Activity results. See v2.0.1 CD and v2.0.1
        PR diagram changes to visually represent this discussion. Please
        also review BPMN Section 4.5 that talks about exclusive/or
        gateway and how condition expressions are used (XPath based for
        example) to effect what path(s) is/are taken. It appears that an
        exclusive/or gateway could be used but the assumptions are
        different (shows sequence rather than the potential flow of
        business messages which may suit our needs).

    * Question 3: Differentiating business messages and/or business
      signals: As allowable extensions, I have differentiated business
      messages from business signals (blue and green respectively for
      color, and used a heavier weight line). The BPMN team may consider
      that this differentiation is important for intentional collaboration.
    * Question 4 (related to Question 1) : When you have a complex
      activity that may be mapped multiple operations, how do you
      represent the fact that an abstract WSDL operation could have the
      Response or a fault(s)? See our updated Figure 8.

Diagrams I've included:

   1. Diagrams as specified in v2.0.1 Committee Draft (2 diagrams)
          * Requesting and Responding Business Activity on a typical
            Commercial Transaction pattern.
          * Requesting and Responding Business Activity on a typical
            Commercial Transaction pattern using Operation Mapping.
   2. Diagrams updated given comments from BPMN team for v2.0.1 Public
      Review draft candidate (2 diagrams)
          * Requesting and Responding Business Activity on a typical
            Commercial Transaction pattern.
          * Requesting and Responding Business Activity on a typical
            Commercial Transaction pattern using Operation Mapping.

Relevant references:

    * Updated ebBP diagrams -
      http://www.oasis-open.org/apps/org/workgroup/ebxml-bp/email/archives/200511/msg00035.html
      (14 November 2005)
          o All diagrams uploaded to ebBP site for ease of accessibility:
                + (TC)
                  http://www.oasis-open.org/apps/org/workgroup/ebxml-bp/document.php?document_id=15368
                + (public)
                  http://www.oasis-open.org/committees/document.php?document_id=15368&wg_abbrev=ebxml-bp

            Note. The file (.zzz) needs to be renamed to a (.zip) to
            open and view the four diagrams.

    * BPMN v1.0:
      http://www.bpmn.org/Documents/BPMN%20V1-0%20May%203%202004.pdf
    * BPMN v1.1 (draft): http://www.bpmn.org/Documents/BPMN%201-X.pdf

Finally, Stephen and Ugo, I'd like to log these as questions to the BPMN 
team for future consideration as appropriate. Thanks.