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  1. OMG Issue

BPMN21 — Link Events - Constraints and Usage not clearly documented

  • Key: BPMN21-63
  • Legacy Issue Number: 14815
  • Status: open  
  • Source: International Business Machines ( Ms. Suzette Samoojh)
  • Summary:

    The Sequence Flow constraints around the usage of Link Events are not clearly expressed in the spec.

    Very simply, it should express that:

    • A Catch Link Event should have no incoming Sequence Flow.
    • A Throw Link Event should have no outgoing Sequence Flow.

    Instead the spec has several rather confusing statements (pgs 235-236) that make it hard to infer the simple behavior I described above.
    Statements like:

    • If the Intermediate Event is used within normal flow:
    • Intermediate Events MUST be the target of a Sequence Flow.
    • An Intermediate Event MUST be a source for Sequence Flow.
    • An exception to this: a source Link Intermediate Event (as defined below), it is not required to have an outgoing Sequence Flow.
    • A Link Intermediate Event MUST NOT be both a target and a source of a Sequence Flow.
    • A Link Intermediate Event MAY be the target (target Link) or a source (source Link) of a Sequence Flow, but MUST NOT be both a target and a source.


    • Tighten up and simplify the constraint descriptions for Link Events.
    • Refrain from introducing new terms "source" and "target", or if the new terms are needed, clearly relate them to the existing "catch" and "throw" terms.
  • Reported: BPMN 2.0b1 — Mon, 23 Nov 2009 05:00 GMT
  • Updated: Fri, 6 Mar 2015 20:57 GMT