Issue 7254: completion transitions (uml2-rtf)
Source:  (, )
Nature: Clarification
Severity: Minor
Summary: Suppose that we have two composite states, nested within to two concurrent regions, which both become "complete" as part of the same "run-to-completion" step, and each of the composite states is the source for a completion transition. I.e. within this "run-to-completion" step two completion events are generated. How should these two completion events be dispatched? - Sequentially, in the same sequential order in which they have been generated. - Sequentially, but any ordering is allowed, - Concurrently. I.e. both completion transitions are considered enabled. - other ??? or any of the above Notice that completion transition may have guards, and activity, hence the firing of one of them may cause the other to become no more "enabled". Hence the above three cases may really cause different system behaviors. 

Resolution: Add a clarification for this case based on the above discussion
Revised Text: In clause 14.2.3, mmediately following this sentence:
That is, they are dispatched ahead of any pending Event occurrences in the event pool.
insert the following clarification:
If two or more completion events corresponding to multiple orthogonal Regions occur simultaneously (i.e.,
as a result of the same Event occurrence), the order in which such completion occurrences are processed is
not defined.
Actions taken:
April 21, 2004: received issue
February 20, 2015: closed issue
Discussion: 
In general, the order of dispatching of event occurrences in UML is not specified, allowing it to be customized
for different cases. However, completion events for state machines are given priority over other
types of event occurrences, meaning that they are dispatched ahead of any other occurrences. It is indeed
possible for multiple completion events to occur “simultaneously”, which creates the quandary described in
the issue.
But, given that there is no formal means of ordering the generation of such events or even defining the “order”
of the corresponding regions, there is no meaningful basis for ordering the dispatching of simultaneous
completion events. Hence, this will have to remain unspecified. (NB: This is analogous to and consistent
with the case where multiple transitions can be enabled by a given event occurrence.)
End of Annotations:=====
From: webmaster@omg.org 
Date: 21 Apr 2004 10:16:19 -0400 
To: <issues@omg.org> 
Subject: Issue/Bug Report 



--------------------------------------------------------------------------------

Name: Franco Mazzanti
Company: ISTI-CNR
mailFrom: mazzanti@isti.cnr.it
Notification: Yes
Specification: UML 2.0 Superstructure Specification
Section: 15.3.12
FormalNumber: ptc
Version: 03-08-02
RevisionDate: 08/02/2003
Page: 500
Nature: Clarification
Severity: Minor
HTTP User Agent: Mozilla/5.0 (Macintosh; U; PPC Mac OS X Mach-O; en-US; rv:1.6) Gecko/20040206 Firefox/0.8
Description
Suppose that we have two composite states, nested within to two concurrent regions, which both become "complete" as part of the same "run-to-completion" step, and each of the composite states is the source for a completion transition. I.e. within this "run-to-completion" step two completion events are generated. How should these two completion events be dispatched? - Sequentially, in the same sequential order in which they have been generated. - Sequentially, but any ordering is allowed, - Concurrently. I.e. both completion transitions are considered enabled. - other ??? or any of the above Notice that completion transition may have guards, and activity, hence the firing of one of them may cause the other to become no more "enabled". Hence the above three cases may really cause different system behaviors.