Re: ActivityEdge semantics

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From: Les Munday (
Date: Mon 08 Sep 2003 - 18:55:36 BST

I don't know the answer to this, but if it's ambiguous then I
would not use it.

I am of the understanding that a decision fork may be joined by
having both paths converge on a single activity, instead of
using a decision box to merge the paths.

This would be consistent with creating a decision split with two
paths exiting the same activity.

If this is chanig in UML 2.0, it going to make life very
confusing and create a lot of re-work for existing UML


P.S. Hope you don't mind if I copy this and post to the Rational
UML users group.

Get your own "800" number
Voicemail, fax, email, and a lot more

---- On Mon, 8 Sep 2003, John Daniels (

> Dear UMLers,
> I have a question about the semantics of multiple transitions
> leaving an action in an activity diagram.
> In UML 1.5, drawing an action with multiple outgoing
> implied a decision point, as explained in the spec:
> ----
> A decision may be shown by labeling multiple output
> transitions of an action with different guard conditions.
> ----
> However, my brief reading of the UML 2 "final draft"
> spec seems to suggest that the meaning has changed:
> ----
> [4] When completed, an action execution offers object tokens
on all
> its output pins and control tokens on all its outgoing control
> (implicit fork), and it terminates. Exceptions to this are
> below. The output tokens are now available to satisfy the
control or
> object flow prerequisites for other action executions.
> ----
> I take this to mean that drawing multiple outgoing
"transitions" from
> an action in UML 2 implies forking, not decision branching. Am
> right?
> All the best,
> --John
> John Daniels
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