Re-usable Guards for State Transitions

Chandon,

Lacking insight into your organization's model standards and conventions (yes, I think this case should be documented there), I'll suggest you consider modeling a Constraint (std, not a constraint block) using OCL and linking your recurring state machine Guards to the Constraint. Hopefully your tooling supports model simulation when using OCL for this purpose.

Regards,
Geoff

In reply to Geoffrey Shuebrook:

Hi Geoff, thanks for the suggestion.  I tried this and I am able to point a transition to a constraint (owned by the state machine's classifier), but that creates a copy of the original constraint under the transition. 

If i am interpreting UML spec correctly (v2.5.1, section 14.2.2), it appears that a guard (as constraint) can be owned by up to one transition, so the language may not support the exact feature I'm looking for.

Respectfully,

Chandan

In reply to Chandan Mathur:

I forgot to mention - I can drag/drop a constraint onto a transition and that will create a constraint on the transition, but that constraint is not set as the guard.

In reply to Chandan Mathur:

Chandon,

Apologies.

Re: UML v2.5.1, section 14.2.2 (not being argumentative) as I read the Abstract Specification of a Transition, a Transition may have an optional property named "guard" which is of type Constraint, which is further constrained to a single Constraint specification if present (multiplicity = 0..1). I make no claim to being a UML expert and may interpretation is based solely on my independent study of the language. I may be wrong. This is my understanding and I do not intend to argue the point, but I am willing to correct my understanding with inout from an expert.

I played around with CSM 19.4 this morning trying both OCL for the Guard and an "Opaque Expression". While I still believe that the Constraint model element is appropriate, I concur the behavior of the tool may be a suboptimal solution.

Another approach: Consider specifying your complex Guard expression in the form of an Opaque Expression. In my experimentation, I created a separate package containing the named opaque expression ( I named the expression as the hyperlinking dialog lists model elements by their name). Then from the specification of the Transition's Guard property, I hyperlinked to the Body ("Representation Text") of the Named Opaque Expression. I did this for multiple transitions of the State Machine. Further I made a change to the Opaque Expression and the change was reflected in the Guard of all the linked Transitions.

If this isn't the solution your desire, I apologize. Best of Luck.

Regards,
Geoff

In reply to Geoffrey Shuebrook:

Geoff, very much appreciate your advice and thanks for your suggestion on the opaque expression...I will give that a try. I think that will meet my needs.

Respectfully,

Chandan