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Date: Thu, 28 Jun 2007 12:54:48 -0400
From: "Rahul Akolkar" <rahul.akolkar@gmail.com>
To: "Jakarta Commons Users List" <commons-user@jakarta.apache.org>
Subject: Re: [SCXML] Querying if an event would cause a transition
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On 6/28/07, Nestor Urquiza <nestoru@yahoo.com> wrote:
> Hi,
>
> Not to mention that some custom actions could have to be evaluated before knowing which transition will apply.
>
> It might mean that some side effects could come into scene, and if they do  the "introspection mode" cannot be used.
>
<snip/>

Actions aren't executed unless a transition is actually followed, so
we should be OK there. However, the guard conditions on candidate
transitions would need to be evaluated, and they would need to be
side-effect free (as they should be).

In other words, the act of identifying which transition(s) should be
followed is idempotent.

-Rahul


> Thanks,
>
> -Nestor
>
> ----- Original Message ----
> From: Rahul Akolkar <rahul.akolkar@gmail.com>
> To: Jakarta Commons Users List <commons-user@jakarta.apache.org>
> Sent: Wednesday, June 27, 2007 11:05:54 AM
> Subject: Re: [SCXML] Querying if an event would cause a transition
>
> Please prefix the email subject with [SCXML], since this mailing list
> is shared across all Commons components. I've added the prefix here.
>
> On 6/27/07, Christopher Giblin <CGI@zurich.ibm.com> wrote:
> >
> > Hi,
> > I am new to Commons SCXML.
> > Is it possible to determine whether an event would result in a transition,
> > without that transition occuring? Including evaluation of transition
> > conditions?
> <snip/>
>
> While the idea is interesting, we do not have such an "introspection mode".
>
> It wouldn't take too much effort to implement it, but:
>
> a) Would probably increase the code smell factor a tad (if in
> introspection mode, then follow transition else just report back etc.)
>
> b) Would require some API additions that might warrant a major release.
>
> If you don't mind sharing in this public forum, why do you need such
> introspection? The SCXML specification doesn't talk about this.
> Understanding that interaction pattern may or may not help better
> answer the question, we will have to see :-)
>
> -Rahul
>
>
> > Thanks,
> > chris
> >
> >

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