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From Nestor Urquiza <>
Subject Re: [SCXML] Event types
Date Tue, 29 May 2007 18:42:24 GMT
As always Thanks a lot Rahul for your clarifications.


----- Original Message ----
From: Rahul Akolkar <>
To: Jakarta Commons Users List <>
Sent: Monday, May 28, 2007 10:23:05 PM
Subject: Re: [SCXML] Event types

On 5/28/07, Nestor Urquiza <> wrote:
> <snip>
> Bits like <invoke>, are also "executable content", but the semantics
> are decoupled from the mechanics of state transitions.
> </snip>
> As far as I understand <invoke> is still an ongoing discussion from w3c draft right?
I mean it is not clear still how invoke will accept parameters and how the result would be
processed by the <onentry> or <onexit> contexts from where at the end of the row
<invoke> will be used.

Correct, <invoke> has many details TBD. Results are processed in <finalize>.

> In any case even using invoke I do not see an alternative to <if> when talking
about exceptions, meaning that seems like the approach I am finaly using is the only practical
solution for WEB domain. Basically I call custom actions from <var> and I check for
the returned value.

Yup, its a viable solution ATM.

> <snip>
> Discussions on priority are useful in event queues (prior to the point
> any event is being processed by the engine). In processing events, the
> state machine uses one or more events (immutable set) in every "step"
> (and any derived events get added to the front of the queue).
> </snip>
> I get it, priority should be used just to control which events will be executed before
and which after but never as a mean of stopping the  precessing of  any other event. Also
exeptions are not a way to go  IMO when using expression languages as SCXML does so far. Simply
very basic structured programming is to be used there, and I say very basic since we have
no serious thinking from w3c side to include ECMA scripting within <script> or as part
of some code to be executed by <invoke> as a possible full featured programming language
that will for example allow reuse (I am doing reuse using XML entities which has several disadvantages
already posted in previous posts here and at www voice w3c forum).

Your feedback is appreciated here (as I'm sure it is on the other list).


> Thanks,
> -Nestor

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