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From "Rahul Akolkar" <rahul.akol...@gmail.com>
Subject Re: [SCXML] Event types
Date Tue, 22 May 2007 19:47:17 GMT
On 5/22/07, Nestor Urquiza <nestoru@yahoo.com> wrote:
> So you mean commons-scxml users should provide their application specific SCXMLSemanticImpl.java?
Which method should we use to use a custom one that lives in a different than org.apache.commons.scxml.semantics
package?
>
<snip/>

No (well, depends on the specifics but that wouldn't be the first
course of action -- since that deviates from what is provided out of
the box).

To answer the other question, IIUC -- if custom SCXMLSemantics are
indeed defined, then the four argument SCXMLExecutor constructor needs
to be used.

I meant to say that event names (such as "app.error" in your example,
which should be called "error.app" IMO to better serve an event
ontology when using wild cards etc.), event types (trickier to get at)
and event payloads etc. often make more sense to the application
(rather than the library).

-Rahul


> Thanks,
>
> -Nestor
>
> ----- Original Message ----
> From: Rahul Akolkar <rahul.akolkar@gmail.com>
> To: Jakarta Commons Users List <commons-user@jakarta.apache.org>
> Sent: Monday, May 21, 2007 10:58:29 PM
> Subject: Re: [SCXML] Event types
>
> On 5/21/07, Nestor Urquiza <nestoru@yahoo.com> wrote:
> > Hi Rahul,
> >
> > Talking about this I do not know if I posted about it before ( lazy now to search
in the archives ) but at some point I ( at least ) thought about a special event let us say
"app.error" that I was hoping to use from a custom action for example to provide an "exception"
mechanism.
> >
> > In a glance imagine your custom action needs to stop the normal course of your SCXML
code. I was hoping to use the type ERROR to define a special event called "app.error" that
would be included in the transition element to specify where to go when an unexpected exception
occurs.
> >
> > My guess a while ago was that it would be great to make commons-SCXML "exception
aware" meaning that if for some reason an event of ERROR type is raised the complete state
machine would stop processing the current logic triggerred by a regular event and would then
proceed to the transitions to move the FSM to a state corresponding to the error event transition
target.
> >
> > Makes sense?
> >
> <snip/>
>
> Yes, users can leverage the event types (either existing or new /
> user-defined) to have application-specific semantics, as you indicate
> above. However, Commons SCXML itself does not use the type
> information.
>
> -Rahul
>
>
> > Thanks,
> >
> > -Nestor
> >
> > ----- Original Message ----
> > From: Rahul Akolkar <rahul.akolkar@gmail.com>
> > To: Jakarta Commons Users List <commons-user@jakarta.apache.org>
> > Sent: Monday, May 21, 2007 1:06:18 PM
> > Subject: Re: [SCXML] Event types
> >
> > On 5/20/07, Hanh-Missi Tran <Missi.Tran-han@lifl.fr> wrote:
> > > Hi
> > >
> > > A TriggerEvent object is associated with a type (CALL_EVENT,
> > > SIGNAL_EVENT, ..) but   I don't know what they are used for. I look in
> > > the source code but whenever an event is handled, its type is not used
> > > (I'm wrong ?). So can someone tell me what they may be used for ?
> > >
> > <snip/>
> >
> > You are correct, the type information is not used.
> >
> > One of the intents of providing that was to use it as potential basis
> > for priority (for example, a CHANGE_EVENT, since its usually a derived
> > event, would have a lower priority etc.) -- but that was never
> > realized in code (or spec).
> >
> > -Rahul
> >

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