<quote>
* Check before and after status of executor while firing events, and
fire an "application.default" event if the trigger is inconsequential
(can do this with current nightlies)
</quote>
I dont think that this is gonna work, I can actually want to be in the same
state, in which case, I would add a no action transition. However the idea
of firing something like transition.inconsequential was neat (StateEngine
would know exactly that there is no transition, not even a dummy one). I
will use the latest nightlies.
+Fasih
----- Original Message -----
From: "Rahul Akolkar" <[EMAIL PROTECTED]>
To: "Jakarta Commons Users List" <[email protected]>
Sent: Saturday, April 08, 2006 12:53 PM
Subject: Re: [SCXML] Default Transitions
On 4/8/06, Fasih <[EMAIL PROTECTED]> wrote:
Hmm... That src idea was cool. Though I find the superstate concept
better.
<snip/>
Sure, its a matter of style, in fact the "superstate" is much
easier/efficient for the parsing bits. The end effect is usually the
same if you squint at it long enough though ;-)
I can easily do
<state id="setup-call">
<initial>
<transition target="create-call"/>
</initial>
<state id="create-call">
<onentry>
<ccxml:createcall dest="accessnumber" name="line1"/>
</onentry>
<transition event="connection.connected" target="waiting-for-ivr"/>
</state>
...
<!-- Here, though I would have loved to do a event="*" types of a usage..
that is, any event not handled by a substate, does not look like that it
would be possible/-->
<snap/>
There is no elegant construct for this in SCXML. Indeed, it is not
possible to graphically represent this transition in most UML tooling,
nor does such a concept exist in greater state chart theory, AFAIK.
There is no premise that an event *must* cause something to happen,
and it is perfectly acceptable to have an event do nothing to a state
machine's current status (I call these inconsequential events).
In order to get what you need here, there are multiple options (not a
complete list):
* Complementary conds on transitions (ugly hack, not scalable)
* Check before and after status of executor while firing events, and
fire an "application.default" event if the trigger is inconsequential
(can do this with current nightlies)
* We should modify the SCXMLExecutor's triggerEvent() method itself
to offer this feedback, so the tedium of checking the before/after
status will be eliminated. To the effect of:
<pseudo>
boolean inconsequential = exec.triggerEvent(...);
if (inconsequential) {
exec.triggerEvent(defaultEvent);
} else {
//optionally, do something else
}
</pseudo>
This approach was used here [1], though I never got around to pushing
it into the nightlies.
<transition event="connection.failed" target="error"/>
</state>
<state id="error" final="true">
...
</state>
</scxml>
Instead of putting a src on each of the state to do the error transition??
(i.e. If I am not wrong in understanding the concept!)
<snip/>
Lets say we have a state machine defined via a SCXML document
inner.scxml. To add a candidate transition across the board for this
state machine, we would do:
outer.scxml:
<scxml ... initialstate="inner">
<state id="inner" src="inner.scxml">
<transition event="application.error" target="error"/>
</state>
<state id="error" final="true"/>
</scxml>
HTH,
-Rahul
[1] http://people.apache.org/~rahul/shale/dialog-delegation/
+Fasih
<snip/>
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