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RE: SCXML : Event Generation and Dynamic Creation of Statechart

From: Barnett, James <James.Barnett@Aspect.com>
Date: Thu, 13 Apr 2006 09:57:29 -0400
Message-ID: <CDB88C76D4D72244973F442A5305F0F95587C2@BOS1EXCH1.aspect.com>
To: <raxit@phonologies.com>, <www-voice@w3.org>, <bond@research.att.com>

Raxit,
  Dynamic creation of states is something that we have consciously ruled
out for SCXML.  The basic idea of state machines is that they have a
fixed set of states. Even push-down automata, which are more powerful
than finite state machines, have a fixed set of states, plus a dynamic
stack.  

One strong advantage of having a fixed set of states is that machines
are statically analyzable - by looking at chains of transitions, you can
determine whether there is a path from any given state to any other
state.  

We therefore do not want any constructs in SCXML that involve the
dynamic creation of states.  There is a way of handling multiple
<invoke> at the platform layer that does not have this problem, and we
will post a message on this topic soon.  

- Jim


-----Original Message-----
From: Sheth Raxit [mailto:raxit@phonologies.com] 
Sent: Monday, April 10, 2006 2:05 AM
To: www-voice@w3.org; Barnett, James; bond@research.att.com;
Alfred.S.Gilman@IEEE.org
Subject: SCXML : Event Generation and Dynamic Creation of Statechart

Respected  James,Greg,Gilman and other VBVG Members,

With reference to previous posts, One of the point is to Generate Event 
and related stuff while processing <invoke>, I think that this is 
somewhat  like (or can be modeled as)  what  Greg has mentioned ( in 
this post 
http://lists.w3.org/Archives/Public/www-voice/2006JanMar/0040.html ),  
issue ,"Dynamic Creation of Statecharts".

I think (but not much sure )that <invoke> can be modeled as , Dynamic 
Creation of new State (with new State-Id) and call to appropriate 
services, and as  actuall call is madeup from new state, with new 
stateid, What Gilman has suggested the concepts of Event would now apply

to this New-State, and this new-state now would do all the event 
handling and related stuff.

when SCXML Engine hits <invoke>
1. Dynamically Create new state, (with unique State Id)
2. Make appropriate stuff to call Service,
3. Call the Service,
4. Do Event Handling for the Events arrived from services,


Would it  be Semantically equivalent of Event-related stuff (suggested 
by Gilman),  ?

Any thought on this issue ?


Thanks,
---
Raxit Sheth

-- 

Raxit Sheth
Systems Software Engineer
Raxit@Phonologies.com

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Received on Thursday, 13 April 2006 13:56:26 GMT

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