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RE: Events and States (was: timeouts & states (was: Abstract Bind able Choreography))

From: Cummins, Fred A <fred.cummins@eds.com>
Date: Thu, 10 Apr 2003 19:38:15 -0500
Message-ID: <27C20ED5A6D3D511ADF30002A5D6464802A7146B@USPLM214>
To: Assaf Arkin <arkin@intalio.com>, "Burdett, David" <david.burdett@commerceone.com>
Cc: "'jdart@tibco.com'" <jdart@tibco.com>, public-ws-chor@w3.org

David,

I'm not sure why I haven't received your message directly, but
I like your linkage of state machine to process functionality.
This provides a clean separation of the external choreography
from the internal process.  We can then focus on how messages
are exchanged between participants according to the state 
transitions of their public state machines.

Fred

> -----Original Message-----
> From: Assaf Arkin [mailto:arkin@intalio.com]
> Sent: Thursday, April 10, 2003 7:17 PM
> To: Burdett, David
> Cc: 'jdart@tibco.com'; Cummins, Fred A; public-ws-chor@w3.org
> Subject: Re: Events and States (was: timeouts & states (was: Abstract
> Bind able Choreography))
> 
> 
> +1
> 
> arkin
> 
> Burdett, David wrote:
> 
> > >>>Very good questions. But what do you want (or perhaps more 
> > importantly,
> > need) it to do? As you say, a state machine is really a 
> mechanism. What
> > is the functional requirement?<<<
> >
> > I would put the functional requirements for which state 
> machines are a 
> > possible answer as follows:
> >
> > "An implementation of a process that is following a 
> choreography MUST 
> > be able to verify that the choreography is being followed 
> correctly as 
> > specified in the choreography definition."
> >
> > I would then have two further more closely defined but related 
> > requirements of the products of this group ...
> >
> > "A choreography definition should be usable at Design Time 
> to validate 
> > that a process should be capable of carrying out a choreography 
> > correctly as specified."
> >
> > "A choreography definition shoule be usable at Run Time to validate 
> > that a process is executing a choreography correctly as specified".
> >
> > ... and finally one more ...
> >
> > "If a process detects that a choreography is not being followed 
> > correctly, then the process SHOULD be able to use the choreography 
> > definition to identify exactly what went wrong."
> >
> > This last one means that you stand a better chance of being able to 
> > fix the problem when it occurs.
> >
> > Thoughts?
> >
> > David
> >
> >
> > -----Original Message-----
> > From: Jon Dart [mailto:jdart@tibco.com]
> > Sent: Thursday, April 10, 2003 2:56 PM
> > To: Cummins Fred A
> > Cc: public-ws-chor@w3.org
> > Subject: Re: Events and States (was: timeouts & states 
> (was: Abstract
> > Bindable Choreography))
> >
> >
> >
> > Cummins, Fred A wrote:
> > > This raises questions about the scope of a choreography.  
> When does
> > > it end?  When a disconnect occurs?  When a particular business
> > > transaction is completed?  When a relationship is terminated?
> > > Maybe any of the above?
> > >
> > > Do the state machines provide the mechanism for nesting 
> of component
> > > choreographies?
> >
> > Very good questions. But what do you want (or perhaps more 
> importantly,
> > need) it to do? As you say, a state machine is really a 
> mechanism. What
> > is the functional requirement?
> >
> > At minimum, I would guess it is the ability to transition 
> to a distinct
> > state when a timeout occurs. This state could be the 
> termination of the
> > choreography (implying no more processing will occur). Or 
> it could be an
> > error state (implying there might be some warning given, or some
> > recovery effort made, e.g. a retry - this assumes you are 
> doing this at
> > the application level and not in some lower-level reliable messaging
> > protocol). Certainly I can think of real-world examples 
> where you'd need
> > this functionality. This is something of a simplification of earlier
> > proposals. If we need something more complex, I'd like to see some
> > rationale behind it.
> >
> > --Jon
> >
> 
> 
> -- 
> "Those who can, do; those who can't, make screenshots"
> 
> ----------------------------------------------------------------------
> Assaf Arkin                                          arkin@intalio.com
> Intalio Inc.                                           www.intalio.com
> The Business Process Management Company                 (650) 577 4700
> 
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Received on Thursday, 10 April 2003 20:38:23 UTC

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