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RE: Grounding Choreographies (the atoms) - WAS Simple Choreography composition suggestion

From: Martin Chapman <martin.chapman@oracle.com>
Date: Thu, 17 Jul 2003 10:53:02 -0700
To: "Francis McCabe" <fgm@fla.fujitsu.com>
Cc: "Steve Ross-Talbot" <steve@enigmatec.net>, "Champion, Mike" <Mike.Champion@SoftwareAG-USA.com>, <public-ws-chor@w3.org>
Message-ID: <PEEBJKKCFNCENDPJDEMIKEFMDHAA.martin.chapman@oracle.com>

even though we don't have agree teminology yet perhaps we sould start using
the term agent
instead of party or participant.

martin.

> -----Original Message-----
> From: public-ws-chor-request@w3.org
> [mailto:public-ws-chor-request@w3.org]On Behalf Of Francis McCabe
> Sent: Thursday, July 17, 2003 10:30 AM
> To: Martin Chapman
> Cc: Steve Ross-Talbot; Champion, Mike; public-ws-chor@w3.org
> Subject: Re: Grounding Choreographies (the atoms) - WAS Simple
> Choreography composition suggestion
>
>
>
> +1.
>
> Following the form of the WSA, we have agents that provide and request
> Web services. This is based on the intuition that a service is
> fundamentally about the potential for action, and that actors
> (computational and otherwise) are the entities that do the acting.
>
> Frank
>
> On Thursday, July 17, 2003, at 09:16  AM, Martin Chapman wrote:
>
> >
> > I think there is a fundamental terminology issue here that needs to be
> > cleared up.
> > An entity (avoiding any overloaded word) that sends a message to a web
> > service (and may expect a response depending on the wsdl) doesn not
> > iteslf
> > have to be a web service. This is the most fundamental building block.
> > Furthermore this interaction supports an MEP (in soap teminology) and
> > pattern (in wsd teminology).
> > Perosnllay if we can not describe these meps in a choreography
> > language we
> > have failed, and hence I do not think that mep choreogaprhy is any
> > different
> > from web service choreography.
> >
> > Martin.
> >
> >
> >
> >> -----Original Message-----
> >> From: public-ws-chor-request@w3.org
> >> [mailto:public-ws-chor-request@w3.org]On Behalf Of Steve Ross-Talbot
> >> Sent: Thursday, July 17, 2003 2:14 AM
> >> To: Champion, Mike
> >> Cc: public-ws-chor@w3.org
> >> Subject: Grounding Choreographies (the atoms) - WAS Simple
> >> Choreography
> >> composition suggestion
> >>
> >>
> >>
> >>    At the considerable risk of adding further confusion to the
> >> discussion I would like to attempt to clarify what I said on the call
> >> with respect to the grounding of a choroegraphy.
> >>
> >>
> >>    Here is how I see it:
> >>
> >>    A "web service" choreography, as distinct from any other
> >> choreography, is grounded to a minimum of two web services instances.
> >> This may mean that the web services are the same web services but
> >> different instance or it may mean that they are distinct (personally I
> >> have a hard time seeing what they would be anything other than the
> >> latter) such that I can observe a communication between them.
> >>
> >>    A communication is a minimum of a single message sent from one web
> >> service to another web service.
> >
> >
> >
> >>
> >>    It may be the case that in receiving or indeed sending a message
> >> the
> >> sending web service and/or the receiving web service can be externally
> >> observed to change their behaviour.
> >>
> >>    A "web service" choreography, as distinct from any other
> >> choreography, is based on externally observable behaviour where this
> >> behaviour is defined in terms of communications between web services
> >> and externally observed behavioral changes of a web service.
> >>
> >>    For the avoidance of doubt, a Message Exchange Pattern (MEP) or any
> >> mechanism that describes communication between two parties can be said
> >> to be a choreography. But it cannot be said to be a "web service"
> >> choreography.
> >>
> >>
> >> Cheers
> >>
> >> Steve T
> >>
> >>
> >> On Wednesday, July 16, 2003, at 02:57  pm, Champion, Mike wrote:
> >>
> >>>
> >>>
> >>>
> >>>> -----Original Message-----
> >>>> From: Fletcher, Tony [mailto:Tony.Fletcher@choreology.com]
> >>>> Sent: Wednesday, July 16, 2003 9:12 AM
> >>>> To: public-ws-chor@w3.org
> >>>> Subject: FW: Simple Choreography composition suggestion
> >>>>
> >>>
> >>>>
> >>>> The point I disagree with is the notion that something is not a
> >>>> Choreography if somewhere, at some level it involves 'orchestration'
> >>>> within a single system.  If we accept this notion /
> >>>> restriction it means
> >>>> that you can only have Choreographies involving exactly two parties
> >>>> where each party only plays a single role - we will not be
> >>>> able to have
> >>>> Choreographies with more than two parties / roles at all.
> >>>
> >>> That wasn't my intent, FWIW.  All sorts of compositions and
> >>> decompositions
> >>> can occur within a "choreography," but IMHO only those that involve
> >>> the
> >>> globally visible shared state are in scope for the choreography
> >>> description
> >>> language we are developing.  The discussion yesterday got me
> >>> re-thinking all
> >>> sorts of things ... if the fundamental unit of a "choreography" is a
> >>> Web
> >>> service invocation / MEP, then all sorts of implementation details of
> >>> the
> >>> service that involved "orchestrated" interactions behind the scenes
> >>> are
> >>> abstracted away, but if the fundamental unit is a message, then all
> >>> those
> >>> messages behind the scenes have to be accounted for somehow.  I'm as
> >>> confused as anyone at this point.
> >>>
> >>> By all means let's make sure that we don't box ourselves into a
> >>> corner
> >>> based
> >>> on some preliminary guesses about what terms mean!
> >>>
> >>>
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>
>
Received on Thursday, 17 July 2003 13:52:51 GMT

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