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

From: Francis McCabe <fgm@fla.fujitsu.com>
Date: Thu, 17 Jul 2003 10:30:22 -0700
Cc: "Steve Ross-Talbot" <steve@enigmatec.net>, "Champion, Mike" <Mike.Champion@SoftwareAG-USA.com>, <public-ws-chor@w3.org>
To: "Martin Chapman" <martin.chapman@oracle.com>
Message-Id: <585C0758-B87C-11D7-8CCE-000393A3327C@fla.fujitsu.com>

+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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>>
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>
Received on Thursday, 17 July 2003 13:31:22 GMT

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