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RE: Intermediaries

From: Ugo Corda <UCorda@SeeBeyond.com>
Date: Fri, 5 Dec 2003 09:21:51 -0800
Message-ID: <EDDE2977F3D216428E903370E3EBDDC9032B89C5@MAIL01.stc.com>
To: "Cutler, Roger (RogerCutler)" <RogerCutler@chevrontexaco.com>, <www-ws-arch@w3.org>

Roger,

I would not use the term choreography. According to my current understanding of WS-Chor, a choreography is a way of describing the patterns of message exchanges among a set of participant nodes, and of describing the change of state of those nodes. A choreography does not map to an node/agent, so I would leave it out of the intermediary discussions.

Orchestration is a more appropriate term for this discussion. Still I would not say that in general "if the purpose or function of the message is substantially changed one should consider the situation to be an orchestration". For instance, I don't think many people would think of a simple gateway as an orchestration node.

Ugo

> -----Original Message-----
> From: www-ws-arch-request@w3.org [mailto:www-ws-arch-request@w3.org]On
> Behalf Of Cutler, Roger (RogerCutler)
> Sent: Friday, December 05, 2003 7:44 AM
> To: www-ws-arch@w3.org
> Subject: Intermediaries
> 
> 
> 
> Here is some text that expresses my understanding of the sense of some
> of the telcon conversation about intermediaries.  Please use, 
> modify or
> ignor as seems appropriate.
> 
> It is useful to draw a distinction between situations where 
> messages are
> passed through intermediaries and choreographies.  The essential issue
> is that an intermediary passes along a message that is essentially, or
> functionally, the same as it received.  If, on the other hand, the
> purpose or function of the message is substantially changed one should
> consider the situation to be a choreography.  This cannot be defined,
> however, in an entirely rigorous or black and white way -- 
> one person's
> intermediary may legitimately be considered a choreography by others.
> Note that since an intermediary can change the message, for example by
> encrypting it or by adding ancillary information, it remains 
> a judgment
> call whether those changes are significant and functional.  
> In addition,
> whether a service that passes messages is considered an intermediary
> depends on participants in the entire chain of the message.  For
> example, if sender A sends messages through I, which modifies the
> messages, to receivers B and C, B might consider the modified 
> message to
> be functionally unchanged whereas C might consider it to be different
> and take different action because of the modification.  In the first
> case I would be considered an intermediary, in the second it 
> would not. 
> 
> 
Received on Friday, 5 December 2003 12:21:52 GMT

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