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RE: Intermediaries

From: Ugo Corda <UCorda@SeeBeyond.com>
Date: Fri, 5 Dec 2003 10:51:54 -0800
Message-ID: <EDDE2977F3D216428E903370E3EBDDC9032B89C9@MAIL01.stc.com>
To: "Cutler, Roger (RogerCutler)" <RogerCutler@chevrontexaco.com>, <www-ws-arch@w3.org>

Right, because a gateway changes the message. So I understood your statement as saying that whenever the message is changed (including the gateway case) you have a choreography/orchestration node.

But rereading your note it now seems to me that you meant something else than what I originally understood (choreography=intermediary), i.e. the idea of choreography as a way of describing the passage of messages through a set of nodes in sequence. In that respect, you could use that concept regardless the fact that those nodes are intermediaries or not.

Ugo

> -----Original Message-----
> From: Cutler, Roger (RogerCutler) 
> [mailto:RogerCutler@chevrontexaco.com]
> Sent: Friday, December 05, 2003 10:41 AM
> To: Ugo Corda; www-ws-arch@w3.org
> Subject: RE: Intermediaries
> 
> 
> I believe that the sense I heard in the telcon was that a gateway was
> NOT an intermediary, but please feel free to change or use the text in
> any way you like.  I just submitted it as a straw man, based on my
> recollection of what seemed to be the consensus of the conversation.
> 
> -----Original Message-----
> From: www-ws-arch-request@w3.org 
> [mailto:www-ws-arch-request@w3.org] On
> Behalf Of Ugo Corda
> Sent: Friday, December 05, 2003 11:22 AM
> To: Cutler, Roger (RogerCutler); www-ws-arch@w3.org
> Subject: RE: Intermediaries
> 
> 
> 
> 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 13:51:55 GMT

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