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RE: BPSS_f2f_june03.ppt

From: Ugo Corda <UCorda@SeeBeyond.com>
Date: Fri, 20 Jun 2003 10:15:24 -0700
Message-ID: <EDDE2977F3D216428E903370E3EBDDC9081204@MAIL01.stc.com>
To: "Jean-Jacques Dubray" <jjd@eigner.com>, <public-ws-chor@w3.org>

JJ,

Let me see if I understand your concept of choreography protocol by asking some concrete questions. 

I imagine you are proposing to define such a protocol at the abstract level (i.e. part of the choreography abstract language we have been talking about). So at the time we need to develop an executable process we would have to map that abstract protocol to the specific executable language/protocols we plan to use.

In the case of executable BPEL, would the abstract choreography protocol map to specific BPEL messages (i.e. your choreography protocol would have corresponding parts in the  WSDL descriptions of related messages)? Or would it map to other BPEL features other than message contents?

If it maps to message contents and the WSDL interfaces happen to be bound to SOAP, would that choreography protocol be mapped to a SOAP module (i.e. SOAP headers)? Do you envision a new spec that defines a SOAP-based choreography protocol?

Thank you,
Ugo

> -----Original Message-----
> From: Jean-Jacques Dubray [mailto:jjd@eigner.com]
> Sent: Friday, June 20, 2003 4:30 AM
> To: Ugo Corda; 'Jean-Jacques Dubray'; public-ws-chor@w3.org
> Subject: RE: BPSS_f2f_june03.ppt
> 
> 
> Ugo:
> 
> Basically a choreography protocol is needed to ensure that 
> each peer in
> the choreography has the same view of the state in which the
> choreography instance is. Imagine a situation, where you send me a PO
> and I am not supposed to respond until the goods are shipped 
> and I will
> respond by sending you an invoice. So you send me a PO and 
> the RM tells
> you "I got it" (just like a fax). The next thing that should 
> happen then
> is you receive the goods and later on an invoice. If there was a human
> behind a fax machine, and the order was garbled he could call 
> and figure
> out the right information. In this case, the sender things the
> choreography is going ok. The responder on the contrary 
> thinks that the
> collaboration is terminated on an error. This is why you need a
> protocol: to tell you that no exception occurred, each party has the
> same view of the state of the choreography.
> 
> If you take a "highly-connected" system that has several hundred /
> thousands participants (not all participating in the same choreography
> instance but rather having 2 by 2 conversations). You cannot 
> expect that
> every message that will be exchanged in this setting would be of high
> quality (the structure may be old or wrong, the content may be
> incoherent making the processing of the message impossible, i.e. a
> response cannot be created because the message could not get into the
> system that was supposed to create the response). 
> 
> At this point, you can say I don't need/want a protocol. That 
> means that
> when a choreography is designed, the designers must account for these
> possible (yet common) errors. They will create specific 
> messages to say
> "could not process your orders, it contains errors", and make these
> messages part of the choreography.
> 
> On the other hand if you had a protocol, you would have a standard set
> of exceptions (common to all message exchanges) and 
> materialized with a
> set of standard messages. You could then express the 
> choreography paths
> based on these error conditions (if success ... if failure ... if
> timeout ... if structure invalid ... if content invalid ...) with an
> implicit message exchange. The simplest set of exception for me are:
> message did not get there on time, message could not be processed by
> system/service of record.
> 
> Again, all this has nothing to do with RM. The problem here 
> is not that
> your message did not get to the recipient, it is rather that the
> recipient got a message that he could not process, hence interrupting
> the choreography instance. A protocol would help you cover 
> 80/90% of the
> common exceptions. Others can be dealt with at the design level.
> 
> Cheers,
> 
> Jean-Jacques Dubray____________________
> Chief Architect
> Eigner  Precision Lifecycle Management
> 200 Fifth Avenue
> Waltham, MA 02451
> 781-472-6317
> jjd@eigner.com
> www.eigner.com 
>  
>  
> 
> >>-----Original Message-----
> >>From: Ugo Corda [mailto:UCorda@SeeBeyond.com]
> >>Sent: Donnerstag, 19. Juni 2003 22:14
> >>To: Jean-Jacques Dubray; public-ws-chor@w3.org
> >>Subject: RE: BPSS_f2f_june03.ppt
> >>
> >>Jean-Jacques,
> >>
> >>I did not have a chance to listen to your presentation, so you might
> have
> >>already explained this. In your slides you talk about a 
> "choreography
> >>protocol", and I am not sure whether it is just regular 
> messages plus
> an
> >>instance ID (as you mentioned in a previous message to the 
> list) or it
> is
> >>more than that.
> >>
> >>Thank you,
> >>Ugo
> >>
> >>> -----Original Message-----
> >>> From: Martin Chapman [mailto:martin.chapman@oracle.com]
> >>> Sent: Thursday, June 19, 2003 12:18 PM
> >>> To: public-ws-chor@w3.org
> >>> Subject: FW: BPSS_f2f_june03.ppt
> >>>
> >>>
> >>>
> >>>
> >>> -----Original Message-----
> >>> From: Jean-Jacques Dubray [mailto:jjd@eigner.com]
> >>> Sent: Thursday, June 19, 2003 10:23 AM
> >>> To: 'Martin Chapman'; 'Steve Ross-Talbot';
> Daniel_Austin@grainger.com
> >>> Subject: BPSS_f2f_june03.ppt
> >>>
> >>>
> >>> Martin et al:
> >>>
> >>> This is my presentation for this afternoon. Please let me
> >>> know what time
> >>> and which number to call.
> >>>
> >>> Best regards,
> >>>
> >>> JJ-
> >>> 781-472-6317
> >>>
> 
> 
Received on Friday, 20 June 2003 13:15:33 GMT

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