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

David,
 
My understanding of our characterization of web services is that they are services which support WSDL (including any WSDL bindings, i.e. protocols other than SOAP). 
WSDL takes care of both the abstract interface and the concrete bindings. 
So why would we need anything else besides web services and their requesters?
 
Ugo

-----Original Message-----
From: Burdett, David [mailto:david.burdett@commerceone.com]
Sent: Friday, July 18, 2003 1:45 PM
To: Ugo Corda; Burdett, David; Assaf Arkin; public-ws-chor@w3.org
Subject: RE: Grounding Choreographies (the atoms) - WAS Simple Choreograph y composition suggestion



Ugo 

I think that it is *necessary* to layer our choreography specs so that you have: 
1. A spec for an "abstract" choreography definition that describes the sequence and conditions in which messages are exchanged between roles, and

2. A spec for binding the abstract choreography definition to: physical message formats and physical service interface definitions.

The reason for this is that you can have the same abstract choreography, e.g. the buyer sending a PO and the seller sending a PO Response implemented in different ways such as:

1. Different formats for the message, e.g. SOAP 1.1 vs 1.2, vs SOAPWA, RosettaNet PO vs a UBL PO, etc, 
2. Different service interfaces, which use different service/actions in the WSDL to accept/generate SOAP messages 

If we don't have these two layers then it means that whenever standards evolve, e.g. SOAP 1.3 ;) or a new version of the RosettaNet PO, then the Choreography definition will also *have* to change even though its semantics have not.

However having this layering also means that you *could* do binding of the choreography defintion to other protocols, e.g ebXML Messaging. So what I am proposing though is that we do the abstract choreography spec and just the SOAP/Web Service binding without necessarily stopping other groups from doing alternative bindings if they want to.

Hope this answers your question. 

David 

-----Original Message----- 
From: Ugo Corda [ mailto:UCorda@SeeBeyond.com] 
Sent: Friday, July 18, 2003 1:09 PM 
To: Burdett, David; Assaf Arkin; public-ws-chor@w3.org 
Subject: RE: Grounding Choreographies (the atoms) - WAS Simple 
Choreograph y composition suggestion 


> If we say that Choreographies *always* have 
> to be *between* web services then it precludes the choreography being used 
> by something that is not a web service, which I don't think we want to do. 

My understanding of the previous discussion is that we want to include web service requesters as legitimate choreography participants. In this case the requester still talks to a web service according to the WSDL interface associated with that service.

Your statement seems to imply extending our choreography scope beyond web services and their requesters (e.g. to include services not described by WSDL). Could you please clarify?

Thank you, 
Ugo