- From: Champion, Mike <Mike.Champion@SoftwareAG-USA.com>
- Date: Thu, 26 Jun 2003 08:15:02 -0600
- To: www-ws-arch@w3.org
[Duh, yet another attempt ... sent it to the admin list by mistake!] [sorry, I mistyped the address in the first attempt, and Outlook perpetuated the typo in some of the headers after I re-sent. Please reply to this version or yours will bounce. Sigh. Also, look out for David Burdett's response, it's very useful!] --------------------------------------------------------------------------- Compare with http://www.w3.org/TR/2003/WD-ws-arch-20030514/#choreography Summary of changes: wordsmithed the draft text a bit to be more in line with recent discussions in the Choreography WG relating "choreography" to a shared global state machine rather than an execution language. Cross-checked language and issues here against the Choreography WG charter and various email-threads, notably: http://lists.w3.org/Archives/Public/www-ws-arch/2002Aug/0101.html http://lists.w3.org/Archives/Public/www-ws-arch/2002Aug/0191.html http://lists.w3.org/Archives/Public/www-ws-arch/2002Aug/0193.html http://lists.w3.org/Archives/Public/www-ws-arch/2002Oct/0205.html http://lists.w3.org/Archives/Public/www-ws-arch/2002Oct/0369.html http://lists.w3.org/Archives/Public/www-ws-arch/2003May/0033.html Issues: - Is the "shared state machine" definition too idiosyncratic and specific to the W3C WS-Chor WG? - Doe we want to wade into the swamp of defining "orchestration" or should we follow Martin's lead and simply ban the term :-) If so, does it mean "choreography implementation" or "sortof like choreography, but from a particular actor's point of view? See http://lists.w3.org/Archives/Public/www-ws-arch/2003May/0034.html - What's the relationship between Choreography and MEP? There was a sentiment at the WS-Chor F2F last week that a Choreography language should be able to model any MEP. -------------------------------------------------------------------------- XXX Choreography XXX.1 Definition A Choreography defines a shared state machine that describes interactions involving multiple web service invocations. XXX.2 Relationships to other elements A choreography is the pattern of possible interactions between a set of services A choreography may be expressed in a choreography description language XXX.3 Description SOAP and WSDL by themselves can describe only very simple Web services consisting of a single interaction between a consumer and provider pair. The SOAP Recommendation formally specifies only two MEPs, "Request-Response" and "SOAP Response." Web Services Choreography is the subject area describing web services interactions involving more than two parties and/or more than one operation. A choreography is model of th sequence of operations, states, and conditions which control how the interactions occur. Successfully following the pattern of interaction prescribed by a choreography should result in the completion of some useful function, for example: the placement of an order, information about its delivery and eventual payment, or putting the system into a well-defined error state. [ not sure about this: Defining the possible patterns of interactions between services does not itself construe a composite service; however, a composite service requires a definition in terms of the choreography of a set of services.] A choreography is not to be confused with orchestration. Orchestration is [option A: a technique for implementing a series of web service invocations described by a choreography, but is not the only such method.] [option B: defintion a series of web service invocations from a single single party's point of view (the conductor).] YYY Choreography Description Language YYY.1 Definition A Choreography Description Language is a notation for describing a choreography. It may also permit the specification of a composite service in terms of component services. YYY.2 Relationships to other elements A choreography Description Language describes the pattern of allowable interactions between a set of services A choreography Description Language may describe the life cycle of a service invocation A choreography Description Language describes the conversations possible between service requesters and service providers. YYY.3 Description A Choreography description language is a formal, machine-processable definition of a specific choreograpy. [Not sure about this: A choreography descripion language formally defines the message exchange pattern(s) used by a web service.] It permits the description of how Web services can be composed, how roles and associations in Web services can be established, and how the state, if any, of composed services is to be managed.
Received on Thursday, 26 June 2003 10:15:11 UTC