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Team Comment on the WSCL Submission

W3C is pleased to receive the WSCL Submission from Hewlett-Packard Company.

A single communication between two parties in the context of Web services is usually part of a larger application-level process, i.e. a complex set of interactions. The Web Services Conversation Language (WSCL) 1.0 allows the description of sequences interactions with a Web service, called conversations.

The format of the XML documents exchanged are called document type descriptions and are expressed as references to XML schemas. The exchanges of inbound and outbound documents with a Web service are called interactions.

An application-level communication is likely to be composed of a sequence of interactions and can be modeled as a UML activity diagram. WSCL allows description of the transitions from one interaction (activity) to another, which can be based on the result of an interaction.

WSCL doesn't address the protocol binding aspect of the interactions nor the instantiation of the abstract interfaces described. The specification includes a section about how to combine WSCL with WSDL, which addresses those aspects.

WSCL 1.0 relates to the following W3C Activities and events:

Web Services Activity
Conversation is one aspect of Web services interactions. The Web Services Architecture Working Group is chartered to design a framework for Web services to reach their full potential.
The Web Services Description Working Group is working on defining a description language for Web services based on WSDL 1.1.
Parties exchange XML messages. The XML Protocol Working Group is developing an XML-based protocol, SOAP Version 1.2, which can be used as a messaging framework for communication between both parties.
XML Schema
The format of the payload of the messages exchanged is described as XML schemas.
Semantic Web
The Semantic Web aims at designing a machine-processable Web. WSCL's goals fit into this scope.

Section 2.6 introduces the concept of well-formed conversation definitions, which are XML documents validating the WSCL 1.0 schema, describing conversations which have certain constraints on their interactions and transitions. Well-formed documents being a meaningful term for XML documents, it would be better to call those conversations another way, such as semantically meaningful. The constraints described for such conversations echo the work done at W3C in the Web Ontology Working Group, and may be described in a computer-readable way.

WSCL aims at being a simple definition language, and therefore has limitations. Section 5 of the specification gives examples about how the language could be extended.

Next Steps

The WSCL submission will be brought to the attention of the Web Services Architecture Working Group and of the Web Services Description Working Group.

The submission will also be brought to the attention of the Web Ontology Working Group as a potential use case for the Web Ontology language designed.

Feedback on this technology is encouraged on the www-ws mailing list (public archive).

Disclaimer: Placing a Submission on a Working Group/Interest Group agenda does not imply endorsement by either the W3C Team or the participants of the Working Group/Interest Group, nor does it guarantee that the Working Group/Interest Group will agree to take any specific action on a Submission.

Hugo Haas, Team contact for the Web Services Architecture Working Group <hugo@w3.org>