Researchers at HP Laboratories have developed extensions to the Web Services Conversation Language (WSCL) that support 'transformational interactions' for message coordination between web/peer services. Hewlett-Packard's WSCL specification of May 2001 "allows defining the abstract interfaces of web services, i.e., the business level conversations or public processes supported by a web service; WSCL specifies the XML documents being exchanged, and the allowed sequencing of these document exchanges. WSCL adopts an approach from the domain of software agents, modelling protocols for business interaction as conversation policies, but extends this approach to exploit the fact that service messages are XML-based business documents and can thus be mapped to XML document types." The HP research team has now designed a facilitator service mechanism "that can leverage 'reflected' XML-based specifications (borrowed from the web service domain) to direct and enable coordinated sequences of message exchanges (conversation) between services. They extend the usage of WSCL to include mappings of the input and output document types to corresponding document transformations, and call these extended message exchanges 'transformational interactions.' The facilitator service can use these transformational interactions to allow service developers to decouple internal and external interfaces. This means that services can be developed and treated as pools of methods that can be composed dynamically."
Web Services Conversation Language (WSCL) provides an XML schema for defining legal sequences of documents that web-services can exchange. WSCL "allows defining the abstract interfaces of web services, i.e., the business level conversations or public processes supported by a web service. WSCL specifies the XML documents being exchanged, and the allowed sequencing of these document exchanges. WSCL conversation definitions are themselves XML documents, and can therefore be interpreted by web services infrastructures and development tools. WSCL may be used in conjunction with other service description languages like WSDL, e.g., to provide protocol binding information for abstract interfaces and to specify the abstract interfaces a concrete service is supporting." [From the WSCL specification abstract]
WSCL version 1.0 is derived from the Conversation Definition Language (CDL) as defined in the HP Service Framework Specification (SFS). The service framework specification "is a layered specification that enables interoperability through the use of XML and formal definitions of interactions amongst services. It also provides mechanisms for dynamically discovering services as well as interacting with them through the exchange of XML documents. The specification has two parts: the first part specifies more horizontal infrastructural services such a messaging, service definition, transactions, management, vocabularies, and discovery of services. The second part focuses on higher level business interactions such as negotiation and contract formation."
- Web Services Conversation Language (WSCL) 1.0. By Arindam Banerji, Claudio Bartolini, Dorothea Beringer, Venkatesh Chopella, Kannan Govindarajan, Alan Karp, Harumi Kuno, Mike Lemon, Gregory Pogossiants, Shamik Sharma, and Scott Williams. May 2001. Hewlett-Packard Company. 21 pages. [cache]
- WSCL XML Schema Definition and Example WSCL Specification. From the May 2001 specification (Appendices A and B).
- "Transformational Interactions for P2P E-Commerce." By Harumi Kuno, Mike Lemon, and Alan Karp (Software Technology Laboratory, HP Laboratories Palo Alto, California). HP Reference: HPL-2001-143 (R.1). October 10, 2001.
- "Web Services Conversation Language (WSCL)" - Main reference page.