Microsoft, IBM Top Off Web Services Metadata Spec

Microsoft, IBM, BEA Systems and SAP have wrapped up their specification for defining messages to retrieve specific types of metadata associated with a recipient.

The spec, Web Services Metadata Exchange for Service Endpoints (WS-MetadataExchange), is the latest stone along the vendors’ roadmap to define unity and clarity of purpose for Web services, which allow applications to talk to one another.

Microsoft , IBM and other software makers have been working steadily to develop Web services specs because a paucity of standards concerning management, interoperability and security has held back Web services to this point.

Microsoft and IBM have been sticking to their roadmap to create specs they send to OASIS or the World Wide Web Consortium for review and possible passage as standards. Other standards on this map include WS-ReliableMessaging, WS-Addressing and WS-Transactions and WS-Coordination.

According to a document recently published by the four vendors, the WS-MetadataExchange spec defines a “bootstrap mechanism” for exchanging messages based on metadata, or data about data. In an e-mail file, metadata is the information that describes the comings and goings of the e-mail, the size of the e-mail, and other defining features.

WS-Metadata is a piece of the data puzzle for Web services because it provides information such as the XML Schema, the Web Services Policy Framework (WS-Policy) and Web Services Description Language (WSDL) 1.1.

For example, WS-Metadata could tell a user whom the information is from, whom it is going to, as well as details about the content and what the Web services are allows or required to do.

While WS-Policy is used to describe the capabilities and requirements of Web services, WSDL 1.1 describes message operations, and XML Schema describes the structure and content of XML messages. WS-MetadataExchange bootstraps, or ties, the three together in the following way:

“To bootstrap communication with a Web service, this WS-MetadataExchange specification defines three request-response message pairs to retrieve these three types of metadata,” according to a document on the Web. “One retrieves the WS-Policy associated with the receiving endpoint or with a given target namespace, another retrieves either the WSDL associated with the receiving endpoint or with a given target namespace, and a third retrieves the XML Schema with a given target namespace. Together these messages allow efficient, incremental retrieval of a Web service’s metadata.”

The specification is an initial public draft release and is up for review for later submission to a standards body, likely OASIS.