The Service Metadata is an expression of visible aspects of Web service behavior. Service Metadata is represented by a mixture of machine- and human-readable languages. Machine readable languages enable tooling. Service Metadata is a subset of the spectrum of general metadata. There are many popular points in this Service Metadata subset.
First popular point in the Service Metadata is the message interchange format within the SOAP Message Construct. That is, representing SOAP Body Children and SOAP Header Blocks. Industry uses XML Schema language for representing message interchange format.
Second popular point in the Service Metadata is ‘how’ and ‘where’ messages are exchanged. That is, representing the concrete message format, what headers are used, transmission protocol, message exchange pattern, and endpoint. Industry uses WSDL for representing ‘how’ and ‘where’ messages are exchanged. WSDL has extensible points that can be used to expand on ‘how’ and ‘where’ representations.
Third popular point in the Service Metadata is the representation of capabilities and requirements for interacting with Web service endpoints. That is, representing whether and how a message must be secured, whether and how a message must be delivered reliably, etc.
WS-Policy is a new machine-readable language for representing Web service capabilities and requirements as Policies.
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