9.3. Summary
Explicit service description information (metadata) is a central aspect of SOAs and the Web services framework. Explicit metadata is the key to effective decoupling between service applications. Several mechanisms allow communicating metadata between service providers and requesters. Centralized registries such as UDDI rely on a third party to aggregate information about services and enable both discovery of services and retrieval of service descriptions. WS-MetadataExchange defines a WSDL interface so that service requesters can retrieve metadata directly from the service provider. This model does not support service discovery, but it's advantageous because a third-party infrastructure is not required for requesters to retrieve full information about a service provider. WS-MetadataExchange enables dynamic configuration at the requester side and allows providers to dynamically customize their policies based on the identity of the requester or specific conditions under which the interaction takes place. For this reason, WS-Metadata is a key piece for bootstrapping service interactions. Finally, the WS-MetadataExchange interface can accommodate additional metadata types beyond the ones commonly considered today (XML Schema, WSDL, and WS-Policy), such as semantic service descriptions. |
لطفا منتظر باشید ...
