Many higher level
software systems have already chosen the standard Web services as building blocks.
Some examples are grid services and the Semantic Web-enabled Web services.
In the Web services discovery system, the Web services architecture has three major
roles: (1) a service provider, (2) a service consumer, and (3) a directory. Such an
architecture enables a loose coupling of service consumer and service provider: first,
the service provider publishes descriptions of its services to the directory. After that,
Web Serv ces D scovery and QoS-Aware Extens on
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the service consumer searches the directory to find information about an appropriate
provider and its service. Finally the service consumer binds to the chosen provider
and uses its service. This loose coupling is performed dynamically, that is, during
the run time. This publish-discovery-bind model of service interaction increases
the flexibility and agility of the Web services.
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