Applied in the Web services-based system, policy is used to convey conditions on an interaction between entities (requester application, provider service, Web infrastructure component, etc)Daniel RothDaniel Roth212006-09-13T18:42:00Z2006-09-13T18:42:00Z13401938Microsoft Corporation164227411.8026Applied in the Web services model-based system, policy is used to convey conditions on an interaction between a Web entities (requester application, provider service requestor and a Web service provider., Web infrastructure component, etc). Any entity in a Web services-based system may expose a policy to convey conditions under which it functions. Satisfying assertions in the policy usually results in behavior that reflects these conditions. Typically, the For example, if two entities – requester and provider – expose their policies, a requester might use the policy of a Web service exposes a policy to convey conditions under which it provides the service. A requester might use this policy provider to decide whether or not to use the service. A requester may choose any alternative since each is a valid configuration for interaction with the service, but a requester MUST choose only a single alternative for an interaction with a service since each represents an alternative configuration.A policy assertion is supported by a requesteran entity in the web services-based system if and only if the requesterentity satisfies the requirement (or accommodates the capability) corresponding to the assertion. A policy alternative is supported by a requesteran entity if and only if the requesterentity supports all the assertions in the alternative. And, a policy is supported by a requesteran entity if and only if the requesterentity supports at least one of the alternatives in the policy. Note that although policy alternatives are meant to be mutually exclusive, it cannot be decided in general whether or not more than one alternative can be supported at the same time.Note that a requesteran entity may be able to support a policy even if the requesterentity does not understand the type of each assertion in the vocabulary of the policy; the requesterentity only has to understand the type of each assertion in the vocabulary of a policy alternative the requesterentity supports. This characteristic is crucial to versioning and incremental deployment of new assertions because this allows a provider's policy to include new assertions in new alternatives while allowing requestersentities to continue to use old alternatives in a backward-compatible manner.