Policies define the business requirements that have to be met when a consumer requests a service.
A policy is a set of Assertions that represent requirements, constraints or capabilities for a Business Service. For example, "A Business Service must use HTTP or HTTPS as a medium of communication" is the example of a policy.
At runtime, the IBM® Business Services Dynamic Assembler determines the set of policies that are relevant for the request, and then locates the best endpoints that meet these requirements.
Policies are executed at runtime by the IBM® Business Services Dynamic Assembler, which dynamically selects the most appropriate endpoint based on the policies. The IBM Business Services Dynamic Assembler is a semantic mediation engine that is highly scalable and uses policy-based composition and semantic mediation for dynamic service assembly and service behavior adaptation based on content, context, and contract.
Policies can target application suites, applications, business services, interfaces and other types of resources. Each business service can be composed of multiple interfaces. Each Interface can be associated with multiple Endpoints. If we apply a policy on a business service then that policy applies to all associated interfaces and also to the endpoints associated with the interfaces.