Attaching Policies to Service Objects for Clients

Clients access services through an object - e.g. an instance of a class like SearchEngine
Service hosts create these objects and attach a particular policy to each one.
As clients use the service object, by invoking methods, the policy determines whether each call will proceed or not, based on the current state of the policy's FSM.
By default client code blocks - but a language extension allows clients to hedge their bets.

Clients access services through an object - e.g. an instance of a class like SearchEngine