1. In a Web services environment for exchanging messages in a distributed system, a method of identifying policies mapped to messages associated with an application, without having to have code within the application for determining what policies may apply to the messages, the method comprising the acts of: receiving a message at a Web service engine associated with an application that is external to the Web service engine, the application configured to exchange messages in a distributed system; based on the contents of the received message, determining at least a destination endpoint identifier associated with the message; accessing a policy mapping file that includes one or more endpoint sections, each of the one or more endpoint sections including one or more operation elements that indicate a type of interaction pattern for messages, wherein at least one of the one or more operation elements identifies one or more policy expression with one or more policy assertions representing policies associated with exchanging messages with the application; and scanning the policy mapping file for identifying an operation element corresponding to the destination endpoint identifier.