Service Oriented Model

Important Definitions

An action, for the purposes of this architecture, is any action that may be performed by an agent as a result of receiving a message, or results in sending a message or other observable state change.
A choreography defines the sequence and conditions under which multiple cooperating independent Web services exchange information in order to achieve some useful function.
A service is a set of actions that form a coherent whole from the point of view of service providers and service requesters.
The semantics of a service is the contract between the service provider and the service requester that expresses the effect of invoking the service. A service semantics may be formally described in a machine readable form, identified but not formally defined or informally defined via an `out of band' agreement between the provider and the requester.
A service task is a unit of activity associated with a service. It is denoted by a pair: a goal and an action; the goal denotes the intended effect of the task and the action denotes the process by which the goal is achieved.