Behavioral Description of Services

Functional descriptions facilitate the process of discovering Semantic Web services. As we have seen in the previous chapter, they provide a high level characterization of the underlying service by defining conditions on the input and output, as well as the state of the world before and after Web service execution. These conditions correspond to a (single) transition from the prestate– the state before execution – to the post-state– the state after execution.

Although this is already a significant step towards automated discovery, composition and execution of Web services, more detailed descriptions are needed for the automated usage (invocation) of Web services. In fact, the typical interaction with aWeb service comprises a number of steps, where each step corresponds to sending or receiving a message. Now, there are different possible interactions between a requester and a Web service. A description of all possible interactions is called the behavioral modelof the Web service. It includes such things as the ordering of inputs and outputs and conditions governing the exchange of messages.

Behavioral models are of special significance in the context of Business Process Integration, which is the controlled sharing of data and business processes among connected applications and data sources within an enterprise and between trading partners [105]. Business Process Integration occurs in a number of different contexts. For example, (1) exchanging business documents, (2) integrating applications in an enterprise, and (3) establishing relations with new business partners. Behavioral models play an important role in all of these contexts, but most significantly in the latter. By checking the compatibilityof the behavioral models of two Web services one can determine whether they can potentially interact [100, 23, 101].