Mediation

An intense research activity regarding the Semantic Web, Web Services, and their combination, Semantic Web Services, has been going on during the last few years. But only the semantic descriptions attached to data or to the Web Services deployed using today’s technologies do not solve the heterogeneity problem that may occur owing to the distributed nature of the Web itself. As such, the heterogeneity existing in representing data, in the multitude of choices in representing the requested and the provided functionalities, and in the differences in the communication patterns (public processes) are problems that have to be solved before we are able to fully benefit from the semantically enabled Web and Web Services. Considering that these problems cannot be avoided, dynamic mediation solutions that fully exploit the semantic descriptions of data and services are required.

This chapter is formed of two main parts: the first describes the main techniques for data mediation in a semantic environment, while the second focuses on behavior mismatches and process mediation.

The data mediation scenario to be analyzed in this chapter is the automatic transformation of the data part of heterogeneous messages exchanged in peer-to-peer (P2P) communications. One of the main assumptions in a semantic environment is that all manipulated data is described in terms of ontologies. As such, data to be mediated represents in fact ontology instances and the automatic mediation task relies on ontology mappings created during design time.

While data mediation solutions are mandatory in heterogeneous contexts, they are not enough to enable communication when mismatches at the behavioral level are also present. Solutions towards behavior mediation, where behavior is represented as processes, are discussed and a classification of solvable/unsolvable mismatches is provided.