Approaching Web Service Coordination and Composition by Means of Petri Nets. The Case of the Nets-within-Nets Paradigm

摘要

Web service coordination and composition have become a central topic for the development of Internet-based distributed computing. A wide variety of different standards have been defined to deal with the composition of Web services (usually represented as workflows) and the execution of coordination protocols. On the other hand, some relevant research proposals have already pointed to the use of the same formalism for both aspects, being Petri nets one of the adopted formalisms. In this work we present a case study showing how the adoption of the Nets-within-Nets paradigm helps in the modelling of complex coordination protocols and workflows. We first propose a Petri net model for a Web service peer able to run any workflow and to dynamically interpret the coordination required protocols. The execution of these protocols allows the peer to integrate functionalities offered by external peers. The Linda communication model has been used to support the integration among peers.