Use of Colored Petri Nets to Model, Analyze, and Evaluate Service Composition and Orchestration

The Concurrency, communications, resource constraints, and quality of service attributes are distinguishing features of web services. Assessment and determination of impact of the nonfunctional aspects such as service granularity, governance, composition, and orchestration is an overarching concern and this exercise should be carried out at the architecture design stage rather than post implementation and deployment. In this paper we illustrate, by means of a simple example, the use of Colored Petri Nets (CPNs) to model service composition and orchestration. We use the associated software tool called CPN Tools to perform the analysis. The results can be used in many ways such as to determine design alternative or to check conformance with existing service level agreements, etc. Colored Petri Nets, being a graphical modeling language suitable for modeling distributed, concurrent, deterministic and nondeterministic systems with synchronous and asynchronous communications, offer a natural choice for this endeavor. Although the example is given in the context of web services, CPNs view of interaction and coordination of systems is abstract and can be applied to different notions of services equally well.