Automatic Composition of Semantic Web Services Based on Fuzzy Predicate Petri Nets

Web service composition is a challenging research issue. This paper presents an automatic Web service composition method that deals with both input/output compatibility and behavioral constraint compatibility of fuzzy semantic services. First, user input and output requirements are modeled as a set of facts and a goal statement in the Horn clauses, respectively. A service composition problem is transformed into a Horn clause logic reasoning problem. Next, a Fuzzy Predicate Petri Net (FPPN) is applied to model the Horn clause set, and T-invariant technique is used to determine the existence of composite services fulfilling the user input/output requirements. Then, two algorithms are presented to obtain the composite service satisfying behavioral constraints, as well as to construct an FPPN model that shows the calling order of the selected services. Note to Practitioners-Automatic Web service composition plays an increasingly important role in the rapid development of software applications to meet the fast-changing market needs. This work addresses the difficult and new issue of composing fuzzy semantic services based on user-supplied input and output requirements and behavioral constraints. Both Horn clause logic reasoning theory and fuzzy predicate Petri nets are used to develop polynomially complex algorithms for a desired composite service. A business service example is used to illustrate the proposed concepts and algorithms. The proposed methodology is readily applicable to industrial size Web service composition problems.