Towards a First-Order Ontology for Semantic Web Services

We argue that an unambiguously, computer-interpretable description of the process model of a Web service, and a client’s constraints on that process model, are critical to automating a diversity of tasks, including Web service discovery, invocation, composition, monitoring, verification and simulation. That the process model descriptions be unambiguously computer-interpretable is key to our argument, and is a shortcoming of a number of existing process modeling frameworks that have been proposed to describe aspects of Web services. We commence this position paper with a brief overview of some existing process modeling frameworks used within the Web service community, providing analysis of some of their key merits and shortcomings. Next we present a small number of use cases that motivate and illustrate the need for computer-interpretable process models for the automation of Web service discovery and composition. With our use cases in hand, we propose a set of desiderata for a Web service description language that enables an unambiguous description of Web service process models. Our working hypothesis is that the process model be described as an ontology of first-order logic. To this end, we present the Process Specification Language (PSL) [5, 4], a first-order logic ontology for modeling processes, as a straw proposal for a foundation from which a Web service process modeling framework can be developed. The opinions expressed in this position paper reflect the position of the Semantic Web Services Language Committee (SWSL), a subcommittee of the joint North American-EU Semantic Web Services Intitiative (SWSI) (http://www.swsi.org). They are included in FLOWS, SWSL’s First-order Logic Ontology for Web Services [1].