Simulation, verification and automated composition of web services

Abstract

Web services --Web-accessible programs and devices -are a key application area for the Semantic Web. With the proliferation of Web services and the evolution towards the Semantic Web comes the opportunity to automate various Web services tasks. Our objective is to enable markup and automated reasoning technology to describe, simulate, compose, test, and verify compositions of Web services. We take as our starting point the DAML-S DAML+OIL ontology for describing the capabilities of Web services. We define the semantics for a relevant subset of DAML-S in terms of a first-order logical language. With the semantics in hand, we encode our service descriptions in a Petri Net formalism and provide decision procedures for Web service simulation, verification and composition. We also provide an analysis of the complexity of these tasks under different restrictions to the DAML-S composite services we can describe. Finally, we present an implementation of our analysis techniques. This implementation takes as input a DAML-S description of a Web service, automatically generates a Petri Net and performs the desired analysis. Such a tool has broad applicability both as a back end to existing manual Web service composition tools, and as a stand-alone tool for Web service developers.

DAML-S: Web Service Description for the Semantic Web

“…locating Web Services (typically through a registry service) that provide a particular service and that adhere to specified constraints; invocation or activation and execution of an identified service by an agent or other service; interoperation, i.e. breaking down interoperability barriers through semantics, and the automatic insertion of message parameter translations between clients and services [10,13,22]; composition of new services through automatic selection, composition and interoperation of existing services [15,14]; verification of service properties [19]; and execution monitoring, i.e. tracking the execution of complex or composite tasks performed by a service or a set of services, thus identifying failure cases, or providing explanations of different execution traces.…”

“…Recently, we have developed proposals for both an model-theoretic and an execution semantics for DAML-S descriptions. [19,1]. One approach provides a model-theoretic semantics by describing the intended interpretation of DAML-S in a more expressive first-order logic language [19].…”

Process-Level Composition of Executable Web Services: ”On-the-fly” Versus ”Once-for-all” Composition

“…However, none of these techniques addresses the problem of composing web services with conditional outputs, non-nominal outcomes, and with process models describing interaction protocols that include conditional and iterative steps. In [8,11,7], the authors propose an approach to the automated composition of web services based on a translation of DAML-S to situation calculus and Petri Nets. Also in these papers, however, the automated composition is limited to sequential composition of atomic services, and composition requirements are limited to reachability conditions.…”

A Compositional Operational Semantics for OWL-S

“…The original semantics for DAML-S were provided via translation to Petri Nets [7]. As well as problems with providing compositionality for a mathematical semantics for these, the translation was fundamentally non-compositional.…”