Abstract: In this paper we present Colombo, a framework in which web services are characterized in terms of (i) the atomic processes (i.e., operations) they can perform; (ii) their impact on the “real world ” (modeled as a relational database); (iii) their transition-based behavior; and (iv) the messages they can send and receive (from/to other web services and “human ” clients). As such, Colombo combines key elements from the standards and research literature on (semantic) web services. Using Colombo, we study the problem of automatic service composition (synthesis) and devise a sound, complete and terminating algorithm for building a composite service. Specifically, the paper develops (i) a technique for handling the data, which ranges over an infinite domain, in a finite, symbolic way, and (ii) a technique to automatically synthesize composite web services, based on Propositional Dynamic Logic. 1

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We present an OWL-S service composition planner, called OWLS-Xplan, that allows for fast and flexible composition of OWL-S services in the semantic Web. OWLS-Xplan converts OWL-S 1.1 services to equivalent problem and domain descriptions that are specified in the planning domain description language PDDL 2.1, and invokes an efficient AI planner Xplan to generate a service composition plan sequence that satisfies a given goal. Xplan extends an action based FastForward-planner with a HTN planning and re-planning component.

Abstract. In many Web service composition problems, information may be needed from Web services during the composition process. Existing research on Web service composition (WSC) procedures has generally assumed that this information will not change. We describe two ways to take such WSC procedures and systematically modify them to deal with volatile information. The black-box approach requires no knowledge of the WSC procedure’s internals: it places a wrapper around the WSC procedure to deal with volatile information. The gray-box approach requires partial information of those internals, in order to insert coding to perform certain bookkeeping operations. We show theoretically that both approaches work correctly. We present experimental results showing that the WSC procedures produced by the gray-box approach can run much faster than the ones produced by the black-box approach. 1

Workflow templates are necessary for various different Web Service related tasks such as encoding business rules in a B2B application, specifying domain knowledge in a scientific Grid application, and defining preferences for users that interact with Web Services. Abstract activities in templates can be used to specify the features of a required service and concretes service can be discovered and used to generate executable workflows. In this paper, we examine how Web ontologies can be used to write such template descriptions that will allow flexible matchmaking of services. We discuss the importance of expressing preferences in templates and provide a ranking algorithm based on DL inference services. We then present the HTN-DL formalism – an extension to the HTN planning formalism to generate compositions of Web Services based on these templates. Finally we present the experimental evaluation for the composition system we proposed.

Web service composition has quickly become a key area of research in the services oriented architecture community. One of the challenges in composition is the existence of heterogeneities across independently created and autonomously managed Web service requesters and Web service providers. Previous work in this area either involved significant human effort or in cases of the efforts seeking to provide largely automated approaches, overlooked the problem of data heterogeneities, resulting in partial solutions that would not support executable workflow for real-world problems. In this paper, we present a planning-based approach to solve both the process heterogeneity and data heterogeneity problems. Our system successfully outputs an executable BPEL file which correctly solves non-trivial real-world process specifications outlind in the 2006 SWS Challenge. 1.

Abstract. Semantic annotations of web services can facilitate the discovery of services, as well as their composition into workflows. At present, however, the practical utility of such annotations is limited by the small number of service annotations available for general use. Resources for manual annotation are scarce, and therefore some means is required by which services can be automatically (or semi-automatically) annotated. In this paper, we show how information can be inferred about the semantics of operation parameters based on their connections to other (annotated) operation parameters within tried-and-tested workflows. In an open-world context, we can infer only constraints on the semantics of parameters, but these loose annotations are still of value in detecting errors within workflows, annotations and ontologies, as well as in simplifying the manual annotation task. 1

Abstract. Automated service composition is an important approach to automatically aggregate existing functionality. While different planning algorithms are applied in this area, heuristic search is currently not used. Lacking features like the creation of compositions with parallel or alternative control flow are preventing its application. The prospect of using heuristic search for composition with quality of service properties motivated the extension of existing heuristic search algorithms. In this paper we present a heuristic search algorithm for automated service composition. Based on the requirements for automated service composition, shortcomings of existing algorithms are identified, and solutions for them presented.

Automated matching of semantic service descriptions is the key to automatic service discovery and binding. But when trying to find a match for a certain request it may often happen, that the request cannot be serviced by a single offer but could be handled by combining existing offers. In this case automatic service composition is needed. Although automatic composition is an active field of research it is mainly viewed as a planning problem and treated separatedly from service discovery. In this paper we argue that an integrated approach to the problem is better than seperating these issues as is usually done. We propose an approach that integrates service composition into service discovery and matchmaking to match service requests that ask for multiple connected effects, discuss general issues involved in describing and matching such services and present an efficient algorithm implementing our ideas.

Abstract. In Web Service Composition (WSC) problems, the composition process generates a composition (i.e., a plan) of atomic services, whose execution achieves some objectives on the Web. Existing research on Web service composition generally assumed that these objectives are absolute; i.e., the servicecomposition algorithms must achieve all of them in order to generate successful outcomes; otherwise, the composition process fails altogether. The most straightforward example is the use of OWL-S process models that specifically tell a composition algorithm how to achieve a functionality on the Web. However, in many WSC problems, it is also desirable to achieve users ’ preferences that are not absolute objectives; instead, a solution composition generated by a WSC algorithm must satisfy those preferences as much as possible. In this paper, we first describe a way to augment OWL-S process models by qualitative user preferences. We achieve this by mapping a given set of process models and preferences into a planning language for representing Hierarchical Task Networks (HTNs). We then present SCUP, our new WSC algorithm that performs a best-first search over the possible HTN-style task decompositions, by heuristically scoring those decompositions based on ontological reasoning over the input preferences. Finally, we discuss our experimental results on the SCUP algorithm. 1