Abstract not found

In this paper we study automatic composition synthesis of e-Services, based on automated reasoning. We represent the behavior of an e-Service in terms of a deterministic transition system (or a finite state machine), in which for each action the role of the e-Service, either as initiator or as servant, is highlighted. In this setting we present an algorithm based on satisfiability in a variant of Propositional Dynamic Logic that solves the automatic composition problem. Specifically, given (i) a possibly incomplete specification of the sequences of actions that a client would like to realize, and (ii) aset of available e-Services, our technique synthesizes a composite e-Service that (i) uses only the available e-Services and (ii) interacts with the client “in accordance” to the given specification. We also study the computational complexity of the proposed algorithm.

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

Abstract. In [3] we started studying an advanced form of service composition where available services were modeled as deterministic finite transition systems, describing the possible conversations they can have with clients, and where the client request was itself expressed as a (virtual) service making use of the same alphabet of actions. In [4] we extended our studies by considering the case in which the client request was loosen by allowing don’t care nondeterminism in expressing the required target service. In the present paper we complete such a line of investigation, by considering the case in which the available services are only partially controllable and must be modeled as nondeterministic finite transition systems, possibly because of our lack of information on their exact behavior. Notably such services display a “devilish ” form of nondeterminism, since we want to model the inability of the orchestrator to actually choose between different executions of the same action. We investigate how to automatically perform the synthesis of the composition under these circumstances. 1

agents and web services

ConGolog is a logical programming language for agents that is defined in the situation calculus. ConGolog agent control programs were originally proposed as an alternative to planning, but have also more recently been proposed as a means of providing domain control knowledge for planning. In this paper, we present a compiler that takes a ConGolog program and produces a new basic action theory of the situation calculus whose executable situations are all and only those that are permitted by the program. The size of the resulting theory is quadratic in the size of the original program – even in the face of unbounded loops, recursion, and concurrency. The compilation is of both theoretical and practical interest. From a theoretical perspective, proving properties of Con-Golog programs is simplified because reification of programs is no longer required, and the compiled theory contains fewer second-order axioms. Further, in some cases, properties can be proven by regressing the program to the initial situation, eliminating the need for a higher order theorem prover. From a practical perspective, the compilation provides the mathematical foundation for compiling ConGolog programs into classical planning problems, including, with minor restrictions, into the Plan Domain Definition Language (PDDL), which is used as the input language for most state-of-the-art planners. Moreover, Hierarchical Task Networks (HTNs), a popular planning paradigm for industrial applications can be represented as ConGolog programs and can thus now also be compiled to a classical planning problem. Such compilations are significant because they allow the best state-of-theart planners to exploit ConGolog and HTN search control, without the need for special-purpose machinery.

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

SHOP and SHOP2 are HTN planning systems that were designed with two goals in mind: to investigate some research issues in automated planning, and to provide some simple, practical planning tools. They are available as open-source software, and have developed an active base of users in government, industry, and universities. SHOP2 received one of the top four awards in the 2002 International Planning Competition [4]. This paper summarizes how SHOP and SHOP2 work, describes some of the applications that users have developed for them, and discusses directions for future work.

Abstract. The task of automatically composing Web services involves two main composition processes, vertical and horizontal composition. Vertical composition consists of defining an appropriate combination of simple processes to perform a composition task. Horizontal composition process consists of determining the most appropriate Web service, from among a set of functionally equivalent ones for each component process. Several recent research efforts have dealt with the Web service composition problem. Nevertheless, most of them tackled only the vertical composition of Web services despite the growing trend towards functionally equivalent Web services. In an attempt to facilitate and streamline the process of horizontal composition of Web services while taking the above limitation into consideration, this work includes two main contributions. The first is a generic formalization of any Web service composition problem based on a constraint optimization problem (COP); this formalization is compatible to any Web service description language. The second contribution is an incremental userintervention-based protocol to find the optimal composite Web service according to some predefined criteria at run-time. Our goal is i) to deal with many crucial natural features of Web services such as dynamic and distributed environment, uncertain and incomplete Web service information, etc; and ii) to allow human user intervention to enhance the solving process. Three approaches are described in this work, a centralized approach, a distributed approach and a multi-agent approach to deal with realistic domains. 1