Extending Web Service Composition Languages with Semantic Data Flow ∗ Freddy L´ ecu´ e 1 1 The University of Manchester Booth Street East, Manchester, UK {(firstname.lastname)@manchester.ac.uk} Alexandre Delteil 2 , Alain Leger 2 2 France Telecom R&D, France 4 rue du clos courtel, F-35512 Cesson S´ evign´ e {(firstname.lastname)@orange-ftgroup.com} Abstract Most of the work on automated Web service composi- tion has focused so far on composition of stateful Web ser- vices. This level of composition so called “Process Level” considers Web services with their internal and complex be- haviours. At process level formal models such as State Transition Systems (STS from now) or Interface Automata are the most appropriate models to represent the internal behaviour of stateful Web services. However such models focus only on semantics of their behaviours and unfortu- nately not on semantics of actions and their parameters. In this paper, we suggest to extending the STS model in the lat- ter direction w.r.t the semantic Web. This semantic enhance- ment of STS so called S 2 TS will enable to model semantics of internal behaviours and semantics of their actions to- gether with their input and output parameters. Secondly, we will focus on automated generation of data flow (or the pro- cess to perform automated assignments between services of a composition). Thus we do not restrict to assignments of exact parameters (which is practically never used in indus- trial scenario) but extend assignments to semantically close parameters (e.g., through a subsumption matching). Our system is implemented and interacting with Web services dedicated on Telecom scenarios. The preliminary evalua- tion results showed high efficiency and effectiveness of the proposed approach. 1 Introduction The semantic Web i.e., the Web of meaning is considered as the new vision and extension of the current Web that tries to give semantic to the Web resources. In such a new vision of the Web, Web services are semantically enhanced using rich description languages through Description Logics [3] such as the Web Ontology Language (OWL) [23]. Seman- tic Web services are then Web services that have been aug- ∗ Foundation Project: Supported by European Commission VII Frame- work IP Project Soa4All. mented with formal semantic descriptions where OWL-S [2], WSMO [6] or SA-WSDL [22] can be used to describe them. Therefore these descriptions can be used for reason- ing and automating their use such as automated discovery, selection and composition. In particular Web service com- position has triggered a considerable number of research ef- forts in the joint area of Semantic Web and Web service. Starting from an initial set of services, Web service compo- sition aims at selecting and inter-connecting services pro- vided by different partners according to a goal to achieve. Web service composition enhanced by semantic technolo- gies is currently one of the most addressed issues in the Service Oriented Computing. Most of the work in semantic Web services composi- tion has focused on two main levels of composition: func- tional [17, 11] and process [4, 20] levels (respectively FLC and PLC). The former level considers Web services as “atomic” components described in terms of their IOPEs (in- puts, outputs, preconditions, effects) and executed in a sim- ple request-response step. The latter level supposes services as stateful processes with an interaction protocol (i.e., be- haviour) involving different sequential, conditional, and it- erative steps. In such a level of description stateful services exposes their internal behaviours, and service composition aims at considering all distinct actions involved in Web ser- vices. Previous work in this regard has considered finite state machine (i.e., State Transition System STS [20]) or In- terface Automata [1] to model the internal and independent protocol of Web services [19, 15]. Even if the latter mod- els are appropriate to represent semantics of stateful Web services, some information is still missing to describe se- mantic enhanced Web services. In particular semantics on actions and their parameters involved in the whole protocol of Web services cannot be modelled. Indeed the semantics of actions is restricted to its feature of input, output or inter- nal action. Therefore it is not possible to apply any kind of reasoning on these syntactic descriptions. In this work, we introduce the semantic enhanced STS (S 2 TS from now) as a new way to model the internal behaviour of stateful services together with its data flow (well known as the assignment