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Lookup NU author(s): Dr Simon Woodman, Douglas Palmer, Emeritus Professor Santosh Shrivastava, Dr Stuart Wheater
Availability of a wide variety of Web services over the Internet offers opportunities of providing new value added services built by composing them out of existing ones. Service composition poses a number of challenges. A composite service can be very complex in structure, containing many temporal and data-flow dependencies between their constituent services. Furthermore, each individual service is likely to have its own sequencing constraints over its operations. It is highly desirable therefore to be able to validate that a given composite service is well formed: proving that it will not deadlock or livelock and that it respects the sequencing constraints of the constituent services. With this aim in mind, the paper proposes simple extensions to web service definition language (WSDL) enabling the order in which the exposed operations should be invoked to be specified. In addition, the paper proposes a composition language for defining the structure of a composite service. Both languages have an XML notation and a formal basis in the pi-calculus (a calculus for concurrent systems). The paper presents the main features of these languages, and shows how it is possible to validate a composite service by applying the pi-calculus reaction rules.
Author(s): Woodman SJ, Palmer DJ, Shrivastava SK, Wheater SM
Publication type: Report
Publication status: Published
Series Title: School of Computing Science Technical Report Series
Year: 2004
Pages: 12
Print publication date: 01/06/2004
Source Publication Date: June 2004
Report Number: 849
Institution: School of Computing Science, University of Newcastle upon Tyne
Place Published: Newcastle upon Tyne
URL: http://www.cs.ncl.ac.uk/publications/trs/papers/849.pdf
