DECS: A System for Decentralised Coordination of Web Services

Web Services technology is becoming the de-facto standard for integration of legacy applications within an organisation and for cross organisation enterprise application integration. Much work has gone into specifying Web Services functionality using workflow like techniques and production of software to enact such descriptions. However, most of this software relies on one central server to enact the workflow. Centralised enactment may be unattractive in inter-organisational settings and in addition, form a performance bottleneck when the server is under high load. In this paper we outline the DECS task model for workflow specification and present a prototype implementation of a distributed enactment engine based on J2EE middleware. There is a separation of concerns between the specification of the workflow and its enactment, allowing it to be deployed in a number of configurations based on performance considerations and organisational requirements. We also describe how the workflow engine promotes message based integration, simplifying the problem of application integration across organisational boundaries.