Preferential Refinements of Abstract State Machines for Service Mediators

Large-scale service-oriented computing is based on the idea that services from various servers are combined into one distributed application. For this the notion of service mediator has been coined, which captures specifications of composed services with slots that have to be filled by actual services. Such mediators can be specified by expressions in Kleene algebras with tests (KATs) or equivalently by very restricted Abstract State Machines (ASMs). In this paper we address the refinement of such specifications with the intention to capture more meaningful conditions on the service slots and to fine-tune the matching of the slots with actual services. In particular, we investigate refinements that express user preferences thus leading to personalised mediators. For this form of adaptivity a previously developed term rewriting approach on KATs is generalised to refinements on ASMs.