Tech Reports

ULCS-10-009

An XML Mapping Language for Dynamic Semantic Workflow Harmonisation

Martin Szomszor, Terry R. Payne and Luc Moreau

Abstract

Service-oriented architectures have evolved to support the composition and utilisation of heterogeneous resources, such as services and data repositories, whose deployment can span both physical and organisational boundaries. The Semantic Web Service paradigm facilitates the construction of workflows over such resources using annotations that express the meaning of the service through a shared conceptualisation. While this aids non-expert users in the composition of meaningful workflows, sophisticated middle-ware is required as service providers and consumers often assume different data formats for conceptually equivalent information. When syntactic mismatches occur, some form of workflow harmonisation is required to ensure that data format incompatibilities are resolved, a step we refer to as syntactic mediation. Current solutions are entirely manual; users must consider the low-level (i.e. data format) interoperability issues and insert Type Adaptor components into the workflow by hand, contradicting the Semantic Web Service ideology. By exploiting the fact that services are connected together based on shared conceptual interfaces, it is possible to associate a canonical data model with these shared concepts, providing the basis for workflow harmonisation through an intermediary data model. To investigate this hypothesis, we have developed a formalism to express the mapping of elements between data models in a modular and composable fashion that facilitates mapping reuse. We present our mapping language (fxmlm) and give both its precise semantics, the rules that define the transformation process they dictate, and present an evaluation of an implementation of the approach with respect to other mapping mechanisms.

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