R. Baird and R. Gamble, “Architecting a Delta-Federation”, accepted to IEEE World Congress on Services (SERVICES), 2009.
Dynamic composition-based systems provide powerful computational sources and data sets for knowledge and information processing. Integrating disparate components from various providers on demand is plagued with interoperability and quality of service problems that encompass functional, non-functional, and semantic concerns. The barriers to achieving integration are lack of encapsulating community needs, limited sharing of task coordination, computation, and results, lack of connectivity among resources, unstructured information, and changes in the access, availability, and functionality of providers. A novel framework for development is needed to realistically address these issues. We define a Delta-Federation as a community-centric, layered infrastructure that contracts to integrate resources for on demand use within a particular context. The goal of the Delta-Federation is to formulate dynamic, yet sharable workflows within a community of interest.
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M. Hepner, R. Baird, and R. Gamble, “Dynamically Changing Workflows of Web Services”, accepted to IEEE Int’l Workshop on Web Service Composition and Adaptation (WSCA), 2009.
Incorporating dynamism in web service workflows should adapt instance execution as services change availability. Workflow reconfiguration traditionally modifies only workflows but not instances, which does not address dynamic execution change management. Commercial workflow engines lack mechanisms to adapt instances except where instances deploy with all possible workflow paths, to achieve pseudo-dynamism. This method is error prone, has the potential for unsound specifications and does not allow runtime modifications. We achieve workflow reconfiguration through an inspection-feedback loop that allows users to express redundant services within BPEL workflows. We formally specify the architecture according to its separation of concerns with respect to reconfiguration activities. We prove the direct migration of a workflow instance when a service becomes unavailable and the system designates an alternative service for execution.
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