High-level composition of QoS-aware Grid workflows: An approach that considers location affinity

At a high level of abstraction grid applications are commonly specified based on the workflow paradigm. We consider that for the wide acceptance of grid technology it is relevant that the user has the possibility to express requirements on quality of service (QoS) at workflow specification time. However, most of the existing workflow languages lack constructs for QoS specification, or provide only limited QoS support. In this paper we present an approach for high level workflow specification that considers a comprehensive set of QoS requirements. Besides performance related QoS, it includes economical, legal and security aspects. For instance, for security or legal reasons the user may express the location affinity regarding grid resources on which certain workflow tasks may be executed. Our QoS aware workflow system provides support for the whole workflow life cycle from specification to execution. Workflow is specified graphically, in an intuitive manner, based on a standard visual modeling language. We illustrate our approach with a real world workflow for maxillo facial surgery simulation.