Activity pre-scheduling for run-time optimization of grid workflows

The capability to support resource sharing between different organizations and high-level performance are noteworthy features of grid computing. Applications require significant design effort and complex coordination of resources to define, deploy and execute components on heterogeneous and often unknown resources. A common trend today aims at diffusing workflow management techniques to reduce the complexity of grid systems through model-driven approaches that significantly simplify application design through the composition of distributed services often belonging to different organizations. With this approach, the adoption of efficient workflow enactors becomes a key aspect to improve efficiency through run-time optimizations, so reducing the burden for the developer, who is only responsible of defining the functional aspects of complex applications since he/she has only to identify the activities that characterize the application and the causal relationships among them. This paper focuses on performance improvements of grid workflows by presenting a new pattern for workflow design that ensures activity pre-scheduling at run-time through a technique that generates fine-grained concurrency with a couple of concepts: asynchronous invocation of services and continuation of execution. The technique is implemented in a workflow enactment service that dynamically optimizes process execution with a very limited effort for application developer.