User-oriented partial result evaluation in workflow-based science gateways

Scientific workflow management systems provide a useful layer for defining and executing applications supported by science gateways. In various optimization or simulation applications that need to run for a long time, the users may be satisfied with an incomplete execution. The system should, therefore, allow users to evaluate partial results of the workflow execution. This entails performing a consolidation step, that would normally run only at the end of the workflow. In this paper, we present two new workflow patterns that formally define how the consolidation step should be executed (on partial inputs) whenever the user pro-actively requests evaluation of the partial results. This changes the traditional workflow behavior, in which every step runs once, when all its data dependencies are satisfied. We evaluate implementing these patterns in various workflow management systems and finally present a DIRAC-based implementation of this feature for the use case of a molecular docking gateway.