Dynamic Workflow Implementation Based on Synchronizers

The paper presents how parallel program execution control based on monitoring of global application states can be used to co-ordinate workflow execution. Special control processes called synchronizers construct consistent application states based on state messages coming from constituent workflow activities. The synchronizers compute control predicates on consistent activities states and work out control decisions concerning workflow behavior. The decisions are dispatched as control signals to workflow elements. The reactions to the signals correspond to workflow tasks activations or modifications by a mechanism similar to distributed interrupts. This mechanism provides for dynamic character of workflow elements and control, which can be applied in arranging groupware applications. Such workflow control can be implemented inside the PS-GRADE graphical parallel program design system, which is described in the paper. PS-GRADE enables designing programs for both computer clusters and grids. An overview of workflow control patterns implemented with the use of the proposed new control mechanisms is shown and discussed in the paper