A grid workflow language using high-level petri nets

One approach to application programming for the Grid is to implement services with often-used functionality on high-performance Grid hosts and provide them to the users located at clients. Complex applications are created by using several services and specifying the workflow between them. We discuss how the workflow of Grid applications can be described in an intuitive way as a High-Level Petri Net (HLPN), in order to orchestrate and execute distributed applications on the Grid automatically. Petri Nets provide an intuitive graphical workflow description, which is easier to use than script-based descriptions and is much more expressive than directed acyclic graphs (DAG). In addition, the workflow description can be analysed for certain properties such as deadlocks and liveness, using standard algorithms for HLPNs. We propose a platform-independent, XML-based language, called Grid Workflow Description Language (GWorkflowDL), and show how it can be adapted to particular Grid platforms. As two example target platforms, we discuss Java/RMI and the current WSRF standard. 1