A-GWL: Abstract Grid Workflow Language

Grid workflow applications are emerging as one of the most interesting application classes for the Grid. In this paper we present AGWL, a novel Grid workflow language to describe the workflow of Grid applications at a high level of abstraction. AGWL has been designed to allow the user to concentrate on describing scientific Grid applications. The user is shielded from details of the underlying Grid infrastructure. AGWL is XML-based which defines a graph of activities that refers to computational tasks or user interactions. Activities are connected by controland data-flow links. We have defined AGWL to support the user in orchestrating Grid workflow applications through a rich set of constructs including sequence of activities, sub-activities, control-flow mechanisms (sequential flow, exclusive choice, and sequential loops), data-flow mechanisms (input/output ports), and data repositories. Moreover, our work differs from most existing Grid workflow languages by advanced workflow constructs such as parallel execution of activities with preand post-conditions, parallel loops, event-based synchronization mechanisms, and property-based selection of activities. In addition, the user can specify high-level constraints and properties for activities and data-flow links.