Abstract Workflow Description Language

Currently, scientific application developers often configure available application components into a workflow of tasks that they can submit for execution on distributed systems. In this chapter, we present the Abstract Workflow Description Language (AWDL) for describing scientific workflow applications at a high level of abstraction. AWDL has been designed such that the user can concentrate on specifying scientific applications without dealing with either the complexity of distributed systems or any specific implementation technology (e.g., Web Services). AWDL is an XML-based language which allows a programmer to define a graph of activities that refer mostly to computational tasks. Activities are connected by control and data flow links. A rich set of control flow constructs (compound activities) is provided to simplify the specification of scientific workflow applications which includes dag, for, while, and alt. In addition, AWDL programmers can specify high-level constraints and properties for activities and data flow links which may be useful for underlying runtime systems to steer and optimize workflow executions. AWDL is the main interface to the ASKALON development and runtime environment for workflows on distributed systems and has been applied to numerous real-world scientific workflow applications. We describe a material science workflow that has been successfully ported to a distributed infrastructure based on the AWDL specification.