On 9 March 2004 the Global Grid Forum (GGF) hosted a workshop on the topic of workflow in Grid systems. Our goal in organizing this workshop was twofold. First, we wanted to survey and contextualize the very large spectrum of work already going on within the Grid research community on workflow programming and enactment [1]. Second, and perhaps more importantly, we wished to understand and to articulate the major problems that remain to be solved in this area. If the GGF community can bring some clarity to these outstanding research themes, we may be able to help focus the community on solutions.
The fact that the Grid research community has such a strong desire to define the role of workflow in Grid systems may come as some surprise to people in the business world. The Workflow Management Coalition (WfMC) has existed for over 10 years and they have standard reference models, documents and a substantial industry of tools and workflow management support products. Why has the Grid community not adopted these existing standards? While it is not uncommon for the scientific community to re-invent technology rather than purchase existing solutions, there are issues involved in the technical applications of Grid systems that are unique to science and go beyond the models of workflow of the past. For example, in 1996 the WfMC defined workflow as:
'The automation of a business process, in whole or part, during which documents, information or tasks are passed from one participant to another for action, according to a set of procedural rules ' [2].
Clearly, this definition does not accurately capture the current business world, which is in the process of being transformed by the needs of e-commerce and a move to Web services. In the case of workflow in science and engineering, the primary topic of the papers here, workflow concepts have evolved from distributed programming using systems such as Linda [3], AVS [4] and Khoros [5] and complex shell scripts to a suite of sophisticated programming systems described below. Similarly, the Grid world has evolved from simple toolkits to authenticate users on remote supercomputers, to a service-based