A very important topic in the effort of deploying workflow applications in grid environments is finding a means to describe the complex application structures that is simple for users yet expressive enough to provide the workflow scheduler with the information needed to make (good) scheduling decisions. A workflow description language defines syntax and semantics for specifying workflow tasks and their relationships; thus it provides an abstract and formalized representation of the complex workflow structures in text format. But the existing workflow description languages focus on expressiveness with respect to describing the data and control flow of workflow structures. They lack the ability to specify resource request information in support of resource allocations for workflow tasks by the scheduler. In addition, we have found that many of the features requested by end users are not, or are only partially supported in current workflow languages.

In this paper, we present a high-level abstract language for domain scientists to describe workflow applications in grid environments, the Grid Application Modeling and Description Language (GAMDL). GAMDL associates resource request information with a workflow description so that a workflow scheduler can make resource co-allocation requests based only on the workflow description itself. In terms of expressiveness, GAMDL is able to describe data-flow structures of complex domain problems, and also allows the definition of control-flow logic within the data-flow. Designed to be intuitive and suitable for users without a background in grid computing, GAMDL provides features that are not available in other languages.