Workflow is becoming extremely important within course grained distributed system models for e-Science applications. As the technological backbone of the Grid infrastructure is becoming standardised, scientists are in need of the ability to specify flows of control within the chains of applications that constitute their experiments. This is a timely book that presents an overview of the current state of the art within established projects, presenting many different aspects of workflow from users to tool builders. This book aims to provide a broad overview of active research, from a number of different perspectives e.g. from application requirements to representations, infrastructures and tools for aiding the workflow composition process. The topics covered represent a broad range of aspects of workflow and will be of interest to a wide range of practitioners, from computational experimentalists in the multitude of e-Science fields, to the computer scientists and engineers within Grid and peer-to-peer computing.