Building Blocks for Workflow System Middleware

We suggest there is a need for a fresh perspective on the design and development of middleware for high-performance workflows and workflow systems. We argue for a building blocks approach, outline a description of this approach and define their properties. We discuss RADICAL-Cybertools as one implementation of the building blocks concept, showing how they have been designed and developed in accordance with this approach. We discuss three case-studies where RADICAL-Cybertools have been used to develop new workflow systems capabilities and in-tegrated to enhance existing ones, illustrating the potential and promise of the building blocks approach.