Using a Functional Language as Embedding Modeling Language for Web-Based Workflow Applications

Workflow management systems guide and monitor tasks performed by humans and computers. Workflow specifications are usually expressed in special purpose (graphical) formalisms. These models are concise and made rapidly. These formalisms commonly have as disadvantage that they have limited expressive power, handle only rather static workflows, do not handle intricate data dependencies, and cannot easily adapt to the current situation. Furthermore, workflow specification tools mostly generate a software infrastructure that needs to be extended with custom crafted code. To overcome these problems, we entirely embed a workflow modeling language in a modern general purpose functional language, and generate a complete workflow application. We have developed the iTask prototype system in the pure and lazy language Clean. An iTask workflow specification can use the expressive power and strong type facilities of Clean. Workflows can be higher-order and adapt their behavior based on the available data. The generated application is web-based and runs on both server and clients.