Overview

Modern application architecture and design practices recommend the concept of "composition" (of existing modules and components) in the assembly of an overall application, to maximize the resuse of previously built functionality. However, it is still generally necessary to write original code that "glues" the components together. It would be useful if individuals familiar with the business requirements of their systems could create "scripts" to represent the linkages between components, rather than requiring Java code. The Workflow proposal intends to create support for just such a capability.

Scripted workflows is an idea that can be used in many different application environments and use cases. In particular, a highly desired use is in managing the interaction with web application users, where the transaction being performed requires more than one HTML page to be displayed. However, the Workflow implementation will be strictly layered so that the underlying scripting engine can be used without any reliance on web layer APIs

The Workflow project shall create and maintain an engine to manage and execute scripts, codified in XML. The basic engine shall be environment independent, but specialized implementations of the basic engine can adapt the engine to that environment.

One specialized implementation will be included in the Workflow package itself - an adapter to integrate the workflow engine into the web layer, by mapping the Workflow concept of bean scopes into the scopes provided by the Servlet API (request, session, and application). This implementation will be independent of any particular web application framework - it is expected that frameworks will further specialize the web layer implementation in order to integrate the framework's own capabilities and features.

Scripts for the workflow engine will be codified in XML. It shall be possible for specialized implementations to register their own sets of custom Step implementations, under a specific XML namespace, to transparently extend the set of built in Step implementations that is available to workflow engine users.