SWAMP is a java-based workflow engine. The workflows are defined in an XML format, with with focus on great flexibility and the possibility for quick and frequent changes.
The workflow engine is running on a central server, with a web-GUI and a SOAP interface for human interaction and for connecting it to other systems.
Zebra is a workflow engine - originally developed to fill in the gaps in some commercial and open source workflow engines. The key differences between it and other workflow systems are
* Able to model all the workflows described in workflow patterns
* An easy to use GUI designer
* Interfaced persistence layer
* OO Design
* Integration component for Turbine web applications
E. Sekerinski, and R. Zurob. &\#171;UML&\#187; '01: Proceedings of the 4th International Conference on The Unified Modeling Language, Modeling Languages, Concepts, and Tools, page 376--390. London, UK, Springer-Verlag, (2001)