BOUML is a UML 2 tool box that allows you to specify and generate code in C++, Java, IDL, and PHP. BOUML is very fast and doesn't require much memory to manage several thousands of classes. BOUML is extensible, and the external tools (named plug-outs) can be written in C++ or Java, using BOUML for their definition as any other program. UML models can be exported to HTML pages, including PNG or SVG graphics.
Taverna is a collection of workflow enactment and description components, including a high level language for workflows called Scufl (Simple Conceptual Unified Flow Language), a pure Java object model, parser to populate the model, and a set of views and controllers (including some Swing components to drop into your workflow-enabled applications). In order to actually run workflows you also need the myGrid workflow enactment engine.