Christian Nentwich has created BOX, a tool that takes UML diagrams in XMI format and renders them in either SVG or Microsoft's VML format.

Nentwich warns that "the state of the code is rather embarrassing and there is no-one to maintain it, so I hesitated for quite a while." He also describes the modelling tools required to use his code:

Since diagram information in XMI is (so far) proprietary, the tools requires you to use the Unisys exporter for Rational Rose (or Select Enterprise). It uses simple heuristics to restore the diagrams from the rather poor info the exporter makes available.

In addition to the rendering functionality, Nentwich's code can produce DTDs from UML models -- a topic attracting increasing interest and debate.