As it is required to handle UML data, a choice of interchange format has to be made. The role of an interchange format is to standardize generation templates whichever UML CASE tool is used. A standard format could be OMG's XMI, but unfortunately it leads to a lot of incompatibilities among CASE tools, does not handle diagrams, and moreover it is rather complex and it is not easy to handle with tools. For ULM.gen, the choice has been made to use a simple XML format which can be easily mapped to scripting languages such as Python. And in case you prefer the use of XMI, it is possible to develop XSL stylesheets that transform XMI documents into the ULM.gen specific format.

The ULM.gen XML format is based on the ULM.gen meta-model (UMM) which is described as a first-level component.