API Reference for UML Modeling Extensibility
You can write program code to read and modify the models that you create with Visual Studio. The API reference provides information about the specific classes to help you with this. For more task-oriented information, see the topics under Extend UML models and diagrams. To see which versions of Visual Studio support UML models, see Version support for architecture and modeling tools.
What this allows you to do
The namespaces and types correspond to those that are defined in the UML Specification.