Notes about the UML file extension:
Incorrect file associations could be the result of underlying issues within your PC system. As such it is highly recommended to scan your PC for invalid registry entries, unused processes and other unfavourable system settings to identify slowdown issues.
The UML file type is primarily associated with 'Visual UML' by Visual Object Modelers, Inc.. Object modeling tool that provides support for all of the OMG UML (Unified Modeling Language) 1.3 & 1.4 diagram types: Use Case, Package, Class, Object, Activity, State, Collaboration, Sequence, Component, Deployment and Robustness diagrams.