There is only one file type that uses the .UXF extension:
UML eXchange Format
A UXF file is a model interchange file saved in the UML eXchange Format (UXF). It contains Unified Modeling Language (UML) elements in XML format that make up a diagram. UML files are commonly used in the software engineering field to visualize the structure of an application or system.
Updated: December 15, 2017