Protégé is a free, open source ontology editor and a knowledge management system.
The Protégé meta-tool was first built by Mark Musen in 1987 and has since been developed by a team at Stanford University.
It also includes deductive classifiers to validate that models are consistent and to infer new information based on the analysis of an ontology.
This application is written in Java and makes heavy use of Swing to create the user interface.
[9] Earlier versions of the tool were developed in collaboration with the University of Manchester.