Protégé is an Open Source ontology editor and knowledge-base framework. Although the core system is written in Java, plug-ins may be written in a variety of programming languages. The software may be used as an interactive workbench (e.g., editor, query tool) or as a knowledge-base server.
The Protégé platform supports two main ways of modeling ontologies:
- The Protégé-Frames editor enables users to build and populate ontologies that are frame-based, in accordance with the Open Knowledge Base Connectivity (OKBC) protocol. In this model, an ontology consists of a set of classes organized in a subsumption hierarchy to represent a domain's salient concepts, a set of slots associated to classes to describe their properties and relationships, and a set of instances of those classes - individual exemplars of the concepts that hold specific values for their properties.
- The Protégé-OWL editor enables users to build ontologies for the Semantic Web, in particular in the W3C's Web Ontology Language (OWL). "An OWL ontology may include descriptions of classes, properties and their instances. Given such an ontology, the OWL formal semantics specifies how to derive its logical consequences, i.e. facts not literally present in the ontology, but entailed by the semantics. These entailments may be based on a single document or multiple distributed documents that have been combined using defined OWL mechanisms" (see the OWL Web Ontology Language Guide).
Protégé has been under continuous development for more than two decades. It is being developed by Stanford Medical Informatics at the Stanford University School of Medicine. It is funded by several US Government agencies, as well as some affiliate organizations.