Protégé is a free, open source ontology editor and knowledge-base framework.
The Protégé platform supports two main ways of modeling ontologies via the Protégé-Frames and Protégé-OWL editors. Protégé ontologies can be exported into a variety of formats including RDF(S), OWL, and XML Schema.
Protégé is based on Java, is extensible, and provides a plug-and-play environment that makes it a flexible base for rapid prototyping and application development.
The OntoLT approach aims at a more direct connection between ontology engineering and linguistic analysis. OntoLT is a Protégé plug-in, with which concepts (Protégé classes) and relations (Protégé slots) can be extracted automatically from linguistically annotated text collections. It provides mapping rules, defined by use of a precondition language that allow for a mapping between linguistic entities in text and class/slot candidates in Protégé.
Our goal is to develop a probabilistic knowledge base that mirrors the content of the web. We are developing a system that uses semi-supervised learning methods to learn to extract symbolic knowledge from unstructured text and HTML. We are exploring methods of continous learning, where our system runs 24x7, continuously learning to read better, and continuously extracting facts from the web.
ConceptNet represents data in the form of a semantic network, and makes it available to be used in natural language processing and intelligent user interfaces.
OpenCyc is the open source version of the Cyc technology, the world's largest and most complete general knowledge base and commonsense reasoning engine.
P. Pantel, and M. Pennacchiotti. Ontology Learning and Population: Bridging the Gap between Text and Knowledge, volume 167 of Frontiers in Artificial Intelligence and Applications, IOS Press, (2008)
M. Vargas-Vera, and D. Celjuska. WI '04: Proceedings of the 2004 IEEE/WIC/ACM International Conference on Web Intelligence, page 615--618. Washington, DC, USA, IEEE Computer Society, (2004)