yEd Graph Editor
yEd is a powerful diagram editor that can be used to quickly create diagrams manually or import external data for analysis and auto-magically arrange even large data sets by just pressing a button.
Protégé is a free, open source ontology editor and knowledge-base framework. The Protégé platform supports two main ways of modeling ontologies...
protégé is a free, open source ontology editor and knowledgebase framework.
the protégé platform supports two main ways of modeling ontologies via the protégéframes and protégéowl editors. protégé ontologies can be exported into a variety of formats including rdf(s), owl, and xml schema. (more)
protégé is based on java, is extensible, and provides a plugandplay environment that makes it a flexible base for rapid prototyping and application development. (more)protégé is supported by a strong community of developers and academic, government and corporate users, who are using protégé for knowledge solutions in areas as diverse as biomedicine, intelligence gathering, and corporate modeling.
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java-based rdf ontology owl