CycL

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CycL in computer science and artificial intelligence, is an ontology language used by Douglas Lenat's Cyc artificial intelligence project. Ramanathan V. Guha was instrumental in designing early versions of the language. A close CycL variant exists named MELD.^[1]

The original version of CycL was a frame language, but the modern version is not. Rather, it is a declarative language based on classical first-order logic, with extensions for modal logic operators and higher-order logic quantification.

CycL is used to represent the knowledge stored in the Cyc Knowledge Base, available from Cycorp. The source code written in CycL released with the OpenCyc system is licensed as free and open-source software, to increase its usefulness in supporting the semantic web.