CycL First-Order Logic Language

AKA: CycL.
See: Semantic Web, Artificial Intelligence, Ontology Language, Doug Lenat, Cyc, List of Notable Artificial Intelligence Projects, Ramanathan V. Guha, Frame Language, Declarative Language, First-Order Logic, Modal Logic.

References

(Wikipedia, 2017) ⇒ https://en.wikipedia.org/wiki/CycL Retrieved:2017-6-11.
- CycL in computer science and artificial intelligence is an ontology language used by Doug Lenat's Cyc artificial intelligence project. Ramanathan V. Guha was instrumental in the design of early versions of the language. There is a close variant of CycL known as MELD.
  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 operators and higher order 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 open source, to increase its usefulness in supporting the semantic web.

(Cycorp, 2017) ⇒ "CycL: The Cyc Knowledge Representation Language" http://www.cyc.com/cycl/ Retrieved:2017-6-11.
- CycL is Cyc’s large and extraordinarily flexible knowledge representation language. It is essentially an augmentation of first-order predicate calculus (FOPC), with extensions to handle equality, default reasoning, skolemization, and some second-order features. (For example, quantification over predicates is allowed in some circumstances, and complete assertions can appear as intensional components of other assertions.) CycL uses a form of circumscription, includes the unique names assumption, and can make use of the closed world assumption where appropriate.

(Cycorp, 2017) ⇒ "Cycl Syntax" http://www.cyc.com/cycl/syntax/ Retrieved:2017-6-11.
- CycL is a formal language whose syntax derives from first-order predicate calculus (the language of formal logic) and from Lisp. In order to express common sense knowledge, however, it goes far beyond first order logic. The vocabulary of CycL consists of terms. The set of terms can be divided into constants, non-atomic terms (NATs), variables, and a few other types of objects. Terms are combined into meaningful CycL expressions, which are used to make assertions in the Cyc knowledge base. (...)