Cyc Knowledge Base is a formalized representation of a vast quantity of fundamental human knowledge: facts, rules of thumb, and heuristics for reasoning about the objects and events of everyday life.

• Cyc Wikipedia article
• CycL is the formal language used for knowledge representation
• OpenCyc is the open source version of the Cyc technology
• ResearchCyc has the complete (non-proprietary) content of the Cyc knowledge base

Cyc contains 10s of thousands of predicates, 100s of thousands of concepts and millions of assertions (as of 2006).

Knowledge hiereachy: Upper ontology -> Core theories -> Domain-specific theories -> very specific information

Inference engine consist of 1000 agents that attack every problem & sub-problem

Cyc does not provide definitive proofs: only arguments for and against

Architecture:

• UI - query by people
• Knowledge entry tools - input
• API - query by applications
• External datasources (web pages, other KBs, etc) - machine input

Reasoning: deduction, abduction (inference in reverse) and induction

Public versions:

• OpenCyc - vocabulary of 100,000s terms
• ResearchCyc - everything