Overview of CYC
The CYC project is the first serious attempt to build a base of human consensus knowledge -- to encode common sense. The CYC system is intended to provide a "deep" layer of understanding that can eventually be used by other programs to make them more flexible and less "brittle".
This paper discusses of the motivations behind the encoding of common sense, provides an overview of the CYC system and touches on some of its applications.
Often it is enough is to solve problems in a very specific domain. Expert systems are often called upon when this type of intelligence is desired. Knowledge based systems have enjoyed commercial success and have shown promise as candidates for practical intelligent systems of the near future .
Traditional knowledge based systems -- and programs in general -- have an undesirable performance characteristic that can be described as brittleness. The term -- coined by Doug Lenat -- refers to software, which when given well conditioned data, will produce acceptable results, but when confronted by some unanticipated situation, is likely to reach the wrong conclusion. This brittleness arises because knowledge based systems lack the common sense that all humans possess. Lenat laments that
"It is all too easy to find examples of such brittle behavior: a skin disease diagnosis system being told about a rusty old car, and concluding it has measles; a car loan authorization system approving a loan from someone whose ``years at the same job'' exceeded their age; a digitalis dosage system that doesn't complain when someone accidentally types a patient's age and weight in reverse order (even though this 49 pound, 102 year old patient was admitted to the hospital by their mother); and so on." 
The proposed solution to this software brittleness bottleneck is to develop an AI with common sense. While traditional expert system has very detailed knowledge of a limited area, there is a need for a system with a limited amount of knowledge of many areas. This common sense would provide a set of first principles to fall back on when a new situation arises, and allows filling in the gaps in knowledge of an expert system.
The CYC project is the first serious attempt to build a base of human consensus knowledge. The CYC system is intended to provide a "deep" layer of understanding that can eventually be used by other programs to make them more flexible and less brittle .
CYC is an attempt to do symbolic AI on a massive scale. It is not based on numerical methods such as statistical probabilities, nor is it based on neural networks or fuzzy logic. All of the knowledge in CYC is represented declaratively in the form of logical assertions. New conclusions are derived by the inference engine using deductive reasoning.
CYC was originally developed at the Microelectronics and Computer Technology Corporation (MCC) in Austin, Texas in 1984. CYC is now being developed...