Cyc is a project begun MCC and spun off into its own company, with the
aim to build an enCYClopedic database and reasoning engine for common
sense knowledge.  There is now an open source version of Cyc. See
section 6 of the FAQ.

   Lenat, D. B. "Cyc: A Large-Scale Investment in Knowledge
   Infrastructure." Communications of the ACM 38, no. 11 (1995)

   Lenat, D. B. "Steps to Sharing Knowledge." In Toward Very Large
   Knowledge Bases, edited by N.J.I. Mars. IOS Press, 1995.

   R.V. Guha and Douglas B. Lenat, "Enabling agents to work together",
   CACM 37(7):127-142, 1994.

   "CYC", AI Magazine 1986, 7(1), 1986.

   "Cyc: A Mid-Term Report," AI Magazine, 11(3):32-59, Fall 1990.

   "Cyc: Toward Programs With Common Sense," CACM, 33(8):30-49, 
   August 1990. 

   "Knowledge and Natural Language Processing," CACM, Aug 1990.
 
   "When will machines learn?," Machine Learning, 4(3-4):255-257,
   December 1989. 

   Douglas B. Lenat and R.V. Guha, "Building Large Knowledge-Based
   Systems", Addison-Wesley, Reading, MA, 1990. ISBN 0-201-51752-3.

For a critique of Cyc, see Stefik and Smoliar, "The Commonsense
Reviews", Artificial Intelligence 61(1):37-40 1993.