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NEW Aug2000: unabridged Cyc links
The history of AI has shown a gratifying series of successes in the realm of expert systems, all thru the 60s, 70s, and 80s.
The idea of expert systems is that expertise involves logical thinking, and can be modelled by compiling lists of logical propositions and performing logical transformations upon them. This might be called the "Euclidean (or geometric) model", implying a small set of axioms from which a wide range of theorems are then generated.
An alternative view might be called the "proverbs model". By this view, natural selection, over the course of geologic eons, has introduced millions of genetically-programmed details into the human nervous system, anticipating particular sorts of survival-challenges that may arise, and venturing effective ways of reacting to them. Compared to Euclid's geometry, there will be many more 'axioms' and relatively fewer 'theorems', so the logic will probably be comparatively trivial-- almost all the expertise will be in the data structures (and their contents). So once again, the Aristotle-problem is the real hurdle to expert-system development-- how do you concisely represent knowledge in a computer memory?
The Japanese Fifth Generation Project between 1982 and 1992 failed in its goals largely because it focused on logic, e.g. by choosing Prolog over LISP as its implementation language (a choice that may have been simple anti-Americanism, since Prolog was developed by the French).
Doug Lenat's Cyc (from enCYClopedia) Project at MCC in Austin, Texas, was begun in 1984 as a ten-year $35-million attempt to build a 'universal' expert system, able to understand and speak ordinary language, and detect violations of common sense as readily as humans can.
It took the first five of those years for the project to stabilize: basic questions about representing time, substances, perception, etc were resolved; the original emphasis on frames shifted heavily towards first-order predicate calculus instead; the idea of a unified knowledgebase was replaced with the idea of many partially-independent "micro-theories"; and a standard methodology for adding new knowledge was worked out.
A gif of Lenat and his partner, R.V. Guha:
As of 1994, CYC's sponsors were: Apple, Bellcore, DEC, the DOD, Interval, Kodak and Microsoft. Versions of CYC for Macs and Suns are supposed to be released this year.
Lenat has revised his estimate of the total number of 'rules' required for this, upward by a factor of ten (to 20-40 million), and extended the time needed by another ten years. It bothers me a lot that the sort of thing being added apparently includes rules like, "A creature with two arms probably has two legs." This seems out-of-control to me. CYC's ontology includes abstractions like:
Thing
Intangible
IndividualObject
Event
Stuff
Process
SomethingExisting
TangibleObject
A FAQ about Cyc, created by David Whitten, is now available in html format.
The Text Adventure Development System (TADS), by contrast, offers the following, much more pragmatic, partial object hierarchy:
Thing
Item: vehicle, surface, lightsource, key, food, container, clothing
FixedItem: switch, dial, button, decoration, actor, chair
Room
CYC's data-objects offer such slots as: instanceOf, inverse, makesSenseFor, entryIsA, specSlots, slotConstraints, becameTrueIn, qualitativeValue, sufficientCondition. One must expect that some of these slots will ultimately have thousands of fillers, requiring hash- tables and slowing processing proportionately, and that some objects will have thousands of slots, causing similar problems. Interestingly, in a recent interview Lenat claimed that the number of facts has been at a plateau lately, even as the amount of useful knowledge continues to grow, because various redundancies in the representation are also being detected and repaired.
Lenat, at some point, asked John McCarthy to take a shot at enumerating the laws of human emotion, a critical challenge for the project as a whole. I don't know where this led (although Lenat claims CYC now 'knows' about emotions), but McCarthy could have done worse than to start with Andrew Ortony's dimensional analysis of emotions. Ortony's classes of emotion:
Emotions about things: liking, disliking.
Emotions about persons: approving, disapproving.
about self: pride, shame.
about others: admiration, reproach.
Emotions about events for self: pleasing, displeasing.
for other: gloating, pity, resentment, happy-for.
about events in the future: hope, fear.
realized (positive): satisfaction, relief.
realized (negative): disappointment, fears-confirmed.
Emotions about another person's role in events: gratitude, anger.
about self's role: 'gratification', remorse.
Another admirable style of 'Aristotelian' thinking about whole systems can be found in an obscure anthropology text called "Man's Place in Nature" by C.F. Hockett (McGraw-Hill 1973). Hockett is a fearlessly original thinker, always striving to find the apt generalization behind the variations of cultures in history. For example, a series of generalizations about techniques of primitive peoples for strengthening the surfaces of their artifacts is characterized with the motto: "Save the surface and you save all." (This is AI at its best!)
comp.ai.shells newsgroup
The Expert Systems Shells FAQ is also available by anonymous ftp from
the same ftp location as the comp.ai.status-quo FAQ (see biblio at end).
CYC/MCC's presence on the Net is unfortunately very low-profile. There was an excellent Nova (?) program about it, in a series on the computer. The Machine That Changed The World
A report on Cyc by a skeptic Here's some periodical references, and the only book so far:
There's an interesting account of Lenat's previous program, Eurisko, in George Johnson's "Machinery of the Mind". More info is at his WWWeb site.
Andrew Ortony, Clore and Collins: "The Cognitive Structure of
Emotions" (about $12 paper from Cambridge U.P.)
An implementation of this theory as an a-life microworld is described
in: Elliott: The Affective Reasoner (the TaxiWorld thesis, TR#32).
It can be ordered for a few
dollars from ILS.
The brand-new "Wisdom FAQ" mailing list
(wisdom-request@mcs.com) is a first stab at an Internet
version of the CYC project, aimed at creating a comparable public
domain knowledgebase especially for interactive fiction (IF) and
social simulations. Its archives are at
ftp://ftp.mcs.com/mcsnet.users/jorn/wisdom/.