Robotics Reference
In-Depth Information
commonsense reasoning. Thus Cyc is a kind of expert system,
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in which
the knowledge is employed by an inference engine in order to answer a
user's queries.
In April 2000 Lenat gave a demonstration of Cyc to officials from
the U.S. Department of Defense. At the request of one of the officials,
Lenat asked his program about anthrax, whereupon Cyc requested that
he clarify whether he meant the band,
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the bacterium, or the disease
caused by the bacterium? This somewhat surprising response illustrates
the breadth of Cyc's knowledge, but the program's next response was
even more surprising, and at the same time uncannily prescient. When
Lenat told Cyc that he meant the bacterium, and asked the program to
comment on its toxicity to people, Cyc's response included the prophetic
remark that one could use FedEx to mail packages containing anthrax
to high-ranking government officials. Eighteen months later the dreaded
bacterium started showing up in the mail.
Cyc's knowledge base consists of a vast quantity of fundamental hu-
man knowledge—facts and rules of thumb for reasoning about the ob-
jects and events of everyday life. Information is given to the program
using a formal language called CycL, which is far from ideal for every-
day users but which allows Cycorp's staff to impart knowledge to the
program in a format that it already understands. The knowledge itself
is made up of many thousands of “micro-theories”, each of which is es-
sentially a group of assertions that share a common set of assumptions.
Some of these micro-theories are focused on a particular knowledge do-
main, some on particular levels of detail, some on particular periods in
time. New knowledge is continually being added manually and in addi-
tion the system has the capability to automatically create facts from those
that it already knows, and to infer new facts.
Despite its apparently vast amount of knowledge and some impressive
examples of its capabilities, Cyc appears to be only scratching the surface
of the sum total of human knowledge. Partly prompted by this realisation
Push Singh, a PhD student of Marvin Minsky at the MIT Media Lab,
started the Open Mind Common Sense Project in the fall of 2000. Singh
has quantified commonsense knowledge thus:
Common sense is a problem of great scale and diversity. How big is
common sense? The scale of the problem has been terribly discour-
15
See the section “Expert Systems” later in this chapter.
16
The heavy metal rock group based in New York City.
