demon
1. <operating system> (Often used equivalently to daemon, especially in
the Unix world, where the latter spelling and pronunciation is considered mildly
archaic). A program or part of a program which is not invoked explicitly, but
that lies dormant waiting for some condition(s) to occur.
At MIT they use "demon" for part of a program and "daemon" for an operating
system process.
Demons (parts of programs) are particularly common in AI programs. For example,
a knowledge-manipulation program might implement inference rules as demons.
Whenever a new piece of knowledge was added, various demons would activate
(which demons depends on the particular piece of data) and would create
additional pieces of knowledge by applying their respective inference rules to
the original piece. These new pieces could in turn activate more demons as the
inferences filtered down through chains of logic. Meanwhile, the main program
could continue with whatever its primary task was. This is similar to the
triggers used in relational databases.
The use of this term may derive from "Maxwell's Demons" - minute beings which
can reverse the normal flow of heat from a hot body to a cold body by only
allowing fast moving molecules to go from the cold body to the hot one and slow
molecules from hot to cold. The solution to this apparent thermodynamic paradox
is that the demons would require an external supply of energy to do their work
and it is only in the absence of such a supply that heat must necessarily flow
from hot to cold.
Walt Bunch believes the term comes from the demons in Oliver Selfridge's paper
"Pandemonium", MIT 1958, which was named after the capital of Hell in Milton's
"Paradise Lost". Selfridge likened neural cells firing in response to input
patterns to the chaos of millions of demons shrieking in Pandemonium.
2. <company> Demon Internet Ltd.
3. A program generator for differential equation problems.
[N.W. Bennett, Australian AEC Research Establishment, AAEC/E142, Aug 1965].
[Jargon File]
(1998-09-04)
Nearby terms:
demodulate « demodulation « demo mode « demon
» Demon Internet Ltd. » DeMorgan's theorem » demo
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