demon: n. 1. [MIT] A portion of a program that is not invoked explicitly,

:demon: n. 1. [MIT] A portion of a program that is not invoked
explicitly, but that lies dormant waiting for some condition(s) to
occur. See {daemon}. The distinction is that demons are
usually processes within a program, while daemons are usually
programs running on an operating system. 2. [outside MIT] Often used
equivalently to {daemon} --- especially in the {{UNIX}} world,
where the latter spelling and pronunciation is considered mildly
archaic.

Demons in sense 1 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.
-- The AI Hackers Dictionary