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From: marcel@uiucdcs.UUCP (marcel )
Newsgroups: net.ai
Subject: a trivial reasoning problem? - (nf)
Message-ID: <4713@uiucdcs.UUCP>
Date: Tue, 27-Dec-83 22:25:11 EST
Article-I.D.: uiucdcs.4713
Posted: Tue Dec 27 22:25:11 1983
Date-Received: Fri, 6-Jan-84 01:44:37 EST
Lines: 27

#N:uiucdcs:32300014:000:919
uiucdcs!marcel    Dec 27 16:23:00 1983

Here's a problem I'd like some comments on. As far as I know this problem is
not solvable using regular Horn clause logic (see my note on net.lang.prolog).
If you have an inference engine capable of solving it, please tell me about
it; otherwise, please let me know why its difficult. The problem is of my own
devising.

	Suppose you are shown two lamps, 'a' and 'b', and you
	are told that, at any time,

		1. at least one of 'a' or 'b' is on.
		2. whenever 'a' is on, 'b' is off.
		3. each lamp is either on or off.
	
	WITHOUT using an exhaustive generate-and-test strategy,
	enumerate the possible on-off configurations of the two
	lamps.

If it were not for the exclusion of dumb-search-and-filter solutions, this
problem would be trivial. The exclusion has left me baffled, even though
the problem seems so logical.

					Marcel Schoppers
					U of Illinois at Urbana-Champaign
					{pur-ee|ihnp4}!uiucdcs!marcel