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From: cje@topaz.RUTGERS.EDU (Ernst @ Sanctum Sanctorum)
Newsgroups: net.puzzle,net.math
Subject: Logic puzzle creation query
Message-ID: <4253@topaz.RUTGERS.EDU>
Date: Mon, 2-Dec-85 14:50:08 EST
Article-I.D.: topaz.4253
Posted: Mon Dec  2 14:50:08 1985
Date-Received: Thu, 5-Dec-85 05:00:39 EST
Organization: Rutgers Univ., New Brunswick, N.J.
Lines: 38
Xref: watmath net.puzzle:1218 net.math:2584

I'm looking for pointers to articles on the creation of a certain kind of
logic puzzle, specifically, the kind Martin Gardner calls 
"Smith-Jones-Robinson" puzzles.  These frequently involve a series of
propositions such as "The Englishman lives in the red house" or "Neither the
horse nor the dog is owned by the Norwegian".  You are then asked to provide
the answer to a question like "Who owns the zebra?"

I know how to *SOLVE* them, but I'd like to know how to *CREATE* them.  They
don't seem (to me) to be amenable to reverse engineering, plus there are a few
different types of these puzzles, presumably each with its own considerations.
I've seen puzzles in which people's names begin with A, B, C... and their
occupations start with a, b, c... and no one's occupation starts with the
same letter as his/her name.  I've seen "positional" puzzles, in which 
important clues are the relative positions of the various category members
(e.g., "The white house is on the immediate right of the green house"; "Milk
is drunk in the middle house").  I've seen puzzles in which you have males
and females and the clues run along the lines of "Neither Polly, the cat 
owner, nor Mr. Smith have a green car", which tells you that Smith is male 
(which wasn't known before) and that neither he nor Polly own the cat or the 
green car.

It seems to me that these puzzles involve something more than standard truth
table formulae, that is, the propositions are not usually of the form "If
P then Q".  So what form *ARE* they in?  (I am not a mathematician or 
logician, so if someone can tell me just how they *are* in truth table form,
I'd be interested.)  For x people and y categories, how do you know the 
minimum number of clues to provide to ensure the puzzle can be solved?  How 
do you know how often to mention any one category member (e.g., the white
house).

Again, I'm looking for pointers.  Logic texts, articles, citiations in
_Mathematical_Reviews_, etc., are all appreciated.  If the formulae are
relatively simple, and someone wants to mail them to me, I'd *really* 
appreciate it.

Chris Jarocha-Ernst
ARPA:   JAROCHA-ERNST@BLUE.RUTGERS.EDU
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