Synthesizing Constraint Expressions
A constraint network representation is presented
for a combinatorial search problem: finding 
values for a set of variables subject to a set of constraints.
 A theory of consistency levels in such 
networks is formulated, which is related to problems
of backtrack tree search efficiency.  An algorithm 
is developed that can achieve any level of consistency
desired, in order to preprocess the problem for 
subsequent backtrack search, or to function as an alternative
to backtrack search by explicitly determining 
all solutions.
CACM November, 1978
Freuder, E.C.
