  This paper studies peek arc consistency, a reasoning technique that extends
the well-known arc consistency technique for constraint satisfaction. In
contrast to other more costly extensions of arc consistency that have been
studied in the literature, peek arc consistency requires only linear space and
quadratic time and can be parallelized in a straightforward way such that it
runs in linear time with a linear number of processors. We demonstrate that for
various constraint languages, peek arc consistency gives a polynomial-time
decision procedure for the constraint satisfaction problem. We also present an
algebraic characterization of those constraint languages that can be solved by
peek arc consistency, and study the robustness of the algorithm.
