An optimal arc consistency algorithm AC-4 was given by R. Mohr and T.C. Henderson (1986). AC-4 has costO(ea/sup 2/), and cost(na/sup 2/) for scene labeling. Although their algorithm is indeed optimal, under certain conditions a constraint satisfaction problem can be transformed into a less complex problem. Conditions and mechanisms are presented for such transformations, and it is shown how to factor relations into more manageable components. A description is given of how factorization can reduce AC-4's cost to O(ea), and this result is applied to RETE match. >
['Mark W. Perlin']
Arc consistency for factorable relations