Martelli, A. | Montanari, U.
Only binary constraints are treated here, but they are represented in full generality as binary relations. Constraints among more than two variables are then represented as networks of simultaneous binary relations. In general, more than one equivalent (i.e., representing the same constraint) network can be found: a minimal equivalent network is shown to exist, and its computation is shown to solve most practical problems about constraint handling. Anyway, constraints are treated algebraically, and the solution of a system of linear equations in this algebra provides an approximation of the minimal network.