2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/33288We provide here a simple, yet very general framework that allows us to explain several constraint propagation algorithms in a systematic way. In particular, using the notions commutativity and semi-commutativity, we show how the well-known AC-3, PC-2, DAC and DPC algorithms are instances of a single generic algorithm. The work reported here extends and simplifies that of Apt, cs.AI/9811024.23 pages. To appear in the Proc. 5th International Conference on Principles and Practice of Constraint Programming as an invited talkArtificial IntelligenceProgramming LanguagesD.3.3; I.1.2; I.2.2text