Constraints fit hand in glove with declarative host programming languages. Three of the most influential constraint programming languages were embedded in Prolog: PrologIII, CLP(R) and CHIP. Whilst all three system are still developing further, there are many new constraint programming systems emerging including ECLiPSe, Oz, 2LP, and Newton.
From a theoretical point of view the extension of logic programming to Constraint Logic Programming (CLP) has been very fruitful. A good survey is
(Jaffar and Maher, 1994). For example ALPS - a form of logic programming with guards - was an extremely influential language, becoming the forerunner of the Concurrent Constraints paradigm
(Saraswat, 1993). Concurrent constraint programming has in turn provided a very clean model of concurrent and multi-agent computing. Constraints can also be modelled in terms of information systems, which allows us to reason about the behaviour of constraint programs at an abstract level.