Any relational language or functional language. These kinds of programming language describe relationships between variables in terms of functions or {inference rules}, and the language executor ({interpreter} or compiler) applies some fixed algorithm to these relations to produce a result. Declarative languages contrast with imperative languages which specify explicit manipulation of the computer' s internal state or procedural languages which specify an explicit sequence of steps to follow. The most common examples of declarative languages are {logic programming} languages such as {Prolog} and {functional languages} like {Haskell}. See also production system. (2004-05-17)
