extProlog as Logic Programming Language

Abstract

This chapter presents the theoretical base of extProlog. It is discussed as a logic programming language. It would therefore be convenient to start with the definition of logic programming; however, there is no formal definition of a logic programming language. It is commonly understood that a logic programming language is one that has the ultimate goal of providing clarity and declarativeness for programming. In general, a programming activity consists of two parts: design of the algorithm (heuristic) and its implementation in a language. The algorithm part can be further decomposed into a logic aspect and a control aspect. The logic aspect refers to the facts or data and the rules and requirements specifying what the algorithm does. The control aspect refers to how the algorithm can be implemented by arranging the rules and requirements in a particular order. The latter aspect becomes serious when the algorithm is modified.