Modularity for logical knowledge bases

The author argues that modularity is essential for the design, verification, and maintenance of large-scale knowledge based systems. Motivated by work on software modules and algebraic specification, he introduces a module concept with formal interfaces, and gives semantics and correctness notions for such modules based on logic programming. Single modules communicate with their environment by their interfaces. He discusses how modular systems can be built from single modules by means of so-called module operations, and derive for the composition operation results concerning compositionality of semantics and correctness preservation