Projections of Logic Programs Using Symbol Mappings

This work presents some formalization of our intuition that from an operational perspective, logic programs do have a notion of control flow, and the computational behavior of a “well-structured” logic program is best understood in terms of the central control flow the program embodies. Generalizing earlier work on program map theory, a concept of a projection of a logic program using a mapping for the literals appearing in the program clauses is introduced. If a well-structured program is considered an annotation of a basic control flow then projecting out the annotations will abstract the core structure. Projections are particularly useful for incremental program development methods. We demonstrate, using an incremental method for program construction from reusable components, that incremental addition of functionalities can be analyzed for a better design by manipulating the projection equations. We study the relationship between a program and its projections and characterize situations under which the functionality of a program can be orthogonally decomposed so that subsets of functionalities can be independently developed and understood. An example analysis for a better design using projections is presented.