Boosting the Quality and Maintainability of Prolog Applications by New Static Analysis Techniques

An approach is presented which supports the development and maintenance of industrial Prolog applications that go beyond prototyping. It is particularly well suited for applications that are considered critical with respect to either reliability or maintainability. The approach is based on an expressive type system combined with a coding standard for Prolog. Properties of predicates like determinism, unfailing, and termination can be specified by the programmer. The notation is completely transparent to the Prolog interpreter and serves as a formalized documentation. Consistency between documentation and code can be checked by automatic static analysis tools integrated in the Prolog Analyzer PAN. Our experience shows that programming productivity and program reliability are improved significantly whereas maintenance costs are reduced by an order of magnitude.