Validation of knowledge-based systems

This still relatively young research area' requires a methodology distinct from traditional software verification, validation, and testing (VV&T) technology, for two reasons: the nature of the problems to be solved and the lack of explicit functional structure in KBS.

Abstract

Introduction Knowledge-based systems (KBSs) have become ever more important in the development of large, complex software systems in defense, industry, business, and science. Failures in these systems may gravely endanger human life and property. Validation of KBSs thus greatly concerns software systems developers and implementors. This still relatively young research area' requires a methodology distinct from traditional software verification, validation, and testing (VV&T) technology, for two reasons: the nature of the problems to be solved and the lack of explicit functional structure in KBS. In traditional software systems development the problem to be solved is typically well-understood and the requirements statements for the problem exist and are precise and well-defined. KBSs are typically used when the problem is not well-understood, and thus lacks precise requirements statements. Moreover, traditional software is procedural, with explicit control flow within and between modules. KBS software, in contrast, is mostly declarative and nondeterministic, with little or no explicit control and no explicit functional modules. It lacks the explicit functional structure prerequisite to requirements validation. KBSs overcome the first problem through the so-called incremental development paradigm, also referred to as exploratory programming and rapid prototyping. The system designer translates the imprecise, incomplete, and often incorrect requirements into a partial, incomplete but executable KBS written in an expert system (ES) shell, such as ART, OPS5, or KEE. (See the chapter by W. B. Gevarter elsewhere in this volume.) Based on the output, the KBS is modified (corrected, deleted or extended) until the