Structural Validation of Expert Systems Using a Formal Model
Alun D. Preece, Clifford Grossner, P. G. Chander, T. Radhakrishnan · 1993
There are two complementary aspects to testing a software system: functional testing determines how well the system performs its required op-erations; structural testing determines that the components of the system are sufficiently exer-cised during testing. Functional testing is based upon a specification of the system requirements; structural testing is based upon a model of the structure of the system. For rule-based systems, a structural model explicates the rule execution paths (possible causal sequences of rule firings). In this paper, a formal structural model for OPS5-like rule bases is developed; this model is de-signed to overcome weaknesses of previous struc-tural models. Two software tools are introduced: Path Hunter uses the structural model to deter-mine the execution paths in a rule base; Path Tracer analyzes dynamic rule firings that occur during functional testing, to determine the extent to which execution paths identified by the struc-tural model are exercised at run-time. We present results obtained from using Path Hunter and Path Tracer on a complex expert system rule base which had previously been subjected to functional test-ing.