A methodology for the validation and verification of decision making rules is presented. The methodology addresses the general problem of detecting problematic cases in a set of rules expressed as statements in formal logic. This representation of the decision rules makes the problem general in terms of application domains, and also provides an analytical base for defining errors. The approach is based on viewing a rule base as an organization of information that flows from one process (rule) to another. The key step in the methodology is the transformation of the set of decision rules into an equivalent Petri net. The static and dynamic properties of the resulting Petri net are shown to reveal patterns of structures that correspond to the problematic cases. The techniques presented in this paper are based on theory and are supported by software tools.