A framework for the credit-apportionment process in rule-based systems

A framework for the credit-apportionment process is described. Such a framework is vital in studying the credit-apportionment problem because it provides a formal basis for the problem analysis and algorithm design. The framework includes: a system-environment model, which integrates the effects of payoffs with other relevant parts of a rule-based system to model various internal and external activities of the rule-based system; and principles of usefulness, which define the inherent usefulness of rule actions and provide the semantic aspect of the credit-apportionment process. This framework formulates the credit-apportionment problem as a problem of estimating and approximating the inherent usefulness from payoffs. Two conclusions from the framework are that: the usefulness of rule action is a function of the context in which the rule activates; and the scalar-valued rule strength is not adequate for the purpose of a credit-apportionment. These conclusions led to the development of a credit-apportionment algorithm, the context-array bucket-brigade algorithm