Historical Rete networks for debugging rule-based systems

To debug a forward-chaining rule-based program, certain, historical, information is needed. System builders should be able to request such information directly, instead of having to rerun the program one step at a time or search a trace of run details. As a first step in designing an explanation system for answering such questions, a proposal is discussed for storing a forward-chaining program run's 'historical' details in its Rete inference network, used to match rule conditions to working memory, without seriously affecting the network's run-time performance. This proposed modified Rete network is called a historical Rete network. Various algorithms for maintaining this network are discussed, along with how it can be used to analyze what happened during a program run.<>