A novel method for extracting knowledge from neural networks with evolving SQL queries

While artificial neural networks (ANNs) are undoubtedly powerful classifiers their results are sometimes treated with suspicion. This is because their decisions are not open to inspection - the knowledge they contain is hidden. In this paper we describe a method for extracting and representing the knowledge within an ANN. Mappings between inputs and output classifications are stored in a table and, for each classification, Structured Query Language (SQL) queries are evolved using a genetic algorithm. Each evolved query is a simple, human-readable representation of the knowledge used by the ANN to decide on the classification based on the inputs. This method can also be used to show how the knowledge within an ANN develops as it is trained, and can help to identify problems that are particularly hard, or easy, for ANNs to classify.