On the User-Requisite Variety of Computer Application Software
E. Burton Swanson · IEEE Transactions on Reliability · 1979
In this model for software maintenance, user demand for enhancements and extensions is an integral component. Such demand is directed toward obtaining the user-requisite variety of the software, which manifests itself by recognizing errors of discrimination and omission during a history of data processing. The concept of variety in data and programs is introduced and developed, and measures are suggested. Behavior of the measures over a history of data processing is investigated. Validation and application of the model is discussed.