Software diversity metrics and measurements

The authors define and formalize the concept of software diversity which characterizes N-Version software (NVS) from four different points of view that are designated as structural diversity, fault diversity, tough-spot diversity, and failure diversity. The goals are to find a way to quantify software diversity and to investigate the measurements which can be applied during the life cycle of NVS to gain confidence that operation will be dependable when NVS is actually used. The versions from a six-language N-Version programming project for fault-tolerant flight control software were used in the software diversity measurement.