Formal specifications and reliability: an experimental study

An experimental study was undertaken to assess the improvement in program quality by using formal specifications. Specifications in the Z notation were developed for a simple but realistic anti-missile system. These specifications were then used to develop two versions in C by two programmers. Another set of three versions in Ada were independently developed from informal specifications in English. A comparison of the reliability of the resulting programs suggests the advantages of using formal specifications in terms of number of errors detected. Also, several errors that have been known to occur in earlier experiments dealing with this system were avoided by the use of formal specifications