Application of Formal Speci cation to Software Maintenance

This paper describes the use of formal speci cations and associated tools in addressing various aspects of software maintenance | corrective, perfective, and adaptive. It also addresses the re nement of the software development process to build programs that are easily maintainable. The task of software maintenance in our case includes the task of maintaining the speci cation as well as maintaining the program. We focus on the use of Anna, a speci cation language for formally specifying Ada programs, to aid us in maintaining Ada programs. These techniques are applicable to most other speci cation language and programming language environments. The tools of interest are: (1) the Anna Speci cation Analyzerwhich allows us to analyze the speci cation for correctness with respect to our informal understanding of program behavior; and (2) the Anna Consistency Checking System which monitors the Ada program at runtime based on the Anna speci cation.