Formal specifications in software maintenance: from code to Z super(++) and back again

The paper presents a number of techniques that have been developed as components of the software maintenance process as part of the ESPRIT REDO project. These techniques are all based on formal methods, and the work described has provided the mathematical underpinning to a large collaborative project that has been investigating various aspects of software maintenance. The focus of the project has been on reverse engineering, and methods for this part of the maintenance process are reported on here, along with techniques for subsequent re-engineering. A proposal for specification-oriented software maintenance is presented, in which specifications in an object-oriented extension of the formal notation Z are maintained in step with the corresponding programs.