Re-implementing a legacy system

Re-implementation is one of the alternatives to migrate a legacy software system next to conversion, wrapping and redevelopment. It is a compromise solution between automated conversion and complete redevelopment. The technical architecture can be revised and the code replaced, but the functional architecture – the use cases remains as it was. The challenge of this approach is to preserve the functionality while changing the technical implementation. This approach is taken when conversion is not feasible and redevelopment is too expensive or too great a risk. It entails more than a 1:1 transformation but less than a total rewrite. The same components remain with different contents. In this paper the case for reimplementation is presented and the process described. The tools required to support the process are identified and their use illustrated. Finally, two industrial case studies are presented, one with a VisualAge/ PL/I-DB2 system and one with a COBOL-IMS application.