An Incremental Object-Oriented Migration Strategy for RPG Legacy Systems

We present a strategy for incrementally migrating legacy systems to object-oriented platforms. The migration process consists of six sequential phases and encompasses reverse engineering and reengineering activities. The aim of reverse engineering is to decompose programs into components implementing the user interface and components implementing application domain objects. The identification of objects is centred around persistent data stores and exploits object-oriented design metrics. Wrapping is the core of the reengineering activities. It makes new systems able to exploit existing resources, thus allowing an incremental and selective replacement of the identified objects. The migration strategy has been defined and experimented within the project ERCOLE (Encapsulation, Reengineering and Coexistence of Object with Legacy) on legacy systems developed in RPG for the IBM AS/400 environment