Evolutionary migration of legacy systems to an object-based distributed environment

There is an increasing interest in migrating legacy systems to new hardware platforms and to new software development paradigms. High maintenance costs and lack of documentation are among the challenges facing software engineers who wish to migrate such systems. The increasing emphasis on distributed systems and on the object-oriented paradigm suggests that object-oriented, component-based, distributed systems will represent a significant portion of the next generation of software systems. We present a semiautomatic, evolutionary migration methodology for legacy systems which produces an object-based distributed system. We use ISA which is a design recovery and subsystem classification technique that produces a data-cohesive hierarchical subsystem decomposition of the subject system. We adapt the subsystems to the object-oriented paradigm. We wrap and define interfaces of the subsystems in order to define components. Components are allocated to multiple sites. Finally, middleware technologies for distributed systems are used to implement the communication between components. The approach is suitable for the evolutionary migration of legacy systems since each component can be reengineered separately.