Extracting contracts for the safe reengineering of legacy software

Work on reengineering existing software has largely consisted of parsing existing code (machine of assembly), reconstructing the control flow and data flow, and providing hopefully equivalent behavior in a modern language. We propose a development complementing current approaches by focusing on the high-level picture: the *contracts* behind software elements, expressing their specifications, according to the widely influential methodology of Design by Contract developed by our company. The approach, applied to legacy software units, will yield:  Key abstractions of the software, leading to a modular structure conforming to modern views of modularity, in particular data abstraction and object technology.  For each software element, contracts expressing the purpose behind the implementation. Such a form of reengineering is intended to yield a form of the software that has strong modularity and precise specifications, and so is ready for further evolution and reuse, on a par with more recently written program elements benefitting from the full power of modern programming techniques.