Abstraction: a key notation for reverse engineering in a system re-engineering approach.

This paper advocates that extracting formal specification semantically consistent to the original legacy system will facilitate further redesign and forward engineering greatly. The three parts of reengineering could be integrated on the basis of a wide spectrum language. The key approach to comprehension and the production of formal specification is a notion of abstraction. Transformation can help to change the original source code into alternative forms, but with the same semantics. Abstraction is often interpreted as the act of hiding irrelevant details. What constitute as relevant details is often left open to different interpretations. A unified approach for reverse engineering is described within which the notion of abstraction is classified and precisely defined. Abstraction rules are given and applied to various case studie