reengineering
Reengineering, also known as both renovation and reclamation, is the examination and alteration of a subject system to reconstitute it in a new form and the subsequent implementation of the new form. Reengineering generally includes some form of reverse engineering (to achieve a more abstract description) followed by some form of forward engineering or restructuring. This may include modifications with respect to new requirements not met by the original system. [Chikofsky&Cross 1990]
A system-changing activity that results in creating a new system that either retains or does not retain the individuality of the initial system. [IEEE 1998]