Change Management

Reengineering

Reengineering is the analysis and design of an existing application to bring it into conformance with a methodology. When the application conforms to a methodology, it is rebuilt. To reengineer program code, the code first must be structured. Code restructuring can be done by automated tools. The restructured code from all programs in an application is entered into a CASE tool with reverse engineering capabilities. 

Code restructuring also can be done manually. If no CASE products are used, the code is analyzed and the underlying data and process structures are mapped into a methodology. If Information Engineering is used, for instance, an entity relationship diagram (ERD) and a process data flow diagram (PDFD) are first developed for each program. Then, the diagrams are consolidated across programs to develop application ERDs and PDFDs. A data dictionary to document diagram contents is developed. The ERD is normalized and compared to the automated data to determine the extent of deviation from the normalized state. If the denormalized state was for performance purposes (this is an example of the importance of a historical file of design decisions), then problems with data integrity resulting from the denormalization should be noted for correction. Finally, the detailed process diagrams are used to develop a process hierarchy diagram. The hierarchy diagram is matched to the real organizational functions to determine the extent of application function redesign required.

If the methodology is object-oriented, the code modules are classified by object type and function. If multiple objects call a function, it is classified as reusable and set aside for further analysis. After module classification, the extent to which the code matches a true object design is determined. Reusable modules are evaluated to ensure that they perform single functions, hide information, and use minimal coupling techniques. For minor deviation from the object method, individual modules or object types are reengineered to bring them into conformance with object tenets. For major deviation, the application is reengineered and redeveloped using object techniques.