Types of Maintenance
The types of maintenance are minor modifications, restructuring, reengineering, or rebuilding. Minor modifications are changes to existing code and can be any of the project manager classifications discussed above. Restructuring is the redevelopment of a portion of an application with a bridge to the old application. Reengineering is the reverse analysis of an old application to conform to a new methodology, usually Information Engineering or object orientation. Reengineering is also known as reverse engineering. Rebuilding is the retirement and redevelopment of an application.
To select the appropriate type of maintenance, several questions are asked (see Figure 18-12). First, ask if the software works. If the answer is no, you retire the old application. Then you reengineer and rebuild it using a methodology. If the answer
is yes, you continue to the next question: Does the application have a high maintenance cost? If the maintenance cost is low, the answer is no; then do a simple revision. If the answer is yes, immediately restructure the parts that do not work,
and reengineer the entire application as part of on-going work.
FIGURE 18-11 Sample Documentation Change with Old Contents
FIGURE 18-12 Decision Tree for Selecting the Maintenance Type