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9.3 Software maintenance 249

Original Program Reengineered Original Data
Program Documentation Program

Reverse
Engineering

Source Code Program Data
Translation Modularization Reengineering

Program
Structure
Improvement
Restructured Reengineered
Program Data

2. Reduced cost The cost of reengineering may be significantly less than the cost
Figure 9.11 The
reengineering process of developing new software. Ulrich (1990) quotes an example of a commercial
system for which the reimplementation costs were estimated at $50 million. The
system was successfully reengineered for $12 million. I suspect that, with mod-
ern software technology, the relative cost of reimplementation is probably less
than this but will still considerably exceed the costs of reengineering.

Figure 9.11 is a general model of the reengineering process. The input to the
process is a legacy program and the output is an improved and restructured version
of the same program. The activities in this reengineering process are as follows:

1. Source code translation Using a translation tool, the program is converted from
an old programming language to a more modern version of the same language
or to a different language.
2. Reverse engineering The program is analyzed and information extracted from it.
This helps to document its organization and functionality. Again, this process is
usually completely automated.

3. Program structure improvement The control structure of the program is ana-
lyzed and modified to make it easier to read and understand. This can be par-
tially automated but some manual intervention is usually required.
4. Program modularization Related parts of the program are grouped together and,
where appropriate, redundancy is removed. In some cases, this stage may
involve architectural refactoring (e.g., a system that uses several different data
stores may be refactored to use a single repository). This is a manual process.

5. Data reengineering The data processed by the program is changed to reflect
program changes. This may mean redefining database schemas and converting
existing databases to the new structure. You should usually also clean up the