
7.3 Detailed Design 195
While you are using the system, the usage profile may change or some per-
formance bottlenecks may become apparent. In many cases, performance
can be improved by altering the data type of some attribute or, more com-
monly, by adding or deleting an index, without affecting the programs that
access the database in any way. Of course, if the changes affect the pro-
grams, then you have to do program maintenance.
7.3.3 Object-Oriented Design and UML
Many modern software systems are developed using object-oriented tech-
niques. The requirements are usually expressed mainly with use cases. Also,
preliminary class diagrams may have been ...