ch9: software evolution

evolution and servicing stages

Organizations must maintain value of software by changing and updating it.

software evolution

An iterative stage in a software system’s life cycle where it is in
operational use and is evolving as new requirements are
proposed and implemented in the system.

software servicing

At this stage, the software remains useful but the only changes
made are those required to keep it operational, i.e. bug fixes and
changes to reflect changes in the software’s environment. No
new functionality is added.

software retirement

The software may still be used but no further changes are made
to it.

change identification and evolution processes

change implementation

Iteration of the development process where the revisions
to the system are designed, implemented and tested.

urgent change requests

Change requests that may have to be implemented without
going through all stages of the software engineering process.

software maintenance

Modifying a program after it has been put into use. Three types:

1. Bug fixing

2. Modifying for new environment

3. Implementing new/changed requirements

types of maintenance

a) fault repairs
b) environmental adaptation
c) functionality addition and modification

maintenance effort distribution

maintenance costs

Costs of preserving software, which is usually greater than development cost.

software reengineering

Restructuring or rewriting part or all of a legacy system
without changing its functionality, after a system has been maintained for some time.

advantages of reengineering

• reduced risk

• reduced cost

reengineering process activities

1. source code translation

2. reverse engineering

3. program structure improvement

4. program modularization

5. data reengineering

reengineering cost factors

• software quality

• tool support

• extent of data conversion required

• availability of expert staff

refactoring

‘Preventative maintenance’; Process of continuously making improvements to a program to slow down degradation through change.

bad smells

• duplicate code

• long methods

• switch statements

• data clumping

• speculative generality