Software Evolution

Software Evolution

why 1

new requirements

why 2

business environment changes

why 3

errors must be repaired

why 4

new hardware may be added to the system

why 5

performance or reliability may have to be improved

evolution

system is in operational use and evolving as new requirements are proposed and implemented

servicing

system remains useful but changes are only made to keep it operational, no new functionality

phase out

system may still be used but no further changes are made

software evolution processes depend on 1

type of software being maintained

software evolution processes depend on 2

development processes used

software evolution processes depend on 3

skills and experience of people involved

handover problem

mismatch between development and evolution approaches

legacy system

older systems that rely on languages and technologies that are no longer used for new systems development

legacy system replacement risk 1

lack of complete system spec

legacy system replacement risk 2

tight integration of system and business

legacy system replacement risk 3

undocumented business rules embedded in legacy system

legacy system expensive to change 1

no consistent programming style

legacy system expensive to change 2

use of obsolete programming languages with few people available with the required skills

legacy system expensive to change 3

system structure degradation

fault repairs

changing a system to fix bugs or vulnerabilities

environmental adaptation

maintenance to adapt software to a different operating environment

functionality addition and modification

modifying the system to satisfy new requirements

software re-engineering

rewriting part or all of an existing system without changing functionality

benefits of re-engineering

reduced risk, reduced cost

refactoring

making improvements to a program to slow down degradation through change