Merits:
1. Easy to use and
understand.
2. Model is consistent and documentation is provided at each
phase.
3. Suited for small systems where requirements are known
well in advance.
4. Easy to manage as each phase is well defined.
Demerits:
1. Not use full for large projects.
2. Difficult to response to changing customer requirements.
3. Very difficult to go back from each stage.
4. It is difficult to define all requirements at the beginning
of the project.
