The Waterfall Model, classic life cycle
When work flows from communication through deployment in a reasonably linear fashion.
It may also occur in a limited number of new development efforts, but only when
requirements are well defined and reasonably stable.
The waterfall model, sometimes called the classic life cycle, suggests a systematic,
sequential approach6 to software development that begins with customer specification
of requirements and progresses through planning, modeling, construction, and
deployment, culminating in ongoing support of the completed software.
Problems of Waterfall Model:
1. Real projects rarely follow the sequential flow that the model proposes.
2. difficult for the customer to state all requirements explicitly.
3. customer must have patience.
4. other members of the team to complete dependent tasks.
5. time spent waiting can exceed the time spent on productive work.