There are two important variants of waterfall development. The parallel development methodologies evolved to address the lengthy time frame of waterfall development. As shown in Figure 2-3, instead of doing the design and implementation in
sequence, a general design for the whole system is performed. Then the project is
divided into a series of subprojects that can be designed and implemented in parallel.
Once all subprojects are complete, there is a final integration of the separate pieces,
and the system is delivered.