A Project Management Method - Graphically

The real life business process entity is shown as an integral part of this workflow method because it requires a certain numbers of cycles to analyse, capture and structure all processes needed for the next phases. Depending on the complexity of the process, each phase might need to provide feedback for verification and/or request consensus and/or new information in order to proceed with the next phase of the workflow.

Waterfall Model
Path 1-3-5 describes a classical waterfall model ... maybe the first approach in managing a software development life cycle (SDLC). The various phases A-B-C-D are carried out sequentially but its progress is shown as flowing downwards as a water fall.
The waterfall approach gives the idea that the next phase will start when the water reaches the bottom of the fall, but it's also a way to quantify work (results) as a function of time (see diagram below).

For optimization purposes, activities within phases should be analyzed using the Project Network Diagram technique and, hence, phases could overlap.

Iterative Approach
An iterative approach is a method for delivering application functionalities in an incremental way, i.e., a single iteration can results in one or more deliverables and each deliverable represents a percentage of work to be performed. The degree of percentage of work should be such as to yield some tangible results. The result of an iteration is then used as input to the next iteration. The next iteration could take place in the same phase or the next phase, depending on its results and on the predesignated methodology policy. This process is repeated recursively until completion of an application (or project) is achieved.

The following example graph is the RUP (Rational Unified Process) from IBM  and it illustrates the iterative approach.
Iteration I1, E1, C1, C2, C3, C4, T1, and T2 are similar to sub-phases and can be tailored to meet the needs of an organization.

N.B. - This post is to be completed.