5th Edition PMBOK ® Guide–Chapter 2: Project Life Cycle (Phase Relationships)

The last post dealt with project life cycles in general. A project life cycle is when you split up a project into different phases, which for all effects and purposes each become a mini-project of their own, with their own cycle of 5 process groups from initiating to closing.

The purpose of this post is to discuss the different ways a project can be split up into phases. There are two basic categories to consider:

1. Single-Phase vs. Multi-Phase

Projects can be either single-phase, if they are relatively simple, or can be broken into several phases, in which case you have a multi-phase project.

Fig. 1 Multi-Phase Project

The points to remember about a multi-phase project are the following:

  • Each phase has a different focus; for example, when creating a new automobile, there is the computer design, the creation and testing of a prototype, and then quality assurance that the vehicle can pass regulatory compliance. Each of these phases has a different focus.
  • Each phase is a mini-project in itself that it contains the five process groups of a project. This assures create control over the process and the delivery of a clear deliverable from one phase to another.
  • The closure of one phase is like the closure of a project. It has to be formally accepted before the organization can go to the next project. This is why process 4.6 is called “Close Project of Phase”. However, if the deliverables of the project are NOT accepted, that project can be terminated at any of these points of transfer between one phase and the next. For that reason, the transfer points can be referred to as a stage gate, milestone, phase gate or review, or a kill point.

2. Sequential, Overlapping and Parallel

Now for the most part, phases are sequential. However, just like with the fast-tracking of activities in a project, phases can be made to overlap as well. Here’s an illustration of the difference. Here’s the usual arrangement of phases in a schematic form.

Fig. 2 Sequential Phases

Time Period




Project Phase

Phase 1

Phase 2

Phase 3

However, if you have to accelerate the project’s final outcome, you may try and overlap some of the phases. For example, you may have some individual modules for a software program developed in Phase 1 and then have them debugged in Phase 2, with final testing done in Phase 3.

You may want the debugging process of some of the modules to begin before they are all complete, in which case Phase 2 would start before Phase 1 is done, as in the example below:

Fig. 3. Overlapping project phases

Time Period




Project Phase

← Phase 1 →



←        Phase 2   →          



←  Phase 3 →

However, one important thing to remember is that overlapping phases like this can increase the risk of having to redo some of the work. This is true within a project itself, one method of schedule compression is called fast-tracking, and it involves overlapping some formerly sequential activities. It can reduce the constraint of the amount of time the project takes, but at the cost of increasing the risk. The same is true with overlapping phases.

The PMBOK® Guide does mention a third possibility, that of parallel project phases, but does not illustrate it. Here’s an schematic diagram below.

Fig. 4. Parallel project phases

Time Period




Project Phase

← Phase 1 →


← Phase 2 →



← Phase 3 →

This means that two or more phases go on simultaneously from beginning to end, and then must both be completed successfully in order for the next phase to begin. As you would expect, this has even a higher risk than the overlapping project phases would.

The next post will cover the different ways in which a multi-phase project is planned, in a predictive life cycle (totally planned beforehand), an iterative and incremental life cycle (partially planned at the beginning, with successive iterations throughout the project), and an adaptive or agile life cycle (partially planned at the beginning, with rapid iterations throughout the project).

One Response

  1. This blog is clear and concise

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