5th Edition PMBOK® Guide—Chapter 2: Project Life Cycle Types (Predictive, Iterative, Agile)


1. Introduction

The first post on this topic two days ago introduced the general topic of project life cycles, which are used to gain better control over a large project and a clearer focus on the deliverables required to complete it. This is done through the splitting up of the project into several phases, each of which can be considered a sort of mini-project in itself which involve all five process groups. The handoff or transfer from one phase to another is done at a stage or phase
gate, sometimes referred to as a milestone or even a kill point. As the last term implies, a project may be terminated if at the end of a phase it is decided that the objectives of the project as a whole will not be able to be completed within the authorized budget and schedule.

The last post done yesterday went into detail about the relationship between the with the usual pattern having them be sequential, but an overlapping or even a parallel relationship is possible. These latter two compress the amount of time taken to complete the project, but do so with the tradeoff of increasing risk of possible rework.

Today’s post will deal with how one plans a project with a life cycle, and there are three types of project life cycles:

  • Predictive (also known as fully plan-driven)
  • Iterative and Incremental
  • Adaptive (also known as change-driven or agile)

2. Predictive Life Cycle (also known as fully plan-driven)

In a predictive life cycle, the three major constraints of the project, the scope, time and cost, are determined ahead of time not just at a high level, but in detail, and the project is split up into phases which can be either sequential or overlapping. Now the planning can be done for the entire project at a detailed level from the beginning of the project, or one can do what is referred to as rolling wave planning (also known as progressive elaboration). This is where the high-level planning is done for the entire project, but the detailed planning is done only for the work that needs to be done in the near future. Then as that work is completed, more detailed planning is done for the work that needs to be completed after that. Do not confuse scope with planning! In a predictive life cycle, the detailed scope of the project is done right from the start; it is only the planning that may not all be worked out detail from the beginning.

3. Iterative and Incremental

Like a predictive life cycle, the project is split up into phases which can be either sequential or overlapping. Unlike the predictive life cycle however, the scope is not determined ahead of time at a detailed level, but only for the first iteration or phase of the project. Once that phase is completed, the detailed scope of the next phase is worked out, and so on.

4. Adaptive (also known as change-driven or agile)

Like an predictive life cycle, the project is split up into phases or iterations which can be sequential or overlapping. However, because adaptive life cycles are used in applications areas such as IT where there is a rapid change, sometimes the processes within the iterations can even be going on in parallel.

Like the iterative and incremental life cycle, the detailed scope is only determined ahead of a time for the current iteration or phase of the project. The phases or iterations are more rapid than in the iterative and incremental life cycle, however, usually with a duration of 2 or 4 weeks. During the iteration, the scope is decomposed into a set of requirements (deliverables) and the work to be done to meet those requirements (often called the product backlog) is prioritized. At the end of the iteration, the work on the product is reviewed by the customer, and the feedback from the customer is used to set the detailed scope of the next iteration.

5. Summary

Here’s a handy table summarizing the differences between the three types of life cycles.

Topic Predictive Iterative Adaptive (agile)
Phases Sequential, overlapping Sequential, overlapping Sequential, overlapping, parallel
High-Level Scope Yes Yes Yes
Detailed Scope At beginning of project Only for each phase Only for each phase or iteration
High-Level Planning Yes Yes Yes
Detailed Planning At beginning of project OR rolling wave Only for each phase Only for each phase or iteration
When Used Product is well understood Large and complex projects Product is not well understood, rapidly changing environments
Customer involvement Beginning, when scope changes, and project end Periodic Continuous

Adaptive or agile life cycles are used now in the majority of IT projects, and PMI has acknowledged its importance by including it in the 5th Edition PMBOK® Guide. In fact, those practitioners of agile methodology now have a separate certification above and beyond the PMP certification, called the PMI-ACP, where the ACP stands for Agile Certified Practitioner.

This concludes the series of posts on chapter 2, and after the weekend, I will start on February 4th a post related to chapter 3, covering project management processes.

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2 Responses

  1. Thanks for the marvelous posting! I definitely enjoyed reading it, you can be a great author.I will always bookmark your blog and definitely will come back someday. I want to encourage you to ultimately continue your great job, have a nice holiday weekend!

  2. Thank you for explaining the differences

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