6th Edition PMBOK® Guide–Project Life Cycles

I am starting a project of going through the 6th Edition of the PMBOK® Guide and blogging about its contents.    The 6th Edition was released on September 22nd by the Project Management Institute, and the first chapter is a general introduction to the framework in which project management exists, starting with section 1.2 Foundation Elements (section 1.1 describes the purpose of the Guide).

The section I am going over in this blog post is section 1.2.4 Components of the Guide, although it should be titled Components of a Project (in my humble opinion).    The reason is that the preceding section, 1.2.3 Relationship of Project, Program, Portfolio, and Operations Management shows the external relationship between a project and all of these other elements within an organization.   The current section 1.2.4 now shifts from an external view of a project to an internal one, and shows what its components are.  Here they are in decreasing order of magnitude:   project life cycle, project phase, process group/knowledge area, process.   In this first post, I will discuss the largest component, the project life cycle.

The project life cycle is a series of phases that a project passes through from its start to its completion.    There are several types of project life cycles, from predictive, to iterative/incremental, and adaptive (agile).    They vary in terms of how the project constraints of scope, time and cost evolve during the life cycle, from the most rigid (predictive) to the most fluid (agile).

Predictive–project scope, time and cost are determined in the early phases of the life cycle.   This is also known as a “waterfall” life cycle.

Iterative–the project scope is determined in the early phases of the life cycle, but the time and cost estimates are modified as the team’s understanding of the project increases.

Incremental–the project scope is produced through a series of iterations that successively add functionality of the product.    The “spiral” model of project management is an example of this type of project life cycle.

NOTE:    Anthony Mersino, in his VitalityChicago blog, says that although PMI describes these last two project life cycles, iterative and incremental as being separate, they are often done together, so that the scope as well as the time/cost estimates are modified in a series of iterations.

Adaptive–here it is often the time and cost constraints which are determined in the early phases of the life cycle; it is the scope that continuously evolves based on interactions with the customer.

Here is a comparison of how requirements, deliverables, change, stakeholders, and risk/cost are handled in the various types of project life cycles.    (Taken from Figure X3-1. The Continuum of Project Life Cycles on page 666 of the Guide.

  Predictive Iterative



Requirements Defined up-front Elaborated periodically  

Elaborated frequently

Deliverables Delivered at end of project Delivered periodically Delivered frequently
Change Constrained as much as possible Incorporated at periodic intervals Incorporated in real-time delivery
Stakeholders Involved at specific milestones Involved regularly Involved continuously
Risk/cost Controlled by detailed planning Controlled by progressively elaborating Controlled as requirements emerge

There is an additional type called hybrid which combines the predictive and adaptive life cycles.   The elements that are well known or have fixed requirements follow a predictive life cycle, and those that are still evolving follow an adaptive life cycle.

Although this is often hyped as the trend in which project management is going, there are many caveats to using the hybrid approach, some of which are touched upon by Anthony Mersino in his blog about agile project management called VitalityChicago.   So mix and match project life cycles at your own risk!


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