The theorists have won. The latest version of Project Management Institute’s (PMI)® Project Management Body of Knowledge (PMBOK® Guide) has done away with the project triangle, often referred to as the triple constraint. For more than fifty years this simple model allowed people inside and outside the profession of project management to understand the high level dynamics involved in projects.
The project triangle represents the relationships between scope, time, and cost. Scope is the sum of all products and services to be provided. It includes all the work that must be performed to deliver the product or service (tasks and activities) at the negotiated grade (level of quality and amount of redundancy). Time is the duration that is needed to complete all the associated project work (calendar days, months, and years). Cost is the monetary value of the labor expended and all other direct charges that will be incurred during the project (travel, hardware, and software).
When the value of one side is changed, one or both of the other sides are almost always affected. Successfully managing projects requires an understanding of the dynamics of these relationships. When one side of the triangle is an accurate reflection of the demands of the other two sides, the project triangle is said to be harmonized. For example, a project with a scope of building a 5,000 sq. ft. home in two months at a cost of $40,000 is unrealistic; time does not accurately represent the demands of scope and cost. To harmonize the triangular relationship of this project, the cost of the home would have to be increased or its scope decreased, or both.
Boo-yah . . . that’s it. This straight forward concept has allowed numerous project managers, project sponsors, and team members to come together and work through project issues. PMI® has replaced the project triangle with an infinite number of constraints. While the change is not wrong, it provides no practical utility.
PMI® may not recognize the project triangle anymore, but it is still a good thing to have in your tool belt.
*PMBOK is a registered mark of the Project Management Institute, Inc.