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Triple Constraint
By Raymond Keckler | August 30, 2007
Projects have always been defined “successful” if they were on time and within budget. However, there are other requirements that define success in a project. Were the goals defined in the project met as stated in the scope? Was the customer satisfied with the end product? Was the proper team and relationships used in the project? These questions leverage project scope, time and cost to produce a product or service that has what the customer wants. These three constraints are what project managers call the triple constraint.
The triple constraint uses project scope, time and cost. Project quality is affected by these three factors. Along with quality, resources are also affected. The triple constraint is considered a triangle. The three constraints make up the triangle and the area inside the triangle are quality and resources. As one side is elongated or shortened, the other two sides have to change and the area inside gets smaller or larger.
Project Scope is defined as the work that must be performed to deliver a product, service or result with the specified features and functions (PMBOK Guide). This is the actual work that resources do to achieve the goals of the project. As the scope line in increased in the triangle, either or both time and cost need to change. Cost will change due to more resources need for the project. Time will change due to the amount of work that needs to be done. If the time cannot change, cost will change due to the increased resources needed to still be on time. Scope creep will kill a project sooner than anything else. It is important to manage scope carefully. There must be a deadline for new changes that can be made for a project. After that deadline is reached, there should be no more changes to the project. This should be defined in the Project Scope Management Plan. This document describes how the project scope will be defined, developed, and verified and how the work breakdown structure will be created and defined, and that provides guidance on how the project scope will be managed and controlled by the project management team. It is contained in or is a subsidiary plan of the project management plan. The project scope management plan can be informal and broadly framed, or formal and highly detailed, based on the needs of the project (PMBOK Guide).
Time can be hard to manage. A lot of things can happen in a project. The stakeholders have influence on time. The stakeholders influence is highest at the start of the project and progressively lowers as the time proceeds in the project. This is due to the changes in cost rise the stakeholders influence diminishes. So as we near the end of the project, cost can go up. If more items are needed in the project but the time cannot change, more resources must be added or quality degrades rapidly. More resources mean more cost. If the stakeholders do not want to put more money into the project, their influence on what can go into the project is reduced.
To be within budget and on time means to control project scope, time and cost. Controlling these three constraints allows you to control quality and resources. It is important to document the project through the Project Scope Management Plan. This will give definitive answers about the project and setup goals. Managing the triple constraint properly can help ensure a successful project completion.
A Guide to the Project Management Body of Knowledge, Third Edition, PMBOK Guide. Project Management Institute, Inc. Pennsylvania, 2004.
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