Going through project management courses, I've become intimately (if not sickeningly) familiar with the so-called "triple constraint" of time (AKA schedule), cost, and performance (AKA quality or scope). The basic idea here is that there is a balance, and a trade-off, between these three factors that is necessary to successfully complete any project. I even remember telling my old clients (back when I was doing some consulting work) that they could choose any two (i.e. time and scope; scope and cost) but their choices would influence the third, which was under my control (i.e. if they wanted to dictate time and scope, then I got to tell them the cost; if they wanted to control cost and scope, they had to work on my schedule). This concept is so ingrained into the project management mentality that I assumed there wasn't much left to discuss about project constraints. So imagine my surprise, fellow thinker, when I learned of a bright, shiny, new (to me at least) fourth constraint - customer acceptance!
Customer acceptance is a constraint that can change the way we view our role as a project manager. It forces us to think outside of technical success and shift to more of an outward focus on customer requirements. In this manner, it also increases the importance of communication and understanding during the conceptualization and planning phases - what good is a project that comes in on-time, on-budget, and meets the design criteria if the customer isn't satisfied?
In a way, this new constraint reminds me of a topic in quality management. Quality is a term that really has two definitions: one is the objective view of how well the product conforms to design standards; however, the more important measure of quality is the subjective measure of how happy the client is with the final product. In projects, the triple constraint is basically the technical criteria. But it's this fourth constraint that adds a subjective perspective and says that a project isn't truly successful unless the client says it is.
The idea of a fourth constraint lends itself to another topic from quality management - Quality Function Deployment. QFD uses the "Voice of Customer" (VOC) to thoroughly and accurately define the requirements of a product. Once identified, those requirements are translated into design requirements, which are then translated into engineering requirements. This flow-down ensures that the "how's" from one level become the "what's" at the next level and sight of the original customer "what's" is never lost.
So the fourth constraint is vitally important to any project team, and serves as a bridge between the technical and the subjective measures of project success. And it's about time that someone has defined this link and clearly articulated the importance of the customer in an existing model. I know that I'm sometimes guilty of focusing too much on the internal aspects of a project. Changing the mindset of a PM to look at all four constraints should have a substantial positive impact on performance.
