1.5. Four Project Constraints
Before we move on, let's look at the four project constraints. Don't confuse this with task constraints, which is a separate matter altogether. The project constraints are scope, time, cost, and quality (quality is sometimes referred to a functionality, performance, or features). They're often written as a formula to denote the relationship between the elements. You typically can't take these four elements and perform a mathematical calculation on them based on the formula, but it does describe the relationship between these elements:
Let's define each term here.
The relationship describes how these elements are related because if you increase the scope, either intentionally or via the insidious scope creep, you will have to modify at least one of the three elements on the other side of the equal sign. For instance, if you want to increase scope, you will either have to spend more time or more money (or both) to accomplish the additional work. Alternately, if you increase scope and you cannot increase the time or cost, you will most likely have to reduce the quality. If a project is set to go and you're suddenly told you must do the project for 30% less money or in 20% less time, something has to change. The relationship among these elements is important to understand and we'll spend time working on this concept and give you specific tools to use.
Here's a corollary to that conceptyou cannot initially define all four variables. If you were to randomly select four numbers10, 2, 4, 9and plug them into this equation, it won't work. You need to have one or more variables to make the equation work with the other randomly selected numbers. In this case, we'll use 10, 2, 4 and y. Now, if you try to make the equation work, you solve for y and you can always solve the equation, regardless of what those three numbers are. The same holds true for the relationship between scope, time, cost, and quality. You can't define all four at the front end of the project and expect that the project will succeed (achieve all four metrics). There is a very high likelihood that it won't.
Often when you're handed a project, you're told what to accomplish (scope), how quickly you must complete it (time), what the budget will be (cost) and what features the project must include (quality). That's the best recipe for project disaster ever devised and yet it's done every day in companies all over the world. It's important to note that we're talking about projects that are just dropped in your lap with these four parameters defined for you without any research or planning behind the numbers. If the project has been thought through and experienced subject matter experts have worked to develop these four parameters, it is possible you might hit these numbers. As the project manager, your job is to do the planning that will allow you to more accurately define all four elements. Once those are defined and the project begins, those are the metrics you're going to try to meet. Once you've planned your project, it is not only possible to define all four elements, it's expected. Later in this book, we'll look at these elements and how to negotiate so that at least one becomes your "variable" so you actually can solve your project equation and how to develop these four variables when you're in the planning phase of your project.