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Identify Project Drivers, Constraints, and Degrees of Freedom (#3 in the series 21 Project Management Success Tips)
By Karl E. Wiegers

Every project must balance its functionality, staffing, cost, schedule, and quality objectives [Wiegers, 1996]. Define each of these five project dimensions as either a constraint within which you must operate, a driver strongly aligned with project success, or a degree of freedom you can adjust within some stated bounds. There’s bad news: not all factors can be constraints and not all can be drivers. The project manager must have some flexibility to react to schedule slips, demands for increased functionality, staff turnover, and other realities.

A “flexibility diagram” such as that shown in Figure 1 visually depicts your constraints, drivers, and degrees of freedom. A constraint gives the project manager no flexibility in that dimension, so it is plotted at the zero value on its axis. A driver yields a small amount of flexibility, so its point is plotted a bit higher than zero. Degrees of freedom provide varying degrees of latitude. They represent parameters the project manager can adjust to achieve the project’s success drivers within the limits imposed by its constraints. Connecting the five plotted points creates an irregular pentagon. The smaller the area inside the pentagon, the more constrained the project is.

Flexibility Diagram

Figure 1. A flexibility diagram for a project that is staff-constrained and schedule-constrained, with cost being a driver, and quality and features being degrees of freedom.

I once heard a senior manager ask a project leader how long it would take to deliver a planned new large software system. The project leader replied, “Two years.” The senior manager said, “No, that’s too long. I need it in six months.” The project leader’s response was simply, “Okay,” despite the fact that nothing had changed in the few seconds of that conversation to make the six-month target achievable. A better response would have been to negotiate a realistic outcome through a series of questions such as the following:

  • How critical is the six-month target? Does something drastic happen if we don’t deliver in six months [schedule is a constraint], or is that just a desirable target date [schedule is a driver]?
  • If the six months is a firm limit, what subset of the requested functionality do you absolutely need delivered by then?
  • Can I get more people to work on it? [staff is a degree of freedom]
  • Do you care how well it works? [quality is a degree of freedom]

Adapted from “Practical Project Initiation: A Handbook with Tools” (Microsoft Press, 2007). A condensed version of this paper was published in Software Development magazine.

Karl Wiegers, Ph.D., is Principal Consultant with Process Impact, a software process consulting and education company in Portland, Oregon. Karl’s most recent book is “Practical Project Initiation: A Handbook with Tools.” Karl is also the author of four other books and 170 articles. Karl is a frequent speaker at software conferences and professional society meetings. You can reach Karl through or

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