Limitations of the Triple Constraints
Though useful, it is rather simplistic for the complex environment in which projects are delivered. To understand the limitations of the triple constraints, let’s take another example. Suppose you have delivered a project on time, within budget, met the agreed scope and met the defined quality requirements. Is that an indication of a successful project? Going by the Iron Triangle, it is!
However, in real projects there are other factors or constraints, such as the results after deployment. The priority of constraints is also a variable that needs to be factored. This variable is sometimes dependent on the industry. For example, in NASA and military development, performance is a critical variable. Cost and schedule are not as important.
It is because of such limitations that project practitioners question the validity of the triple constraints as the de-facto framework to manage and evaluate projects. That’s probably the reason for the PMBOK version 4 to state that managing a project involves managing constraints, such as Scope, Quality, Schedule, Budget, Resources and Risk. It is also the reason for the triple constraints to evolve into the Project Management Diamond and the Project Management Star.