Project triple constraints are time, cost, and quality. These are the three constraints that control the performance of the project. Think about this triple-constraint as a three-leg tripod. If one of the legs is elongated or shortened, the other two legs should do something to compensate for that. If we say that the objective of the project is to produce a cheap product, then we need to compromise between time and quality. If the product should be cheap and released in a short period of time, then you know how good the quality of the product will be.
The triple-constraint is logical constraints that we face in everyday life. For example when shopping for a computer with the highest quality, we may find it in a store next door and go to pick it up in few minutes at a higher price. If you scarify the time for a lower price, you may order it online. However, it is most of the time hard to get the computer both cheap and delivered faster.
It is during project execution. Reducing one constraint, will surely affect at least another one.
Other variations of this triple-constraint triangle are:
These are coming from different understandings of the words based on the background of each of the professionals who suggest different legs. All of them serve the same purpose for different types of projects. If you think that scope is a part of quality based on the original definition of quality that it is how close we are to the agreed upon specifications, then we go with quality because it covers scope and more. Others think of the scope as the constituent of time, cost, and quality. Schedules include the effects of time and cost. Risk could be included in the cost from an early stage.
Resources (labor and non-labor) are translated directly into cost. The topic of triple constraints will be examined again when we come to the discussion of project manager skills and how he/she should educate the client about the triple constraints to keep them informed about the impacts of their requirements.