Thursday, October 25, 2012

Competing Project Constraints

We have seen earlier that managing a project includes balancing the competing project constraints. As a project manager, we should be clear that projects need to be performed and delivered under certain constraints.

But, what is a constraint? A constraint is anything that limits the boundary of your problem. For example, if I tell you to construct a house in 2400 sq. ft, then I am giving you a constraint. The constraint here is you have to build the house within the given land area of 2400 sq. ft. I would also tell you that I have only $100,000 for the construction of the house. Again, I am limiting your project to a boundary, beyond which you are not allowed to go. I could also tell you that I need the house to be handed over to me within one year. Again, this is a constraint. So, overall, I have given three constraints above:
  1. Land area: Not to exceed 2400 sq.ft
  2. Cost: Not to exceed $100,000
  3. Time: To complete within a year
Triple Constraints: Scope, Time and Cost

Triple Constraints: In project management, three constraints are considered very critical. They are
  1. Schedule/ time,
  2. Budget/ cost and
  3. Scope.
It is not possible to say which of these three constraints are the most important one. The specific project will influence the constraints on which the project manager needs to focus. For example, if we are working on Y2K project, what would be your most important constraint? No doubt, it is time; we need to complete the project before the clock turns to 1st January 2000. Right? How about the construction of a stadium for the Olympic Games? Once again, time might be the driving constraint. How about the construction of your own house? Your most important constraint may be the cost. You don't mind a delay of a month or two. But, you do not want to spend more money than what is originally planned for.

When I say that certain constraint is important, it does not mean that we are neglecting the other constraints. We still need to try to work within those constraints. But, as a project manager, you know where the priority lies. That is more important.

Competing Project Constraints: PMBOK extends the triple constraints and calls the following as competing project cosntraints:

Competing Project Constraints: Scope, Time, Cost, Quality, Resources and Risk
  1. Schedule/ time
  2. Budget/ cost
  3. Scope
  4. Quality
  5. Resources and
  6. Risk

Impact of change in constraints: If any one constraint changes, at least one other constraint is likely to be affected. For example, to shorten the schedule, you need additional resources which may lead to an increase in the cost. So, it is important for the project management team to evaluate the effect of change in one constraint on other constraints.

Importance of Constraints for Project Planning: While it may seem that constraints are difficult to handle, it is very much necessary to define a finite problem. If there are no constraints, you would be working with an indefinite problem in space. So, its always important for a project manager to understand and list down the constraints in a project. This would help him/ her to effectively plan the project. During planning, the project management team should be clear that they are able to work within all the given constraints. If it is found that the constraints cannot be met, then it has to be brought to the notice of the senior management (or) project sponsor (or) the customer.


  1. Competing Project Constraints star is nonsense. It is always the scope, cost and time. Resource and risk can only be subgroups of cost and time. Resources mean cost and time. Risks can cost and delay the project.

    1. I too agree with you. Yes, all the constraints would generally fit within scope, cost and time. But, this is how PMBOK would like to explicitly state the extended set of constraints.

      Thanks for your comments and opinion.

    2. Realistically, you can have resource constraints that can't be solved by money within the time available (you literally can't find and hire an appropriate person in the time available). Also, because the quality aspect of scope is often overlooked (and scope is taken to mean just features) you can deliver a project that looks good on the time, cost, and scope (features) side but suffers from poor quality. You can also be in a situation that is high risk (because of outside factors, for example) where you may indeed complete it with time, cost, and scope intact ... but there's a 30% chance that, for example, a key person will quit, some technology will change, or a law will change which would scupper your whole project plan. So it's correct to identify 6 factors instead of 3.

    3. Yes Andrew, your points are valid.

      But, the three constraints were easier to manage. I always felt Scope, Time and Cost are the core areas. Most of the risks would fit within Scope risk, Cost risk and Time risk. Similarly, quality hinges a lot on scope definition. The product acceptance criteria is part of scope.

      However, I am not against making it obvious by increasing the constraints to six.

  2. To update the star model with the six competing restraints, at the center of the star is a seventh constraint - "Customer Satisfaction"