In project management, there is what is known as a triple restriction of projects, made up of scope, time, and cost. As we know, the scope is the objective to be achieved; the time, the start and end date of the project; and the cost is the established budget.
These three elements are what make up the so-called triple restriction of projects which is represented as an equilateral triangle, which is also often called an iron triangle. The fact that it is represented with an equilateral triangle is not accidental, since its three sides are equal; therefore, it represents the equilibrium and balance of the three variables that will give success to the project.
❝Project management is like juggling three balls: time, cost, and quality. The program management is like a group of circus performers standing in a circle, each juggling three balls and exchanging them from time to time❞ (G. Reiss)
If the equilateral triangle were to modify its sides to be isosceles or scalene, imagine that, in the case of a project: one of the three variables would be modified in the same way, generating as a result that said the project would lose its balance. If we alter any of the variables, the others will be affected.
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It should be noted that the triple restriction of projects is valid for all types of projects, regardless of their size or nature, and the variables are so closely linked that any change in one of them will affect the others, positively or negatively.
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The design stage is one of the most important stages of the project. However, it is during requirements gathering that we define the scope of the project, that is, its end product. Once the scope has been defined and based on the work plan, the stage of assigning resources to the project begins. So, we can apply the triple project constraint concept.
Next, we explain the general restrictions that you must take into account in each variable of the triple restriction of projects.
Time constraints occur when a project in progress must be completed within a certain period. In this sense, to meet the deadline established for delivery, the working hours of the team assigned to the project can be increased. For this reason, it is intuitive to understand the relationship between cost and implementation time.
The project manager must be able to identify changes, even if they are considered minimal, to establish the impact of these on the deadlines or the budget. The estimation of the terms is a key point for a successful implementation. It is important to plan a real schedule of what you want to do, define what the activities to be carried out will be, sequence them and estimate the duration of each one.
Within the activities linked to deadlines, some tools can help you develop the schedule, such as Gantt charts. Once the scope and schedule of the project are defined, we can estimate the costs
The budget restriction is the limit or total budget that we have to spend on a certain project. It means that this limit cannot be exceeded and that all the expenses that the execution of the project requires must fit within the budget. Any change in the other variables will surely modify the budget.
If the project is delayed within the established period for different reasons, such delay will have important consequences at the budget level. Suppose, as an example, that a well-known film production company invests a large budget in a brand new film within a year and a half from the beginning, between pre-production, shooting, and post-production, until the theatrical release.
But it turns out that right in the middle of filming the project is interrupted by the outbreak of a pandemic that prevents its completion on schedule, and inevitably, production is delayed for several months, after filming resumes.
Consequently, the director and the producers of the film will have to calculate the financial losses due to the delay in production and define a new budget to cover the expenses of what remains to be done, taking into account the extra expenses in protocols to preserve the health of the team involved in the project.
In this way, the time variable has a negative influence on the established budget, forcing the director of the film project to remake the schedule, based on a new objective or the same one but significantly modified. Consequently, the budget will also be affected.
A scope constraint can often be produced through a succession of simple requirements from the client or functional project leader which individually represent a very minimal change on the project variables.
In those cases, the project manager must have the ability to identify that those requirements are outside the scope agreed to in the project charter or contract, and therefore, you can politely refuse to implement them. Otherwise, they will generate a deviation in the deadline or the budget.
In projects that have a clear and detailed scope definition, it is more feasible for the project manager to detect possible changes before they occur and, more importantly, to argue that they were not considered initially. On the contrary, in projects that do not have a clear scope definition, such work will be more difficult to carry out.
For this reason, if you are a project manager or work with one, take some time (in proportion to the size of the project) in the detailed definition of the scope, which will avoid later frustrations, and above all, will reduce the risk of not being able to support a requirement that the client is requesting when it is not within the scope of the project.
Returning to the example of the film project, a scope restriction would be that, due to the pandemic, the production cannot be released in movie theaters because they are disabled, and instead, be released on an online channel, under very different advertising and collection conditions.
In short, to ensure that the three variables that make up the triple restriction of projects remain in balance, it is convenient to carry out routine checks or controls to monitor the progress of the project and thus prevent a change in the variables of time and scope from producing unexpected triggers in the planned budget for the project.