What is a Constraint?
A “constraint” is something that limits a person, or an organization, in achieving a goal. As we are accustomed to think that anything that limits our ability must be negative, we automatically think that constraints are negative.
In reality, constraints are a part of nature and part of our every day life. We encounter them in our personal and working experience and we have to learn to manage them.
A constraint may be physical, i.e. linked to capacity, or non-physical, i.e. linked to policy and/or behaviours.
The simplest metaphor to describe a constraint is a chain of links. Let’s imagine a chain made of ten links, nine of which can each bear a weight of above five kilos, while the tenth link can only bear three kilos. Therefore, the weight that the chain as a ‘system of links’ can actually bear is limited to three kilos, and this is determined by the weakest link, its “constraint”. This is an example of what we call a physical constraint.
This concept can be applied to any kind of system (organization). A system (organization) is made up of different and interdependent individuals and activities (structure and “set of conversations”). It is limited in its ability to achieve its goal by the mental models (assumptions) that characterize the system, and these are determined by the environment, the dominant culture, and the personal convictions of the individuals. These kinds of constraints limit the capacity of the system to generate new ideas and/or, in general, to find solutions to problems.
The constraint, therefore, is the factor that determines the speed with which the system can generate new ideas/solutions, or the speed with which it can produce and sell new products. In general, in the case off for-profit organizations, it determines the speed of generation of Throughput and, therefore, the growth of the organization.
The most common method of dealing with constraints is to try and eliminate them, because of their negative connotation. In the case of physical constraints, people try to substitute or eliminate the “weak link”, whereas in the case of non-physical constraints it may be the “boss” who decides what to do about them.
The IM approach to the Theory of Constraints
The IM approach, instead, is to realize that constraints exist and they need to be managed. Any attempt at improvement, whether it be for individual goals or system goals, must pivot around focussing on one single point, the constraint.
It is easier to manage a constrained system because our attention does not have to be spread over all elements of the system, be they individuals and their interrelations, machines and/or activities with their interdependencies or, in the case of thinking processes, the multitude of biochemical micro reactions linked to cognition. We only have to focus on the constraint, as it is the constraint that determines the final result.
The methodology that IM uses to manage any kind of problem is the DecalogueTM.
The practical applications for managing the various kinds of constraints are different from a technical perspective, but the logical process underpinning them is always the same.
This process is made up of three phases:
- Identify the constraint
- Exploit the constraint
- Subordinate to the constraint
Traditionally, the TOC approach explains that if you break the constraint, it will shift elsewhere and the three phases need to be repeated. The IM approach, instead, prefers to choose the constraint strategically, and design the system around that strategic constraint for as long as is possible, creating a stable system with statistical methods to manage variation, thus minimizing the disruption and cost of a constantly shifting constraint.
These three phases are completely general, and they are used both for physical constraints, such as a machine or a production phase for manufacturing, and for non-physical constraints such as those linked to organization policies, or, in general, the cognitive constraints of individuals. Examples of practical applications are Drum Buffer Rope (DBR) for production, Critical Chain for project management, and the Thinking Process Tools, a simple and yet sophisticated set of tools for thinking developed by Eliyahu Goldratt to manage non-physical constraints.