A design situation is a model of the context to which a design intervention will be applied to bring about beneficial change.
A situation is a description of real-world circumstances pertinent to some question or goal.
The goal of designing is to improve the way things are, so design situations are descriptions of real-world circumstances that include all the necessary information to specify not only the “as-is” state of things, but also the information needed to specify the nature and extent of imbalances.
Another way of thinking about this is: to be meaningful, designing must be grounded in some real-life conditions. The less concrete the conditions for which one designs, the less likely that the design intervention will improve things. So the best design interventions will be those that are firmly rooted in real-life conditions.
Say you're designing a stapler. If you want to design a beneficial stapler, you would need to know quite a bit about the circumstances in which the stapler will be manufactured, sold, used, and disposed of.
The answers to these questions are just some of the situational characteristics that typically apply to products like staplers. A beneficial stapler is one that addresses all the pertinent characteristics non-negatively. So you cannot design a beneficial stapler - and therefore discharge your primary responsibility as a designer - without understanding the situation into which your stapler will be introduced.
To answer these questions, you need to study the environment in which your stapler will be used - before you start designing it. If you answer them well, then it is more likely that your stapler design will be balanced for that environment - which means it will provide the desired benefits.
Situations involve many objects, agents, people, phenomena, and non-linear interactions between all them all. The best modelling techniques for situations are therefore those of systems science: flow diagrams, causal loop diagrams, etc.
It is often very difficult to build these diagrams without investing very significant resources into the task. If doing so is beyond the scope of the design task that has been set for you, more informal, narrative techniques may be sufficient. In these techniques, you just describe in natural language the nature of the environmental elements that constitute a situation.
Whether using the tools of systems science or not, the most significant task in modelling situations is gathering the information needed to create that model. No matter how good your modelling skills are, the resulting model is no better than the information you used to build it.
So the question reduces to: How do we gather good-quality, robust, reliable information about a situation?
Answering this question will require doing research, because it's virtually impossible that you'll have the necessary information at hand.
Typically, doing the research for situation modelling will happen in five stages:
Now, your team can build a model of the situation. This can be just the reference document described above, but it is almost always useful((where “useful” in this case means very likely to lead to a better final design.) to build a few diagrammatic elements - as mentioned at the beginning of this section - because diagrams rule.