Within the DOT framework, you try to solve a central question. Every request or assignment can in principle be reformulated into a question. This is called the main question.
In order to develop a solution for this central assignment, you need information such as "What are the wishes and needs of the end users?" (Field), "What kind of ICT solutions have already been tried for this problem?" (Library), or "Is this prototype indeed faster than the old application?" (Lab). These are sub-questions.