Often the initial step in building an app is that you have some data that you want to analyze, but you don't necessarily know exactly what you want to look for in the data. As a business user, you can—and should—just load this data into Qlik Sense and start developing. Our experience is that the best way to develop the app is to start without first defining the requirements.
The reason is that when you load data and start to create visualizations, you learn from data. This knowledge is very important once you start defining what you want to analyze. Hence, you should first develop a basic app, then take a break and evaluate what you learned. Now is the right time to start formulating the requirements.
Another common case is the opposite situation: you know that you want to calculate a specific KPI, for example, supplier efficiency, but you don't necessarily know what data you need to be able to do this. In this case, you need to start with some research about...