To do this, arrange what users need under chapter headind that represent the users' top-level goals. This list of goals is itself a scenario: if you step through them, you get an idea of what the whole problem is. Usually, the scenarios are simple sequences, one goal after another, but this is not the only possibility, as we will explain. The overall result is a hierarchy, but this is not necessarily preached by top-down analysis - users may instead volunteer whole scenarios, which you will have to fit together into a structure.