Most methodologies (e.g., requirements, design, etc.) specify functionality in increasing levels of detail.  This is illustrated in Figure 2.  The highest level is generally a major user requirement (e.g., perform file functions, perform edit functions).  Once identified, high level requirements can be broken down into the next -- "intermediate" -- level of user requirements (e.g., reports or screens/windows).  This level, and succeeding levels, can be further decomposed.  Decomposition stops (usually after 3-4 levels) when the requirement is precisely defined -- i.e., there is no ambiguity in the specification of the requirement.

VISIO 5 Drawing

Requirements Decomposition
Figure 2