Hierarchy 2 of 3: The Interaction Hierarchy

On any interface with more than a few controls there is normally a hierarchy at work. The state of one control affects the state, behaviour, or even visibility of one or more other elements. This is the Interaction Hierarchy, or Hierarchy of Control.

Appropriate grouping and visuals signal this relationship – allowing people to predict behaviour, and to process the interface in “chunks”, rather than all at once.