An important goal for designers is a consistent user interface. However, the definition of consistency is elusive and has multiple levels that are sometimes in
conflict; it is also sometimes advantageous to be inconsistent. The argument for
consistency is that a command language or set of actions should be orderly, pre-
dictable, describable by a few rules, and therefore easy to learn and retain. These
overlapping concepts are conveyed by an example that shows two kinds of
inconsistency (Aillustrates lack of any attempt at consistency, and B shows consistency except for a single violation):