To capture these notions, Reisner (1981) proposed an action grammar to
describe two versions of a graphics-system interface. She demonstrated that
the version that had a simpler grammar was easier to learn. Payne and Green
(1986) expanded her work by addressing the multiple levels of consistency
(lexical, syntactic, and semantic) through a notational structure they call taskaction grammars (TAGs). They also address some aspects of completeness of a
language by trying to characterize a complete set of tasks; for example, up,