computer-domain concepts that represent them (for example, folders, spreadsheets, or databases). The second edition amplified the important distinction
between objects and actions, paralleling the familiar separation between nouns
and verbs. In the third edition, the underlying theory of design was called the
object-action interface (OAl-Iet's pronounce it Oo-AhO model. The OAI model is
descriptive and explanatory, and it can also be prescriptive, in that it provides
valuable guidance for designers of interfaces, online help, and training
processes.