The Command Language Grammar: a representation for the user interface of interactive computer systems

Abstract

This article introduces and discusses a specific grammatical structure—the Command Language Grammar (CLG)—as a representational framework for describing the user interface aspects of interactive computer systems. CLG partitions a system into a Conceptual Component (tasks and abstract concepts), a Communication Component (command language), and a Physical Component (display, keyboard, etc.), The components are further stratified into distinct Levels—a Task Level, a Semantic Level, a Syntactic Level, and an Interaction Level-each Level being a complete description of the system at its level of abstraction. Each Level's description contains procedures for accomplishing the tasks addressed by the system in terms of the actions available at that Level. That is, the system is described by progressive refinement. An extensive example, a small message-processing system, is described at all Levels in the CLG notation. CLG is discussed from three points of view: the Linguistic View sees CLG as elaborating the structure of the system's user interface and of the communication between the user and the system. The principal goal of CLG in this view is to lay out the space of command language systems. The Psychological View sees CLG as describing the user's mental model of the system. The main concern in this view is with the psychological validity of the CLG description. The Design View sees CLG as a series of representations for specifying the design of a system. CLG proposes a top-down design process in which the conceptual model of the system is first specified and then a command language is created to communicate with it.