ROBART 2(ID:7259/rob006)Dialogue contruction languageVersion 2 of ROBART Related languages
References: The paper describes the human interface for two versions of an interactive graphics system intended for use by nonprogrammers. It presents the "action languages" for the two versions, then shows how these user languages can be described in terms of a production rule notation. Particular emphasis is given, in the notation, to actions the user has to learn and remember (i.e., to "cognitive" factors). The paper then presents predictions about human performance based on the formal description, and exploratory results of testing some of the predictions. Since the predictions are based on general properties of the formal description, the technique should also be applicable to other "action languages." Extract: Introduction Introduction In both linguistics and computer science, formal grammars are used to describe languages precisely. In linguistics, a grammar is used to describe the rules for generating sentences in a natural language. These rules are usually assumed to be the ones a native speaker of the language follows implicitly in creating and in understanding sentences. In computer science, a grammar is used to describe a programming language to a translator (e.g., compiler) or a compiler generator. The compiler can then be used to translate statements in the programming language into machine language. Formal grammatical description has not, however, been generally applied in the human factors area, which draws primarily on behavioral science for its methodology. Since human factors methodology rarely includes theoretical description or precise prediction based on formal models, the field is often considered "soft" or even ad hoc (at least, by some practitioners of other disciplines). In this paper we illustrate, by means of a detailed example, how formal description can be used as a tool to aid the design of systems for ease of use. We are specifically concerned with "action languages" for interactive systems -- the sequences of button presses, joystick motions, typing actions, etc. -- performed by a user interacting with a terminal. The intent of the paper is to show that an action language can be formally described and that the formal description can be used to compare alternative designs for simplicity and consistency. We are particularly concerned, in the formal description, with "cognitive" factors-what a user has to learn and remember -- rather than with physical actions themselves. By examining such a formal description rather than waiting for construction of a real, physical model, as required for behavioral testing, we hope to identify some design flaws early in the development cycle. The particular system studied, ROBART, is an experimental, interactive color graphics system for creating slides for technical presentations. It is intended to be used by people without computer training. Two comparable versions of the system exist (ROBART 1 and ROBART 2). The two versions have essentially the same function but differ in the the design of the human interface. The paper describes relevant portions of the two ROBART versions in some detail. It then presents a formal description of the ROBART 1 action language and makes predictions about human performance based on the formal description of ROBART 1 and matching parts of ROBART 2. Then, it presents results of exploratory tests of some of the predictions. The potential value of formal description of action languages is discussed, as well as other related work. Extract: Summary Summary The field of human factors is frequently judged to be lacking in rigor. To counteract this judgment, we have shown, by means of a concrete example, that 1) user actions at a terminal can be described by means of a formal grammatical notation, 2) the formalism can be used to make predictions for comparing design alternatives and locating design flaws, and 3) the predictions can be empirically tested. We have given a complete formal description of the ROBART 1 system and then made predictions on the basis of the formal description of ROBART 1 and matching portions of ROBART 2. We predicted that selecting shapes in ROBART 1 would vary in difficulty, that selecting shapes in ROBART 2 would not vary in difficulty, and that selecting any ROBART 2 shape would be easier than selecting the same shape in ROBART 1. These predictions were upheld in objective testing of immediate memory and in subjective questionnaires. We also predicted that users would make errors in attempting to initiate continuous shapes using ROBART 1 and would not make mistakes in ROBART 2. These predictions were also supported in testing. Formal description of interactive systems is an analytic tool. It makes possible the examination of a design from the human point of view early in the design cycle. We can thus compare some aspects of alternative designs and identify some design inconsistencies before a working model is built. The method we have presented is a general one. Other interactive systems (word processors, editors, etc.) can be described by means of a formal notation. The predictions we made were based on general properties of the formal description and the approach should therefore generalize. in IEEE Transactions on Software Engineering, March 1981 view details in IEEE Transactions on Software Engineering, March 1981 view details |