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GUIDELINES FOR DESIGNING USER INTERFACE SOFTWAREESD-TR-86-278

by Sidney L. Smith and Jane N. Mosier 

Introduction |   Data Entry |  Data Display |  Sequence Control |  User Guidance |   Data Transmission |   Data Protection |   Table of Contents

2 DATA DISPLAY

Data display refers to computer output of data to a user, and assimilation of information fromsuch outputs. Some kind of display output is needed for all information handling tasks. Datadisplay is particularly critical in monitoring and control tasks. Data may be output on electronicdisplays, or hardcopy printouts, or other auxiliary displays and signaling devices including voiceoutput, which may alert users to unusual conditions.

In this discussion, data are considered to be display elements related to a user's informationhandling task. Displayed data might consist of stock market quotations, or the current positionof monitored aircraft, or a page of text, or a message from another user. Displayed data mightprovide guidance to a user in performing a maintenance task, or might provide instruction to auser who is trying to learn mathematics or history.

There might be some display elements that themselves do not constitute task-related data.Those elements include labels, prompts, computer-generated advisory messages and other guidance that helps a user interact with a computer system. Although such user guidancedisplay features are sometimes mentioned here in connection with data display, they arediscussed more extensively in Section 4 of these guidelines.

In general, somewhat less is known about data display, and information assimilation by theuser, than about data entry. In current information system design, display formatting is an art.Guidelines are surely needed. But these guidelines may simply serve to help a designer become more proficient in the art.

It must be recognized that guidelines cannot tell a designer what the specific contents of adisplay should be, but only how those contents should be presented. The specific data thatmust be displayed can only be determined through a careful  task analysis to define the user'sinformation requirements.

For effective task performance, displayed data must be relevant to a user's needs. An earlystatement (Smith, 1963b, pages 296-297) of the need for relevance in data display, althoughwritten before common adoption of gender-free wording, otherwise seems valid still: When weexamine the process of man-computer communication from the human point of view, it is usefuto make explicit a distinction which might be described as contrasting "information" with "data."Used in this sense, information can be regarded as the answer to a question, whereas data arethe raw materials from which information is extracted. A man's questions may be vague, suchas, "What's going on here?" or "What should I do now?" Or they may be much more specific.But if the data presented to him are not relevant to some explicit or implicit question, they willbe meaningless. . . . What the computer can actually provide the man are displays of data.What information he is able to extract from those displays is indicated by his responses. How

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effectively the data are processed, organized, and arranged prior to presentation will determinehow effectively he can and will extract the information he requires from his display. Toofrequently these two terms data and information are confused, and the statement, "I need moreinformation," is assumed to mean, "I want more symbols." The reason for the statement,usually, is that the required information is not being extracted from the data. Unless theconfusion between data and information is removed, attempts to increase information in adisplay are directed at obtaining more data, and the trouble is exaggerated rather than relieved.

Certainly this distinction between data and information should be familiar to psychologists, whomust customarily distinguish between a physical stimulus (e.g., "intensity" of a light) and itsperceived effect ("brightness"). The distinction is not familiar to system designers, however,although the issue itself is often addressed. In the following description of what has been calledthe "information explosion", notice how the terms data and information are usedinterchangeably, confounding an otherwise incisive and lively analysis by Martin (1973, page6): The sum total of human knowledge changed very slowly prior to the relatively recentbeginnings of scientific thought. But it has been estimated that by 1800 it was doubling every 50years; by 1950, doubling every 10 years; and by 1970, doubling every 5 years. . . . This is amuch greater growth rate than an exponential increase. In many fields, even one as old asmedicine, more reports have been written in the last 20 years than in all prior human history.

 And now the use of the computer vastly multiplies the rate at which information can begenerated. The weight of the drawings of a jet plane is greater than the