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A Methodology for User Interface Design
by Charles Irby and Linda Bergsteinsson, ITG Systems Development Division
Thomas Moran, William Newman and. Larry Tesler, Palo Alto Research Center


3333 Coyote Hill Road / Palo Alto / California 94304

3406 Hillview Avenue / Palo Alto / California 94304

This document is for Xerox internal use only

In April 1976, a working group was formed at the Xerox Palo Alto facility to study
the problem of user interface design. . The group was led by Chafles Irby, and
included Linda Bergsteinsson, Tom Moran. William Newman and Larry Tesler as its
other full-time members. The group met on a weekly basis throughout the spring
and summer of ~976. David Liddle and Butler Lampson attended some of the early

User interface design is an essential part' of the design of interactive application
programs. The user interface encompasses the set of commands by which the user
operates the program, the display techniques used to present the state of the
program to him, and the more abstract notions involved in learning how to operate
the program effectively. Successful user interface design is crucial to the
production of useful Office Information Systems.

The working group decided at one of its earliest meetings that it could not attempt
to propose an actual design for an OIS user interface. The reasons for this lie in
the complex nature of user interface design, and the difficulty of performing the
design without a thorough analysis of the task. Theseproblerns are- discussed
further in the main report.

The group therefore concentrated its efforts on developing a straightforward
methodology for user interface design. This methodology is presented in the
report. Included with the report is a detailed description of a user interface
developed along the lines suggested.

The working group will now turn its attention to interaction with the application
designers and subsequent design of the user interface facilities for OIS.


We wish to thank the many people who provided useful comments and suggestions
about this report, in particular D. DeSantis. A. Kay. R. Kimball, T. Mott, R. Sproull
and R. Taylor.


Introduction 2

Task Analysis 2
The Three Components of the User Interface 3
The Design Process 5
Conclusion 8
Appendix 10
Current Task Description 11
User's Conceptual Model 16
New Task Description 21
Data Presentation 24
Scenario 29
Terminal Description 35
Command Language 37
Input Cross Reference 51
Output Cross Reference 52


One of the most troublesome and least understood aspects of interactive systems is
the user interface. In the design of user interfaces, we are concerned with several
issues: the provision of languages by which users can express their commands to the
computer; the design of display representations that show the state of the system to
the user; and other more abstract issues that affect the user's understanding of the
system's behavior. Many of these issues are highly subjective. and are therefore ofte~
addressed in an ad hoc fashion. We believe, however. that more rigorous approaches
to user interface design can be developed; we present such an approach in' this rep0rt.

In preparing this document. our main concern has been to propose a methodology for
us-er interface design~' It based primarily 9n.the separatlonofus.ei. iriter:facedesi~n -
into a small number of separate design phases, to be applied iteratively in order to
reach a satisfactory design. For each of these phases we have developed
representations in which to present the concepts involved; these representations help
both in formalizing the design process, and in defining the user interface design for
purposes of documentation and communication with others. We have included a
number of guidelines that we feel may be useful to those designing user interfaces.
To illustrate the use of our methodology, we have included a partial description of a