What exactly do we mean by user-interface design?
Apparently, it depends on who’s asking, or who’s speaking.
Consider the following events.
Recently, Bill Moggeridge, a well-known product designer,
acknowledged in a keynote address at Designing Interactive
Systems 2002 (DIS 2002), a SIGCHI-sponsored design
conference, that he, assisted by a fellow product designer,
Bill Verplank, invented the concept of interaction design in
the early 1980s. In his review of important contributors to
this term that he never defined but which seemed to include
much of user-interface design, he included a number of
well-known user-interface researchers, as well as founders of
Google, a successful Web-based information search service,
and of Palm’s mobile-device operating system. The term
user interface almost never entered the
About a year ago, Alan Cooper, a well-known software
designer (and inventor of a software language) announced in
the keynote address of the Usability Professionals
Association’s annual conference, that he was the inventor of
the concept of interaction design in the 1980s, a concept
that he, too, never defined in his lecture but that seemed to
include much of user-interface design. He also said that
interaction design (thus, user-interface design) didn’t exist
until he brought it into being.
In recent publications of the American Institute of
Graphic Arts and conferences that it has co-sponsored with
SIGCHI, promoters of a concept called experience
design have proposed that they are designing something
larger than, different from, and more important than
user-interface design. Attempts to define exactly what this
term includes in the promoters’ magazines, books, lectures,
and conferences remain ambiguous thus far.
During a gathering to discuss the newly formed Institute
of Design at the University of California at Berkeley, Arnold
Wasserman, a well-known corporate product designer and
strategist, praised the product design community for having
been the first to emphasize usability rather than the human
factors specialists’ more narrow focus on ergonomic issues.
In doing so, he appeared to overlook the typography and
graphic design community’s contemporaneous investigation of
these same kinds of issues.
During the advent of the Web and the rise, then fall, of
the DotComs, information architecture seemed to be the
new term to describe much, but not all, of user-interface
design. Note, however, that information architects, unlike
their more established cousins, are not licensed to practice.
(Certification for analysts and designers is a complex,
thorny matter that I shall not address here.)
When I first began writing a user-interface design manual
in the late 1970s, I was already aware that there was a topic
of user-interface design. Shortly after that, CHI held its
first conference. Today, product reviews in the Wall
Street Journal and the New York Times comment
regularly on user-interface design. Apparently, these
critics, and presumably the general public, understand the
term user-interface design.
What is going on here? Many reasonably well-educated and
presumably well-meaning professionals seem to be forgetting
history, rewriting history, and muddying conceptual waters
rather than clarifying them.
It seems appropriate on the occasion of SIGCHI’s 20th
anniversary to consider how the profession defines itself,
particularly in its "design" aspects. Of course,
whether SIGCHI should undertake such an activity at all is
debatable to some who worry about which professions are
included and which are not. Others might say, let a thousand
definitions bloom; the more the better.
I take a middle road in trying to be simple, clear, and
consistent in defining the terms. Much is at stake in this
conceptual turf battle. Around the world, institutions of
higher learning are attempting to establish clear pedagogical
objectives and curricula that present a coherent, inclusive
view of user-interface design. More than 10 years ago, SIGCHI
itself tried to describe a user-interface
analysisdesigntheory curriculum for computer
science departments. Now, many professions are involved in
trying to define this complex, challenging topic.
Almost any practical term could replace user-interface
design. However, without clear, consistent, agreed-on
conventions, the terminology may confuse professionals,
teachers, and students, further confusing or boring the
general public, and not effectively reaching the business
community. Some inappropriate terms may become conventions,
which sometimes impoverishes distinctions.
For example, the computer industry, has unfortunately,
obliterated much of the useful distinction of sign,
icon, and symbol. The general semiotics term
sign is casually equated with its subterms icon
(representational, or "natural" sign) and
symbol (abstract or conventional signs). In many
professional situations of analysis and design, these
distinctions are important to maintain. Alas, all of the
small visual signs of user interfaces are now loosely called
icons by professionals as well as the public.
Some of the organizations that have a stake in this
process of defining user interface and design
include the following:
American Institute of Graphic Arts (AIGA)
Association for Computing Machinery (ACM)
ACM Special Interest Group for Computer-Human Interaction
ACM Special Interest Group for Graphics and Interaction
Human Factors and Ergonomics Society
Industrial Design Society of America
International Institute for Information Design
Society for Technical Communication
Society for Software Design
Society for Software Psychology
You may have candidates to add to this list. Professionals
of these and other organizations have considered one or more
of these topics to be the appropriate term for essential
Computer-based communication design
Computer-based theater design
Computer-human interaction design
Human-computer interaction design
Interactive media design
If we are careful in our thinking, we
should be able to translate from one paradigm to another,
appreciating the various complexities and values.
Again, you may have additions to suggest. The terminology
has always been fluid and subject to social, political, and
technological shifts. Recall that manmachine
interface (MMI) was changed to ungendered synonyms during
the late 1980s and early 1990s and that multimedia
became a redundant term by the late 1990s. The availability
of virtual and augmented reality; mobile devices; wearable
computers; and less-noticeable, ubiquitous computers have all
caused theorists, teachers, and professionals to rethink
their terminology and definitions. It is also possible that
well-designed definitions may serve during many changes of
technology, if the terms are well defined.
Here is what seems to me to be a reasonable approach to
defining user-interface design.
First, we should acknowledge that human beings, to
paraphrase the structural anthropologist Claude Levi-Strauss
, are fundamentally tool- and sign-makers.
As artifact makers, we are deeply connected to our wired-in
capabilities; to personal emotional, cognitive, and spiritual
needs and desires; as well as to our sociocultural
constructs. We have been making clothes, hammers, and other
physical tools for countless millennia. We also have been
communicating through physical gesture, touch, sound, smell,
and vision for eons. Tools enable us to change our physical
environment. Written artifacts, including coins, parchment
rolls, and walls, carry messages across space and time in a
way physical gestures and speech cannot.
These aspects of the history of communication are worth
mentioning, because the history of computers itself is
closely enmeshed with the challenge to improve input and
output techniques. What we are addressing essentially is not
solely physical object design, but computer-mediated
User-interface design could be defined from the
perspective of a tool, (physical object) or communication.
Either way, both definitions would include interaction
as a concept. However, it is important to appreciate the full
meaning of user interfaces as communication artifacts. To
call user-interface design interaction design misses some
important points, as seems evident if one listens to
proponents of interaction design.
In Designing Pleasurable Products
, Patrick Jordan presents a property
checklist for designing a power drill. The list includes many
sensory attributes, functionality, and "interaction
design," which is defined elsewhere as interaction
sequences and protocols. The communication dimensions seem to
In the recent keynote lecture I mentioned earlier about
the history of interaction design over the past 20 years,
Bill Verplank mentioned that there is something else besides
interaction design called media design, which is
essentially an "expressive" activity. By
"media," I understand such terms as broadcast
television, video tapes, printed books, comic books, cinema,
CDs, DVDs. In previous centuries, one would mention religious
and governmental architectural sculptural friezes, documents,
and monuments. As communication forms, according to the
definitions of Moles , media convey
information, persuasion, and aesthetics (some might add
spiritual content). Definitions of media by interaction
designers seem to view media as only expressive or aesthetic
or persuasive communication, neglecting the long history of
information-oriented visual communication design, with its
close ties to graphic design, education, government,
commerce, and technology.
Regarding "experience design," it seems that
some graphic designers, media designers, Web designers,
branding and business strategists, and others claim the
design of the interactive experiences of a viewer, customer,
visitor, resident, or reader. This claim seems a bit vague.
What would architects of buildings or landscapes make of
this? Would they not be one of the first to claim the design
of interactive human experience? Those wishing to understand
the work of experience designers might do well to consider
the work of Disney designers, who do, indeed, control the
total experience of visitors to Disney-fabricated
What then are my proposed definitions? I have been
refining them for many years, and I present them below in a
short lexicon. This philosophical perspective emphasizes
communication as a fundamental characteristic of computing,
one that includes perceptual, formal characteristics and
dynamic, behavioral aspects of how people interact through
computer-based media. This approach acknowledges
user-interface design more strongly as a set of communication
design tasks but tries, also, to find places for product and
architectural design. The intention has been to acknowledge
the specific skills of many different artifact-design
profesions. Sound designers, theater designers, graphic
designers, and information designers often seem marginalized
in the definitions that I have encountered. I have tried to
formulate the definition of user-interface design in a manner
that allows it to be inclusive, not exclusive. I have also
tried to define terms so that they can survive the rapid
change of platform technology. The eventual
"disappearance" of computers and the rise of
"smart" objects will always involve communication
rituals. In some ways, we are back where we started 10,000
years ago with the exchange of three-dimensional tokens, but
with many new magnificent twists in our computer-based
I hope you will find this lexicon useful. Others may
propose different perspectives and terms. If we are careful
in our thinking, we should be able to translate from one
paradigm to another, appreciating the varying complexities
and values. Discussing these world views and terminology is a
healthy intellectual, professional exercise. I invite you to
join the ongoing debate.
A Brief User-Interface Lexicon (of Canonical, Reserved Terms)
Appearance: Includes all essential perceptual
attributes, that is, visual, auditory, and tactile
characteristics. Examples include choices of colors, fonts,
animation style, verbal style (such as verbose/terse or
informal/formal), sound cues, and vibration modes.
Communication: The conveyance of information,
persuasion, aesthetics (and, some would add, spiritual
content) from one entity to others. Typically, people
describe, explain, emote, praise, or ritually enact through
their communications. The activity requires senders,
receivers, messages, and media. The process assumes that some
behavior indicates that the receivers have acquired the
messages and understood them.
Information: One level in a hierarchy of organized
content to be communicated. The levels of increasing
complexity are: data, information, knowledge, and wisdom,
described as follows:
Data: Organized input from the senses
Information: Significant patterns of organized
Knowledge: Significant patterns of organized
information with action plans
Wisdom: Significant patterns of organized
knowledge plus real-world experience gained over time.
Information visualization: A special aspect of
user interfaces, the means for communicating
structures and processes, which may be shown in abstract or
representational forms. Classically, these may be described
as tables, forms, charts, maps, and diagrams. The list
suggests an approximately increasing complexity of visual
syntax. This term emphasizes visualization but is intended to
include other sensory means to communicate information.
Interaction: Includes input-output techniques,
status displays, and other feedback, both locally and
globally. In the computer platforms of today, local examples
include the detailed behavior characteristics of equipment,
such as keyboards, mice, pens, or microphones for input;
visual display screens, loudspeakers, or headsets for output;
and the use of drag-and-drop selection and action sequences.
Global examples include context issues, usage scenarios, and
task activities at a larger scale.
Metaphor: Fundamental concepts 
communicated via words, images, sounds, tastes, smells, and
tactile experiences. In computer operating systems, metaphors
substitute for collections or individual elements and help
users understand, remember, and enjoy the entities and
relationships of computer-based communication systems.
Metaphors can be overarching or communicate specific aspects
of user interfaces.
An example of an overarching metaphor is the desktop
meta-phor that substitutes for the computer’s operating
system, functions, and data. Examples of specific concepts
are the trashcan, windows and their controls, pages, shopping
carts, chat rooms, and blogs (Weblogs, or Web-based diaries).
The pace of metaphor invention, including
neologismsthat is, verbal metaphor in-ventionis
likely to increase because of rapid development and
distribution, through the Web and mobile devices, of mutable
products and services. Some researchers are predicting the
end of the desktop metaphor era and the emergence of new
Mental models: Structures or organizations of data,
functions, tasks, roles, and people in groups at work or
play. Examples of related versions of mental models are user
models (which include concepts of personas, goals, needs,
desires, roles, and the like), user cognitive models, user
task models, and designer models. Mental models exhibit
hierarchies of content, tools, specific functions, media,
roles, goals, tasks, and so on. Some professionals speak of
goal-oriented design, user-centered design, task-centered
design. These orientations emphasize close analysis of
varying mental models.
Navigation: Involves movement through the mental
models, that is, through content and tools. Examples of
user-interface elements that facilitate such movement include
those that enable dialogue, such as menus, windows, dialog
boxes, control panels, icons, and tool palettes.
Semiotics: The science of signs
. Semiotics identifies four dimensions of
"meaning" for information visualizations that
communicate through "signs."
Lexical: How are the signs produced?
Syntactic: How are the signs arranged in space and
time and with what perceptual characteristics?
Semantic: To what do the signs refer?
Pragmatic: How are the signs consumed or used?
User interface (UI): A computer-mediated means to
facilitate communication between human beings or between a
human being and an artifact. The user interface embodies both
physical and communicative aspects of input and output, or
interactive activity. The user interface includes both
physical objects and computer systems (hardware and software,
which includes applications, operating systems, and
networks). A user interface may be said to consist of
user-interface components. Reasonable synonyms for user
interface include human-computer interface and human-human
interface. This last term seems appropriate for an era in
which computers themselves disappear, leaving only
"smart" ritual objects and displays, such as
"smart eyeglasses," "smart clothes" and
User-interface components: metaphors,
mental models, navigation, interaction,
User-interface design: The general activity more
properly should be called user-interface development, similar
to software development. Design focuses on the synthesis
User-interface development: User-interface
development consists of these tasks undertaken in a partially
parallel, partially serial, partially iterative sequence:
plan, research, analyze, design, implement, evaluate,
document, train, maintain, and recycle/replace.
User-Interface platform: The user-interface
platform is the physical home of the user interface, that is
of the hardware and software. Traditional examples include
terminals, workstations, desktop computers, Web sites,
Web-based applications, information appliances, and mobile
and wireless devices. However, in general, the platform
encompasses all physical products (consumer or professional)
such as chairs, power drills, tea kettles, tape measures, and
physical environments, such as rooms, buildings, and
Aaron Marcus, President Aaron Marcus and
Associates, Inc. Aaron@AMandA.com
Aaron Marcus (Aaron@AmandA.com) is president of Aaron
Marcus and Associates, Inc., Emeryville, California, and New
York, New York (www.AmandA.com). Mr. Marcus frequently
lectures on user-interface design and has authored or
coauthored four books on the topic.
©2002 ACM 1072-5220/02/0900 $5.00
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