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As the aim of this lecture is to introduce you the study of Human Computer
Interaction, so that after studying this you will be able to:

. Understand the Principles of visual interface design

39.1 Provide visual structure and flow at each level of

Your interfaces are most likely going to be composed of visual and behavioral
elements used in f groups, which are then grouped together into panes, which then may, in
turn, be grouped into screens or pages. This grouping can be by position (or proximity), by
alignment, by color (value, hue, temperature, saturation), by texture, by size, or by shape.
There may be several such levels of structure in a sovereign application, and so it is critical
that you maintain a clear visual structure so that the user can easily navigate from one part of
your interface to another, as his workflow requires. The rest of this section describes
several important attributes that help define a crisp visual structure.

Alignment; grids, and the user's logical path

Alignment of visual elements is one of the key ways that designers can help users
experienced product in an organized, systematic way. Grouped elements should be aligned
both horizontally and vertically (see Figure).

In particular, designers should take care to

. Align labels. Labels for controls stacked vertically should be aligned with each other;
left-justification is easier for users to scan than right justification, although the latter may
look visually cleaner — if the input forms are the same size. (Otherwise, you get a
Christmas tree, ragged-edge effect on the left and right.)

. Align within a set of controls. A related group of check boxes, radio buttons, or text ,
fields should be aligned according to a regular grid.

. Align across controls. Aligned controls (as described previously) that are grouped
together with other aligned controls should all follow the same grid.

. Follow a regular grid structure for larger-scale element groups, panes, and
screens, as well as for smaller grouping of controls.
A grid structure is particularly important for defining an interface with several levels of visual or
functional complexity. After interaction designers have defined the overall framework for the
application and its elements, visual interface designers should help regularize the layout
into a grid structure that properly emphasizes top-level elements and structures but still
provides room for lower level or less important controls. The most important thing to remember
about grids is that simple is better. If the atomic grid unit is too small, the grid will become
unrecognizable in its complexity. Ambiguity and complexity are the enemies of good
design. Clear, simple grids help combat ambiguity.

The layout, although conforming to the grid, must also properly mirror the user's
logical path through the application, taking into account the fact that (in Western
countries) the eye will move from top to bottom and left to right (see Figure).


Symmetry1 is a useful tool in organizing interfaces from the standpoint of providing
visual balance. Interfaces that don't employ symmetry tend to look unbalanced, as if they are
going to topple over to one side. Experienced visual designers are adept at achieving
asymmetrical balance by controlling the visual weight ot individual elements much as
you might balance children of different weights on a seesaw. Asymmetrical design is
difficult to achieve in the context of user interfaces because of the high premium placed
on white space by screen real-estate constraints. The squint test, the mirror test, and the
upside down test are again useful for seeing whether a display looks lopsided.
Two types of symmetry are most often employed in interfaces: vertical axial symmetry (symmetry
along a vertical line, usually drawn down the middle of a group of elements) or diagonal axial
symmetry (symmetry along a diagonal line). Most typical dialog boxes exhibit one or the other
of these symmetries — most frequently diagonal symmetry (see Figure).

Sovereign applications typically won't exhibit such symmetry' at the top level (they
achieve balance through a well-designed grid), but elements within a well-designed
sovereign interface will almost certainly exhibit use of symmetry' to some degree (see Figure).


Spatial harmony considers the interface (or at least each screen) as a whole. Designers
have discovered that certain proportions seem to be more pleasing than others to the
human eye. The best known of these is the (Golden Section ratio, discovered in antiquity —
likely by the Greeks —and probably coined by Leonardo Da Vinci. Unfortunately, for
the time being, most computer monitors have a ratio of 1.33:1, which puts visual
designers at a bit of a disadvantage when laying out full-screen, sovereign
applications. Nonetheless, the understanding of such ratios makes a big difference in
developing comfortable layouts for user interfaces.
Proper dimensioning of interface functional regions adds to spatial harmony, as does a
proper amount of white space between elements and surrounding element groups. Just as
well-designed books enforce proper margins and spacing between paragraphs, figures,
and captions, the same kind of visual attention is critical to designing an interface that does
not seem cramped or uncomfortable. Especially in the case of sovereign applications, which
users will be inhabiting for many hours at a time, it is critical to get proportions right. The
last thing you want is for your user to feel uncomfortable and irritated every time she uses
your product or service. The key is to be decisive in your layout. Almost a square is no good.
Almost a double square is also no good. Make your proportions bold, crisp, and exact.


Use cohesive, consistent, and contextually appropriate imagery

Use of icons and other illustrative elements can help users understand an interface,
or if poorly executed, can irritate, confuse, or insult. It is important that designers
understand both what the program needs to communicate to users and how users think
about what must be communicated. A good understanding of personas and their mental
models should provide a solid foundation for both textual and visual language used in an
interface. Cultural issues are also important. Designers should be aware of different
meanings for colors in different cultures (red is not a warning color in China), for gestures
(thumbs up is a terrible insult in Turkey), and for symbols (an octagonal shape means a
stop in the US, but not in many other countries). Also, be aware of domain-specific
color coding. Yellow means radiation in a hospital. Red usually means something lifethreatening.
Make sure you understand the visual language of your users' domains and
environments before forging ahead.
Visual elements should also be part of a cohesive and globally applied visual
language. This means that similar elements should share visual attributes, such as how
they are positioned, their size, line weight, and overall style, contrasting only what is
important to differentiate their meaning. The idea is to create a system of elements that
integrate together to form a cohesive whole. A design that achieves this seems to fit together
perfectly; nothing looks stuck on at the last minute.


Designing icons to represent functions or operations performed on objects leads to
interesting challenges. The most significant challenge is to represent an abstract
concept in iconic, visual language. In these cases, it is best to rely on idioms rather than
force a concrete representation where none makes sense and to consider the addition of
ToolTips or text labels. For more obviously concrete functions, some guidelines apply:

. Represent both the action and an object acted upon to improve comprehension.
Nouns and verbs are easier to comprehend together than verbs alone (for example,
for a Cut command, representing a document with an X through it may be more
readily understood than a more metaphorical image of a pair of scissors).

. Beware of metaphors and representations that may not have the intended
meanings for your target audience.

. Group related functions visually to provide context, either spatially or, if this
is not appropriate, using color or other common visual themes.

. Keep icons simple; avoid excessive visual detail.

. Reuse elements when possible, so users need to learn them only once.


Creating unique symbols for types of objects in the interface supports user
recognition. These symbols can't always be representational or metaphoric — they are
thus often idiomatic. Such visual markers help the user navigate to appropriate objects
faster than text labels alone would allow. To establish the connection between symbol
and object, use the symbol wherever the object is represented on the screen.



Especially as the graphics capabilities of color screens increase, it is tempting to
render icons and visuals with ever-increasing detail, producing an almost photographic
quality. However, this trend does not ultimately serve user goals, especially in productivity
applications. Icons should remain, simple and schematic, minimizing the number of colors
and shades and retaining a modest size. Both Windows XP and Mac OS X have recently
taken the step towards more fully rendered icons (OS X more so, with its 128x128 pixel,
nearly photographic icons). Although such icons may look great, they draw undue attention
to themselves and render poorly at small sizes, meaning that hey must necessarily take up
extra real estate to be legible. They also encourage a lack of visual cohesion in the interface
because only a small number of functions (mostly those related to hardware) can be
adequately represented with such concrete photo-realistic images. Photographic cons are
like all-capitalized text; the differences between icons aren't sharp and easy to distinguish,
so we get lost in the complexity. The Mac OS X Aqua interface is filled with photo-realistic
touches that ultimately distract. None of this serves the user particularly well.


Instead of using words alone to describe the results of interface functions (or worse,
not giving any description at all), use visual elements to show the user what the results will
be. Don't confuse this with use of icons on control affordances. Rather, in addition to using
text to communicate a setting or state, render an illustrative picture or diagram that
communicates the behavior. Although visualization often consumes more space, its
capability to clearly communicate is well worth the pixels. In recent years, Microsoft has
discovered this fact, and the dialog boxes in Windows Word, for example, have begun to
bristle with visualizations of their meaning in addition to the textual controls. Photoshop
and other image-manipulation applications have long shown thumbnail previews of the
results of visual processing operations The Word Page Setup dialog box offers an image
labeled Preview. This is an output-only control, showing a miniature view of what the page
will look like with the current margin settings on the dialog. Most users have trouble
visualizing what a 1.2 inch left margin looks like. The Preview control shows them.
Microsoft could go one better by allowing input on the Preview control in addition to
output. Drag the left margin of the picture and watch the numeric value in the corresponding
spinner ratchet up and down.
The associated text field is still important — you can't just replace it with the visual
one. The text shows the precise values of the settings, whereas the visual control
accurately portrays the look of the resulting page.

Integrate style and function comprehensively and purposefully

When designers choose to apply stylistic elements to an interface, it must be from a
global perspective. Every aspect of the interface must be considered from a stylistic point of
view, not simply individual controls or other visual elements. You do not want your
interface to seem as though someone applied a quick coat of paint. Rather you need to
make sure that the functional aspects of your program's visual interface design are in
complete harmony with the visual brand of your product. Your program's behavior is part of
its brand, and your user's experience with your product should reflect the proper balance of
form, content, and behavior.



Although visual style is a tempting diversion for many visual designers, use of
stylized visual elements needs to be carefully controlled within an interface —
particularly when designing for sovereign applications. Designers must be careful not to
affect the basic shape, visual behavior, and visual affordance of controls in the effort to
adapt them to a visual style. The point is to be aware of the value each element provides.
There's nothing wrong with an element that adds style, as long as it accomplishes what you
intend and doesn't interfere with the meaning of the interface or the user's ability to interact
with it.
That said, educational and entertainment applications, especially those designed for
children, leave room for a bit more stylistic experimentation. The visual experience of
the interface and content are part of the enjoyment of these applications, and a greater
argument can also be made for thematic relationships between controls and content. Even
in these cases, however, basic affordances should be preserved so that users can, in fact, reach
the content easily.


Most successful companies make a significant investment in building brand equity. A
company that cultivates substantial brand equity can command a price premium for its
products, while encouraging greater customer loyalty. Brands indicate the positive
characteristics of the product and suggest discrimination and taste in the user.
In its most basic sense, brand value is the sum of all the interactions people have with a
given company. Because an increasing number of these interactions are occurring
through technology-based channels, it should be no surprise that the emphasis placed on
branding user interfaces is heater than ever. If the goal is consistently positive customer
interactions, the verbal, visual, and behavioral brand messages must be consistent.
Although companies have been considering the implications of branding as it relates
to traditional marketing and communication channels for some time now, many
companies are just beginning to address branding in terms of the user interface. In
order to understand branding in the context of the user interface, it can be helpful to think
about it from two perspectives: the first impression and the long-term relationship.
Just as with interpersonal relationships, first impressions of a user interface can be
exceedingly important. The first five-minute experience is the foundation that long-term
relationships are built upon. To ensure a successful first five-minute experience, a user
interface must clearly and immediately communicate the brand. Visual design,
typically, plays one of the most significant roles in managing first impressions largely
through color and image. By selecting a color palette and image style for your user interface

that supports the brand, you go a long way toward leveraging the equity of that brand
in the form of a positive first impression.
After people have developed a first impression, they begin to assess whether the
behavior of the interface is consistent with its appearance. You build brand equity and
long-term customer relationships by delivering on the promises made during the first
impression. Interaction design and the control of behavior are often the best ways to
keep the promises that visual branding makes to users.


39.2 Principles of Visual Information Design

Like visual interface design, visual information design also has many principles that
the prospective designer can use to his advantage. Information design guru Edward Tufte
asserts that good visual design is "clear thinking made visible," and that good visual design
is achieved through an understanding of the viewer's "cognitive task" (goal) and a set of design
Tufte claims that there are two important problems in information design:

1. It is difficult to display multidimensional information (information with more than
two variables) on a two-dimensional surface.

2. The resolution of the display surface is often not high enough to display dense
information. Computers present a particular challenge — although they can add
motion and interactivity, computer displays have a low information density
compared to that of paper.
Interaction and visual interface designers may not be able to escape the limitations of
2D screens or overcome the problems of low-resolution displays. However, some
universal design principles — indifferent to language, culture, or time — help maximize
the effectiveness of any information display, whether on paper or digital media.
In his beautifully executed volume, The Visual Display of Quantitative Information
(1983), Tufte introduces seven Grand Principles, which we briefly discuss in the following
sections as they relate specifically to digital interfaces and content.
Visually displayed information should, according to Tufte

1. Enforce visual comparisons

2. Show causality

3. Show multiple variables

4. Integrate text, graphics, and data in one display

5. Ensure the quality, relevance, and integrity of the content

6. Show things adjacently in space, not stacked in time

7. Not de-quantify quantifiable data
We will briefly discuss each of these principles as they apply to the information
design of software-enabled media.

Enforce visual comparisons

You should provide a means for users to compare
related variables and trends or to compare before and
after scenarios. Comparison provides a context that
makes the information more valuable and more
comprehensible to users. Adobe Photoshop, along with
many other graphics tools, makes frequent use of
previews, which allow users to easily achieve before
and after comparisons interactively (see Figure A as
well as Figures B and C).

Show causality

Within information graphics, clarify cause and effect.
In his books, Tufte provides the classic example of the
space shuttle Challenger disaster, which could have been

averted if charts prepared by NASA scientists had been organized to more clearly present the
relationship between air temperature at launch and severity of 0-ring failure. In interactive
interfaces, modeless visual feedback should be employed to inform users of the potential
consequences of their actions or to provide hints on how to perform actions.

Show multiple variables

Data displays that provide information on multiple, related variables should be able to
display them all simultaneously without sacrificing clarity.
In an interactive display, the user should be able to
selectively turn off and on the variables to make
comparisons easier and correlations (causality) clearer. Figure B shows an example of an
interactive display that permits manipulation of multiple variables.
Figure A
Figure B


Integrate text, graphics, and data in one display

Diagrams that require separate keys or legends to decode are less effective and require
more cognitive processing on the part of users. Reading and deciphering diagram legends
is yet another form of navigation-related excise. Users must move their focus back and forth
between diagram and legend and then reconcile the two in their minds. Figure C shows an
interactive example (integrates text, graphics, and data, as well as input and output: a highly
efficient combination for users.

Ensure the quality, relevance, and integrity of the content

Don't show information simply because it's technically possible to do so. Make sure
that any information you display will help your users achieve particular goals that are
relevant to their context. Unreliable or otherwise poor-quality information will damage the
trust you must build with users through your product's content, behavior, and visual brand.

Show things adjacently in space, not stacked in time

If you are showing changes over time, it's much easier for users to understand the
changes if they are shown adjacently in space, rather than superimposed on one
another. Cartoon strips are a good example of showing flow and change over time
arranged adjacently in space.
Of course, this advice applies to static information displays; in software, animation
can be used even more effectively to show change over time, as long as technical issues
(such as memory constraints or connection speed over the Internet) don't come into play.

Don't de-quantify quantifiable data

Although you may want to use graphs and charts to make perception of trends and
other quantitative information easier to grasp, you should not abandon the display of the
numbers themselves. For example, in the Windows Disk Properties dialog, a pie chart is
displayed to give users a rough idea of their tree disk space, but the numbers of kilobytes
free and used are also displayed in numerical form.

39.3 Use of Text and Color in Visual Interfaces

Text and color are both becoming indispensable elements of the visual language of user
interfaces (text always has been). This section discusses some useful visual principles
concerning the use of these two important visual tools.
Figure C


Use of text

Humans process visual information more easily than they do textual information,
which means that navigation by visual elements is faster than navigation by textual
elements. For navigation purposes, text words are best considered as visual elements.
They should, therefore, be short, easily recognized, and easily remembered.
Text forms a recognizable shape that our brains categorize as a visual object. Each
word has a recognizable shape, which is why WORDS TYPED IN ALL CAPITAL
LETTERS ARE HARDER TO READ than upper/lowercase — the familiar patternmatching
hints are absent in capitalized words, so we must pay much closer attention
to decipher what is written. Avoid using all caps in your interfaces.
Recognizing words is also different from reading, where we consciously scan the
individual words and interpret their meaning in context. Interfaces should try to
minimize the amount of text that must be read in order to navigate the interface
successfully: After the user has navigated to something interesting, he should be able
to read in detail if appropriate. Using visual objects to provide context facilitates
navigation with minimal reading.
Our brains can rapidly differentiate objects in an interface if we represent what
objects are by using visual symbols and idioms. After we have visually identified the
type of object we are interested in, we can read the text to distinguish which particular
object we are looking at. In this scheme, we don't need to read about types of objects
we are not interested in, thus speeding navigation and eliminating excise. The
accompanying text only comes into play after we have decided that it is important.
When text must be read in interfaces, some guidelines apply:

. Make sure that the text is in high contrast with the background and do not use
conflicting colors that may affect readability.

. Choose an appropriate typeface and point size. Point sizes less than 10 are difficult
to read. For brief text, such as on a label or brief instruction, a crisp sans-serif font,
like Arial, is appropriate; for paragraphs of text, a serif font, like Times, is more

. Phrase your text to make it understandable by using the least number of words
necessary to clearly convey meaning. Phrase clearly, and avoid abbreviation. If you
must abbreviate, use standard abbreviations.

Use of color

Color is an important part of most visual interfaces whose technology can support it.
In these days of ubiquitous color LCDs, users have begun to expect color screens even in
devices like PDAs and phones. However, color is much more than a marketing checklist
item; it is a powerful information design and visual interface design tool that can be used
to great effect, or just as easily abused.
Color communicates as part of the visual language of an interface, and users will
impart meaning to its use. For non-entertainment, sovereign applications in particular,
color should integrate well into the other elements of the visual language: symbols and
icons, text, and the spatial relationships they maintain in the interface. Color, when used
appropriately, serves the following purposes in visual interface design:

. Color draws attention. Color is an important element in rich visual feedback,
and consistent use of it to highlight important information provides an important
channel of communication.


. Color improves navigation and scanning speed. Consistent use of color in
signposts can help users quickly navigate and home in on information they are
looking for.

. Color shows relationships. Color can provide a means of grouping or relating
objects together.

Misuse of color

There are a few ways that color can be misused in an interface if one is not careful. The
most common of these misuses are as follows:

. Too many colors. A study by Human Factors International indicated that one
color significantly reduced search time. Adding additional colors provides less
value, and at seven or more, search performance degraded significantly. It isn't
unreasonable to suspect a similar pattern in any kind of interface navigation.

. Use of complementary colors. Complementary colors are the inverse of each
other in color computation. These colors, when put adjacent to each other or when
used together as figure and ground, create perceptual artifacts that are difficult to
perceive correctly or focus on. A similar effect is the result of chromostereopsis, in
which colors v on the extreme ends of the spectrum "vibrate" when placed
adjacently. Red text on a blue background (or vice versa) is extremely difficult to

. Excessive saturation. Highly saturated colors tend look garish and draw too much
attention. When multiple saturated colors are used together, chromostereopsis
and other perceptual artifacts often occur.

. Inadequate contrast. When figure colors differ from background colors only in
hue, but not in saturation or value (brightness), they become difficult to perceive.
Figure and ground should vary in brightness or saturation, in addition to hue, and
color text on color backgrounds should also be avoided when possible.

. Inadequate attention to color impairment. Roughly ten percent of the male
population has some degree of color-blindness. Thus care should be taken when
using red and green hues (in particular) to communicate important information.
Any colors used to communicate should also vary by saturation or brightness to

. distinguish them from each other. If a grayscale conversion of your color

. palette is easily distinguishable, colorblind users should be able to distinguish the
color version.

39.4 Consistency and Standards

Many in-house usability organizations view themselves, among other things, as the
gatekeepers of consistency in digital product design. Consistency implies a similar
look, feel, and behavior across the various modules of a software product, and this is
sometimes extended to apply across all the products a vendor sells. For at-large software
vendors, such as Macromedia and Adobe, who regularly acquire new software titles from
smaller vendors, the branding concerns of consistency take on a particular urgency. It is
obviously in their best interests to make acquired software look as though it belongs, as a
first-class offering, alongside products developed in-house. Beyond this, both Apple and
Microsoft have an interest in encouraging their own and third-party developers to create
applications that have the look and feel of the OS platform on which the program is being
run, so that the user perceives their respective platforms as providing a seamless and
comfortable user experience.


Benefits of interface standards

User interface standards provide benefits that address these issues, although they
come at a price. Standards provide benefits to users when executed appropriately.
According to Jakob Nielsen (1993), relying on a single interface standard improves users'
ability to quickly learn interfaces and enhances their productivity by raising throughput
and reducing errors. These benefits accrue because users are more readily able to predict
program behavior based on past experience with other parts of the interface, or with other
applications following similar standards.
At the same time, interface standards also benefit software vendors. Customer
training and technical support costs are reduced because the consistency that standards
bring improves ease of use and learning. Development time and effort are also
reduced because formal interface standards provide ready-made decisions on the
rendering of the interface that development teams would otherwise be forced to debate
during project meetings. Finally, good standards can lead to reduced maintenance costs
and improved reuse of design and code.

Risks of interface standards

The primary risk of any standard is that the product that follows it is only as good as
the standard itself. Great care must be made in developing the standard in the first place
to make sure, as Nielsen says, that the standard specifies a truly usable interface, and that it
is usable by the developers who must build the interface according to its specifications.
It is also risky to see interface standards as a panacea for good interfaces. Most interface
standards emphasize the syntax of the interface, its visual look and feel, but say little
about deeper behaviors of the interface or about its higher-level logical and
organizational structure. There is a good reason for this: A general interface standard has
no knowledge of context incorporated into its formalizations. It takes into account no
specific user behaviors and usage patterns within a context, but rather focuses on general
issues of human perception and cognition and, sometimes, visual branding as well. These
concerns are important, but they are presentation details, not the interaction framework
upon which such rules hang.

Standards, guidelines, and rules of thumb

Although standards are unarguably useful, they need to evolve as technology and our
understanding of users and their goals evolve. Some practitioners and programmers
invoke Apple's or Microsoft's user interface standards as if they were delivered from Mt.
Sinai on a tablet. Both companies publish user interface standards, but both companies also
freely and frequently violate them and update the guidelines post facto. When Microsoft
proposes an interface standard, it has no qualms about changing it for something better
in the next version. This is only natural — interface design is still in its infancy, and it is
wrongheaded to think that there is benefit in standards that stifle true innovation. In some
respects, Apple's dramatic visual shift from'OS 9 to OS X has helped to dispel the notion
among the Mac faithful that interface standards are etched in granite.
The original Macintosh was a spectacular achievement precisely because it transcended
all Apple's previous platforms and standards. Conversely, much of the strength of the
Mac came from the fact that vendors followed Apple's lead and made their interfaces
look, work, and act alike. Similarly, many successful Windows programs are unabashedly
modeled after Word, Excel, and Outlook.
interface standards are thus most appropriately treated as detailed guidelines or rules of
thumb. Following interface guidelines too rigidly or without careful consideration of

the needs of users in context can result in force-fitting an application's interface into
an inappropriate interaction model.

When to violate guidelines

So, what should we make of interface guidelines? Instead of asking if we should
follow standards, it is more useful to ask: When should we violate standards? The
answer is when, and only when, we have a very good reason.
But what constitutes a very good reason? Is it when a new idiom is measurably better?
Usually, this sort of measurement can be quite elusive because it rarely reduces to a
quantifiable factor alone. The best answer is: When an idiom is clearly seen to be
significantly better by most people in the target user audience (your personas) who try
it, there's a good reason to keep it in the interlace. This is how the toolbar came into
existence, along with outline views, tabs, and many other idioms. Researchers may
have been examining these artifacts in the lab, but it was their useful presence in realworld
software that confirmed the success.
Your reasons for diverging from guidelines may ultimately not prove to be good
enough and your product may suffer. But you and other designers will learn from the
mistake. This is what Christopher Alexander (1964) calls the "unselfconscious
process," an indigenous and unexamined process of slow and tiny forward increments
as individuals attempt to improve solutions. New idioms (as well as new uses for old
idioms) pose a risk, which is why careful, goal-directed design and appropriate testing
with real users in real working conditions are so important.

Consistency and standards across applications

Using standards or guidelines has special challenges when a company that sells
multiple software titles decides that all its various products must be completely
consistent from a user-interface perspective.
From the perspective of visual branding, as discussed earlier, this makes a great deal
of sense, although there are some intricacies. If an analysis of personas and markets
indicates that there is little overlap between the users of two distinct products and that
their goals and needs are also quite distinct, you might question whether it makes
more sense to develop two visual brands that speak specifically to these different
customers, rather than using a single, less-targeted look. When it comes to the
behavior of the software, these issues become even more urgent. A single standard
might be important if customers will be using the products together as a suite. But
even in this case, should a graphics-oriented presentation application, like
PowerPoint, share an interface structure with a text processor like Word? Microsoft's
intentions were good, but it went a little too far enforcing global style guides.
PowerPoint doesn't gain much from having a similar menu structure to Excel and
Word, and it loses quite a bit in ease-of-use by conforming to an alien structure that
diverges from the user's mental models. On the other hand, the designers did draw the
line somewhere, and PowerPoint does have a slide-sorter display, an interface unique
to that application.
Designers, then, should bear in mind that consistency doesn't imply rigidity,
especially where it isn't appropriate. Interface and interaction style guidelines need to
grow and evolve like the software they help describe. Sometimes you must bend the
rules to best serve your users and their goals (and sometimes even your company's
goals). When this has to happen, try to make changes and additions that are

compatible with standards. The spirit of the law, not the letter of the law, should be
your guide.

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