CS 4720

Usability and Accessibility

CS 4720 – Web & Mobile Systems

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What makes a good interface?• Don't say “anything but SIS.”• What are it's characteristics?• How do you just KNOW that you're using

something that has been thought out properly?

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Not Just the UI• The experience begins with the first time you

launch an app or go to a web site• There are several components here

– Initial impression– User interface– 80/20 rule (sometimes the 90/10 rule)– Graphic design– Information presentation

• All of this adds up to the user experience (UX)

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10 Rules…• 10 Rules to Mobile HCI

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Evaluating an Interface• Rule 1: Visibility of system status• The system should always keep users informed

about what is going on through appropriate feedback within reasonable time.

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Evaluating an Interface• Rule 2: Match the system to the real world• The system should follow real-world

conventions, making information appear in natural and logical order.

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Evaluating an Interface• Rule 3: The “uh-oh” button• Users often choose system functions by

mistake (particularly on mobile) and will need a clearly marked “emergency exit” to leave the unwanted state without having to go through extended steps.

• Systems should support undo and redo.

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Evaluating an Interface• Rule 4: Consistency and standards• User should not have to wonder whether

different words, situations, or actions mean the same thing.

• The system should follow platform conventions.

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Evaluating an Interface• Rule 5: Error prevention• Add input checks

– How many digits in that phone number?– How many digits in that credit card number?– Are there really 39 days in July?

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Evaluating an Interface• Rule 6: Recognition rather than recall• An icon should represent the action and should

immediately recognizable as to what it does• Part of this is following platform standards, part

is being consistent in your own application• An action/swipe/etc should be consistent

across screens

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Evaluating an Interface• Rule 7: Flexibility• Accelerators, shortcuts, etc (which are unseen

by the novice user) can speed up interactions for the expert user to such an extent that the system can cater to both inexperienced and experienced users.

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Evaluating an Interface• Rule 8: Aesthetic and minimalist design• Every extra unit of information in a dialog

competes with the relevant units of information and diminishes their relative visibility.

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Evaluating an Interface• Rule 9: Error explanations• Error messages should be expressed in plain

language (NO CODES), precisely indicate the problem, and constructively suggest a solution.

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Evaluating an Interface• Rule 10: Help!• Have reasonable help information available in

the app if possible.

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The Ten Rules• 1. Visibility of Status• 2. System = Real World• 3. The “uh-oh” button• 4. Consistency and Standards• 5. Error Prevention• 6. Recognition rather than Recall• 7. Flexibility• 8. Minimalist Design• 9. Error Explanation• 10. Help!

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Phone-Specific Interface

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• We need to separate two concerns here– The Hardware Interface– The Software Interface

• What are some specific hardware innovations that we use with cell phones?

• How do these address the 10 rules?

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Hardware Interface• Consider the following hardware innovations:

– The click wheel– The rocker– The track ball– The home button

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Software Interface

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• Let's look at a few interfaces

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Image Galleries

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Empty Lists

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Describing Places

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Concepts

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• UI's that grow and shrink– Flexible design

• Softkeys and icon buttons for common tasks• Predictive text• Others?

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One Hand or Two Hands?• Large, obvious buttons• Controls toward the center of the screen so

you don't have to stretch• Controls have space between them if possible• Put only needed items on the screen• Eliminate unnecessary words• Make transitions between states obvious• Apps: Phone, Contacts, Urbanspoon

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One Hand or Two Hands?

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• Theoretically, the user is not moving, so controls can be more complex

• Stylus control• Keyboard in landscape mode (soft or hard)• More information to proces• Apps: Amazon, AllRecipes

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Rules of Thumb

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• Easy traversals between states• Audio sparingly (remember – audio may be

turned off!)• Build for the input device (click wheel, touch

screen, stylus)• Provide shortcuts when possible• Try to use direct-manipulation widgets for input

with immediate feedback• Menus must be tailored to the device input

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Rules of Thumb• Typing isn't easy – provide ways to remember

text• Use contextual information whenever possible

(use GPS coords automatically in a Google search, have the last contact up for making a phone call, etc)

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My UI works great now!• But it still doesn't look “slick!”• Simple is beautiful• Get a friend to pick out the color scheme for

you. Seriously.• Imitation is the greatest form of flattery• If all else fails… ask a graphic design student• Or check the patterns:

– http://sixrevisions.com/user-interface/mobile-ui-design-patterns-inspiration/

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