User Interfaces 4

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UNIVERSAL ACCESS• Inclusive design• Interaction styles• Interaction devices• Interface feedback• Response times

Inclusive Design• Adapting existing designs: patchy,

expensive• HCI interaction paradigms applied to

assistive techniques• Guidelines: Can be very theoretical

Some steps for inclusive design

• Adaptation needs to be “designed into‘” the system rather than decided upon and implemented afterwards

• Requires an understanding of the global execution context of a task

• Breaking away from the traditional perspective of “typical” users interacting

• Non-platform specific• Broaden rage of graphical toolkit.

(Stephanidis, C. 2000. Adaptive Techniques for Universal Access. User Modeling and User-Adapted Interaction , 11: 159-179)

Suggested Guidelines• User characteristics: the level of expertise the target

audience have in the subject area of the Web site?• Domain requirements: What is the purpose of the Web

site? What tasks are to be performed using the site?• Technology requirements: browsing and assistive

technology• Pre-existing alternatives: What other ways already

exist to provide access to the information or services of the

Website? (multimedia clips, telephone information line) • Quality of alternatives: What other ways could be

created to provide alternative routes to the same goals to which the site is intended to provide access? What are the accessibility (or other) barriers to accessing these alternative means?

(Sloan, D., Heath, A., Hamilton F., Kelly, B., Petrie, H. and Phipps, L. 2004. Contextual Web Accessibility -Maximizing the Benefit of Accessibility Guidelines [online]. Available at http://www.w4a.info/2006/ [Accessed 1 Sept 2013])

Interaction Styles• Command Line – DOS, NETWORKS• Menus • Natural Language - different nuances• Question/Answer style - Query

language to construct query• Form Fill-in - data capturing• WIMP - Windows, Icons, Menus and

Pointing devices

ExerciseFor each of the previous

interactions styles, list at least 2 advantages and disadvantages

Interaction Styles: Menus

• Single: Binary multiple Item multiple selection pull down and popupscrolling and 2dimensional, alpha sliders embedded links

• Multiple: Linear sequence treeacyclic cyclic

Menu Layout• Titles

for single menus - descriptive title linear sequence - titles should accurately

represent the stages in the sequence tree-structured menus:

• the root must be clearly stated, e.g. MAIN etc.

• use same words in high-level menu items as in titles for next lower level menus

• be consistent with placement of titles

Menu Layout (Cont.)• Phrasing of menu items

Use familiar and consistent terminology

Ensure that items are distinct from one another

Use consistent and concise phrasing

Bring the keyword to the left

• Guide lines for consistency: Titles: centred or left justified Item placement: left, may use blank lines in

between, numbers Instructions: identical, same position Error messages: consistent position, terminology

and syntax Status reports: consistent position and structure

• Progression Successive menus can be cascades, walking

or transparent menus. Walking menus can present a motor challenge. Transparent menus should not be higher than 50%.

Menu Layout (Cont.)

Interaction Devices• Keyboards – qwerty, audio feedback• Pointing Devices:

direct: light pen, touch screen indirect: mouse, trackball, joystick, touchpad

• Touch screen:Smudges, hand obscures, accuracy

• Speech recognition and generation• Gaming devices

Interaction: Speech• Discrete-word recognition

Individual words spoken by specific personWhen/where: handicapped people, speaker’s hand are busy, mobility is required, speaker’s eyes are occupied, harsh or cramped conditions preclude keyboardBackground noise influences accuracy

• Continuous-speech recognitionDictating letter, limited

Speech (Cont.)• Speech store and forward

messages stored and forwarded like weather, airlines, voice mail, audio tours in museums

• Speech generationWhen: message is simple, short, will not be referred to later, deals with events in time, requires an immediate response, visual

Interface Feedback• Error Messages• Colour• Design• Data display

Feedback: Error Messages

Phrasing of error messages or diagnostic warnings is critical:• Why do users make errors?: lack of

knowledge, incorrect understanding, inadvertent slips

• Errors lead to feelings of inadequacy, confusion and anxiety

• Too imperious tone condemning the user increases anxiety resulting in further errors

• Too generic messages don’t give enough information to correct the error

• Obscure messages like FAC RJCT 0004444 offer no assistance.

Guidelines for error messages

• Be specific about what caused the error: e.g. • Use constructive guidance and positive tone,

the user needs guidance to correct the error• User-Centered phrasing: don’t use ENTER

DATA, rather use READY TO ACCEPT DATA• Appropriate physical format: Reserve capital

letters for serious warnings, avoid using error codes, placement of error messages

• Develop effective error messages by involving the users

ILLEGAL ENTRY Type first letter: Send, Read, or Drop

• Multiple levels of messages• Consistent grammatical form, terminology

and abbreviations• Consistent visual format and placement

Exercise:Find at least 3 error messages in any

applications and evaluate them against these guidelines.

Guidelines for error messages(Cont.)

Feedback: Colour• Place colour coding under user control• Consider the needs of colour-deficient users• Limit the number of colours no more than 4• Use colour as a coding technique, e.g. all

addresses a particular colour, or all labels one colour and all data-entry fields another

• Ensure that colour coding supports the task, e.g. the active window a different colour from the inactive one, when status of an item changes, change its colour

• Common expectations about colour codes, e.g. warning messages in red – cultural!!!

Feedback: DesignNon-anthropomorphic Design• avoid presenting computers as people• choose appropriate humans for introductions and

guidelines (culturally and gender sensitive)• use caution in designing computer-generated

human faces or cartoon characters• design comprehensible, predictable and controllable

interfaces• provide user-centred overviews for orientation and

closure• do not use “I” when the computer responds to human

actions• use “you” to guide users or just state facts

Feedback: Data Display

• Keep complexity low• directly usable form• order lists • label each page in multi-paged display• maintain consistent format

Response Times• Response Time = the number of seconds it takes

from the moment the user initiates an activity until the computer begins to present results.

• User Think Time = the number of seconds during which users think before entering the next action.

• Users plan while reading results, while typing, and while the computer is generating results or retrieving information across a network.

• Precise measurement of User Think Time is difficult. Measurement of computer response time is easier, but distracting messages, informative feedback, etc. also influence results.

• Factors influencing choice of optimum speed:o experience: novices may need slower response times,

experienced users require rapid actiono penalty for errors: if low penalty for errors then users

prefer to work fastero task: typing, frequent, data capturing, problem solving

tasks require different response times• Expectations and attitude

o How long will users wait before becoming agitated? Varies

o past experiences, varied response times for same task promotes agitation

o delay tolerance: personality, age, cost, mood, culture, pressure, etc.

o task complexity difference

Response Times (cont.)

• Variabilityo users can adapt to variable situation: some

take advantage of ito modest variations in response time (plus or

minus 50%) appear to be tolerable with little effect on performance

o with extreme changes users are able to adapt and complete their tasks, but frustration emerges.

Response Times (cont.)

• Users prefer shorter response times• Longer response times (> 15 sec) are disruptive• Users change usage profile with response time• Shorter response time leads to shorter think time• A faster pace may increase productivity, but may increase

error rates• Error recovery ease and time influence optimal response time• Response time should be appropriate for the task:

o Typing, cursor motion, mouse selection: 50-150 millisecondso simple frequent tasks: 1 secondo common tasks: 2-4 secondso complex tasks: 8-12 seconds

• Users should be advised of long delays• Modest variability in response time is acceptable• Unexpected delays may be disruptive• Empirical tests can help to set suitable response times

Response Time Guidelines