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Published byHelena Short Modified over 9 years ago
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COMP 3715 Spring 05
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Computer Interface Interaction between human and computer Has to deal with two things User’s mental model Different user has different models The state of the computer Need to adapt to different user’s need
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Interface design principles Naturalness Consistency Relevance Supportiveness Flexibility
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Naturalness Intuitive to user Natural language Minimize IT jargon But jargon related to the task ok Instructional, not personal Self-explanatory Minimize human pre/post-process Need to adopt to user
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Consistency Input format Output format Menu layout Messages No surprises!
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Relevance No redundancy Minimize required input Key strokes Minimize required information Minimize output messages Unnecessary information Irrelevant information scare users
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Supportiveness Need adequate information to user Enough feedback to user Need to determine the user’s need Novice vs. Expert
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Flexibility Need to accommodate differences User preference User requirement User expertise Personalization But, more personalization = less help among users Need a way to restore and remember
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Interaction style – command language E.g. DOS prompt, UNIX prompt Typically restricted language set (list of commands) Commands with modifiers/parameters Advantages: Flexibility Speed for expert users Feeling of control Disadvantages Non-supportive Not necessarily natural
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Interaction style – command language Design questions What should be the legal command? Long form vs. abbreviation Error messages need to be supportive Hierarchy of commands? Learning curve
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Interaction style Graphical user interface Question and answer Menu Form
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Interaction style -- GUI Question and answer System ask question, user answers, system decide what to do next Answer can be in different formats Choices: radio buttons, acceptable characters Free form Advantages: Moderately supportive Flexible: short-cuts, various input types Disadvantages Can be tedious if not careful Problem of irrelevancy magnified
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Interaction style -- GUI Question and answer
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Interaction style -- GUI Question and answer Design issues Need careful planning of dialog Avoid getting stuck in loops Don’t ask the same thing twice unless necessary Default is useful Nicely designed, good for novices
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Interaction style -- GUI Menus Various types Bars Block Button Full screen Pop-up, tear-off Cascade menus System dictates what can be input next Advantage Supportive: clear signal of what to input next Disadvantage Less flexible: amount of input limited Multiple selection can be cumbersome What if user want to select nothing?
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Interaction style -- GUI Menus Design decisions 7 2 rules: avoid too many items on menus Also make novice hard to choose Naming menus Unify menus if possible Board vs. Deep menus Ordering of menu items Frequency vs. Alphabetical vs. Categorical vs. Conventional
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Interaction style -- GUI Forms A predefined sequence User cannot move-on until all parts of form filled Auto-skip feature to move to the next input Advantage Supportive: very clear directives Disadvantage Non-flexible
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Interaction style -- GUI Forms Design issues Ordering/Division of requests “Next step” When to check for errors
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Issues in GUIs Use of metaphors Process: drag and drop mimics moving Symbols: icons represent objects/tasks E.g. of iconic interfaces Desktop Paintbox Spreadsheet
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Why icons Metaphor mimic reality – comfort for users Easy to learn Easy to retain knowledge Good feedback available
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Limitations Possibility of confusion Meaning of icons Meaning of action Selection vs Dragging Single-click vs. double-click Lack of flexibility
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Guideline in designing GUI for human need Need to concern about human responses Reaction time Movement time Attention Selective attention Focused attention Divided attention Sustained attention
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Reaction time Typically 200ms Longer if unexpected Longer for young and old Longer if periphery vision Movement time Movement speed varies for different directions/part of body
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Selective attention Monitoring multiple channels watch two windows Listen and watch Memory limitation 7 2 principle Stressful = less attention Design notes Need to be clear about importance of each channel Should avoid surprises (let user know what will likely to happen next) Channels should be close together
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Focused attention Attention to a single channel without distraction Typing on the WordPad while other things are happening Design guidelines Channel of interests should demand attention Competing channels should be far apart & distinct
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Divided attentions Attempting to do multiple things at once Design guidelines Tasks should be easy Allow prioritization
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