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COMP 3715 Spring 05

COMP 3715 Spring 05. 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. Interface design principles. Naturalness Consistency

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COMP 3715 Spring 05

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  1. COMP 3715 Spring 05

  2. 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

  3. Interface design principles • Naturalness • Consistency • Relevance • Supportiveness • Flexibility

  4. 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

  5. Consistency • Input format • Output format • Menu layout • Messages • No surprises!

  6. Relevance • No redundancy • Minimize required input • Key strokes • Minimize required information • Minimize output messages • Unnecessary information • Irrelevant information scare users

  7. Supportiveness • Need adequate information to user • Enough feedback to user • Need to determine the user’s need • Novice vs. Expert

  8. 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

  9. 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

  10. 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

  11. Interaction style • Graphical user interface • Question and answer • Menu • Form

  12. 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

  13. Interaction style -- GUI • Question and answer

  14. 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

  15. 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?

  16. 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

  17. 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

  18. Interaction style -- GUI • Forms • Design issues • Ordering/Division of requests • “Next step” • When to check for errors

  19. 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

  20. Why icons • Metaphor mimic reality – comfort for users • Easy to learn • Easy to retain knowledge • Good feedback available

  21. Limitations • Possibility of confusion • Meaning of icons • Meaning of action • Selection vs Dragging • Single-click vs. double-click • Lack of flexibility

  22. 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

  23. 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

  24. 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

  25. 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

  26. Divided attentions • Attempting to do multiple things at once • Design guidelines • Tasks should be easy • Allow prioritization

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