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Design Principles – Part 2 of 3

Design Principles – Part 2 of 3. Learnability Principles Flexibility Principles Last revised 9/2010. Learnability: Predictability. Determining effect of future actions based on past interaction history Operation visibility Can see avail actions menus vs. command shell

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Design Principles – Part 2 of 3

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  1. Design Principles – Part 2 of 3 Learnability Principles Flexibility Principles Last revised 9/2010

  2. Learnability: Predictability • Determining effect of future actions based on past interaction history • Operation visibility • Can see avail actions • menus vs.command shell • Grayed out menuitems UI Design - Georgia Tech

  3. Mental Models - Aid Predictability • Mental models are not always right • May be too superficial • Functional model • Stimulus - response • “Press the accelerator once, then turn the key” • At surface or superficial level • Structural model • Deeper sense of why it happens, not just what happens • “Press the accelerator to engage the automatic choke on a carburetor” • Do you have a perfect mental model of Microsoft Word? UI Design - Georgia Tech

  4. Learnability: Familiarity • Does UI task leverage existing real-world or domain knowledge? • Guessability • Familiar affordances • Use of metaphors • Potential pitfalls • Are there limitations on familiarity? UI Design - Georgia Tech

  5. Learnability: Consistency • Likeness in behavior between similar tasks/operations/situations/terminology • Interaction sequences • Quicken on Mac – Option-P prints check, not current document • Output • Dialogue box always has a close button • Screen layout • Menu items always in same place - leverage “muscle memory” • Is this always desirable for all systems, all users? UI Design - Georgia Tech

  6. Consistency (cont’d) • Avoid special cases and special rules • Supports generalization by user, avoids frustration • For command line systems - consistent syntax • Find consistency between commands, unify them - as in Unix pipes for file I/O and for process inter-communications UI Design - Georgia Tech

  7. (In)Consistency Example • For a graphics program that uses a CSO (Currently-Selected Object) • Create a new primitive, it becomes the CSO • Duplicate a primitive, the old primitive remains as CSO UI Design - Georgia Tech

  8. Drag a file icon to: Folder on same physical disk Folder on another physical disk Different disk Trash can Result: File is moved to folder File is copied there File is copied there File is discarded (In)Consistency Example - Macintosh UI Design - Georgia Tech

  9. FSM’s can Reveal Inconsistencies UI Design - Georgia Tech

  10. Flexibility: Dialog Initiative • Not hampering the user by placing constraints on how dialog is done • User drives - preferred • User initiates actions • More flexible, generally more desirable • System drives • System does all prompts, user responds • A strict sequence is needed • Sometimes necessary • Example – installing new software • Example - ??? UI Design - Georgia Tech

  11. Flexibility: Multithreading • Allowing user to perform more than one task at a time • A big complaint about iPhone and iPad • Windows and Mac OS support UI Design - Georgia Tech

  12. Flexibility: Task Migratability • Ability to move performance of task to the entity (user or system) that can do it better • Dynamic ‘function allocatoin’ • For what kinds of tasks should the user be in control? • What happens if system does things the user is not expecting? • First time a word-processor did auto formatting? • Example - Spell-checking • DWIM – Do What I Mean UI Design - Georgia Tech

  13. Example – PPt Spell Check UI Design - Georgia Tech

  14. Flexibility: Substitutivity • Flexibility in how actions are specified • Allow user to choose suitable interaction methods; accelerators • Allow different ways to • perform actions, specify data, configure • Allow different ways of presenting output • to suit task& user UI Design - Georgia Tech

  15. Flexibility: Substitutivity • Drafting & page layout systems • Indicate positions with cursor or • By typing in coordinates • Point at spreadsheet cell vs enter name • Give temperature via slider or by typing • Other examples??? UI Design - Georgia Tech

  16. Flexibility: Customizability • Ability of user to modify interface • By user - adaptability • Is this a good thing? • By system - adaptivity • Is this a good thing? UI Design - Georgia Tech

  17. Customizing Toolbars in Powerpoint • Pros and cons of using? UI Design - Georgia Tech

  18. End Part 2 of 3 UI Design - Georgia Tech

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