Mechanism Level Design - continued

1. Mechanism Level Design - continued Dialog boxes and fill-in forms Command language design Tightly-coupled windows (left over topic)

2. Dialog Boxes • Combination of menus, buttons • and fill-in techniques • Example: Find/Replace and Font Dialogs

3. Dialog Boxes: How they work Superimposed over the main window Engages the user in a “side” conversation offering information requesting input When user is finished viewing/changing information, accept or reject the changes and exit the dialog Dialog box disappears and user returns to main window

4. Fill-in Forms: How they work • An extreme case of a dialog box where most of the widgets are text entry fields • Or: the main window of a database or data entry application • Example: On-line shopping – page where shipping address and credit card details are provided • Many similar design issues, choices and guidelines

5. A MS Access Fill-in Form

6. Dialog Boxes: Overused? • Many designers use as primary interaction idiom • User must constantly bounce back and forth • Immediate and gross change to screen image is • visually distracting • Breaks the smooth flow of interaction between • the user and the program

7. Dialog Boxes: When they should be used • To concentrate information related to a single task or • object (such as printing) • To present infrequently used settings and functions • To control advanced or dangerous facilities • When a roomier setting is needed to present controls, making space for prompts and explanations

8. Dialog Boxes: Components Title Fields or other widgets Labels and prompts Terminating command(s)

9. Dialog Boxes: Types Bulletins – error, confirmation and information dialogs the most over-used Property dialogs (ex: font dialog) Function dialogs (ex: print dialog) Process/progress dialogs Also: modal v. modeless dialogs

10. Dialog Boxes: Design Guidelines • I. Reveal conceptual structure • Meaningful title • Logical grouping and sequencing of fields • Familiar field labels • Optional fields clearly marked • Explanatory messages for fields (prompts)

11. Dialog Boxes: Design Guidelines (cont.) • II. Orchestration guidelines: • Avoid overuse of modal dialogs • Display close to appropriate items • Avoid or minimize overlap • Should disappear if main app is closed

12. Dialog Boxes: Design Guidelines (cont.) • I. Offer consistent and clear affordances • Offer “OK” and “Cancel” on all modal dialogs (except bulletins) • Visually differentiate modeless dialogs from modal • Don’t put close box on modal dialogs (why??)

13. Dialog Boxes: Design Guidelines (cont.) • IV. Follow other usability heuristics • Visually appealing layout of the form • Visible space and boundaries for data-entry fields • Convenient cursor movement • Specify “tab order” in VB • Consistent terminology and abbreviations • Easy editing of characters and fields (now standard) • Error prevention • Use selection lists • Signal coding of phone numbers, dates, etc. • Error messages for unacceptable values • Comprehensible instructions

14. Dialog Boxes: Design Guidelines (cont.) • V. Internal Layout Guidelines • Visually distinct title • Top-left to bottom-right sequencing • Consistent layouts (margins, grid, white space, lines, boxes) • Consistent terminology, fonts, capitalization, justification • Standard buttons (OK, Cancel) • Error prevention by direct manipulation widgets

15. Design Choices for Text Entry Fields • Insert vs. overtype mode • Different forms of prompts: • Date: _____________ • (MM/DD/YY) • Date: _ _ / _ _ /_ _ _ _ (01 – 31 – 2004) • SS# _ _ _ - _ _ _ - _ _ _ _ • Size ___ (8, 10, 12, 14, or 16)

16. Design Choices for Text Entry Fields (cont.) • Validation options: • Accept any input • “Hot” validation – check each keystroke • “Cold” validation – when to perform it? • Validation feedback: • modal dialog, tooltip, color coding

17. Guidelines for Text Entry Fields • Visually distinguish text entry fields from text display fields • Always use insert mode (or always overtype mode) • Clue the user why validation has failed • Follow text display guidelines, such as: • Left-justify character fields, right justify numbers

18. Command Interfaces • Benefits: power/expressiveness, efficiency, match to task, • easy to customize for expert user • Issues: human comprehension, learnability, memorability • grep -v ^$ filea > fileb • Elements of commands: • Action • Objects • Options

19. Command Language Design Design Process Analyze functionality needed Task actions and objects Interface actions and objects (naming) Syntax for combining actions, objects, options Common Design Errors Excess functionality (too many objects and actions) Inconsistency due to uncoordinated design

20. Command Interface Design Guidelines • Make frequently-used actions easy to perform • Consistent terminology (naming and syntax for options) • Consistent argument/option ordering (positional consistency) • Meaningful names vs “codes” • Grammatical consistency (part of speech) • Keyword parameters

21. Command Language Structure Hierarchical design (consistent syntax) Position arm higher Move arm down Congruent design (meaningful opposites): Forward robot Robot back Congruent and hierarchical Move arm up Move arm down

22. Command Interface Design Guidelines (cont.) • Famous (Carroll, 1982) “paper” experiment for robot languages: • Hierarchical design • Congruent design • Subjects said they preferred non-hierarchical, congruent design. Performance was best for hierarchical, congruent design. • But on-line test might differ due to longer hierarchical commands.

23. Command Naming (lots of studies) • Guidelines: • Avoid computer jargon, use domain jargon • (Nielsen: speak the user’s language) • use specific v. general terms (Black and Moran famous experiment showed infrequent terms worked better.) • use distinct terms (avoid: sen, sea, sel) • use congruent pairs • use grammatical consistency

24. Command Abbreviations • Abbreviation strategies: • truncation delete  del • vowel drop move  mv • first-and-last quit  qt • first of each word send mail  sm • familiar (QTY, PCT) • Phonetic view  vu

25. Command Abbreviations (cont.) BS recommends rule-based approach with secondary rule for handling conflicts. Experiments show: truncation rule is easier to remember fixed length abbreviations may be better do not incorporate common word endings teach initially using full names, then learn abbrevs. Should not be used in error messages

26. Tightly-coupled windows • Used for: • Structured applications with linked data sets • Flexible browsing - overview and detail • Pop-up annotations/tool tips • Coordination techniques: • Synchronized scrolling Dependent-windows opening • Hierarchical browsing Dependent-windows closing • Direct selection Save or open window state • Two-dimensional browsing

27. Image Browsing and Tightly-coupled Windows Definition: show a graph, map or image in “over” view, with a field-of-view box that can be moved. Detailed view of the contents of the box appears in a linked window. Purpose: support display of large complex images (medical, geographic, design diagrams, etc.)

28. Image Browsing and Tightly-coupled windows(cont.) • Design issues: • zoom factor (between 5 and 30) • zoom factor/box size (fixed or flexible) • intermediate levels? (control of number of views) • single-view zooming, fisheye view • window placement (side by side most common) • image update (continuous v. at end of move) • coupling other interface widgets (sliders, etc.)

29. Image Browsing and Tightly-coupled windows(cont.) • Classification of Image-oriented tasks • Image generation • Open-ended exploration (“browsing”) • Diagnostic • Navigation • Monitoring