1. CHAPTER 2: Guidelines, Principles, and Theories
Designing the User Interface:
Strategies for Effective Human-Computer Interaction
Fifth Edition
Ben Shneiderman & Catherine Plaisant
in collaboration with Maxine S. Cohen and Steven M. Jacobs

2. Two dimensions to design rules
authority and generality
Standards – specific design rules
high authority and limited in application
Guidelines - low in authority and general

3. Principles – abstract design rules
high generality and low authority
More fundamental, widely applicable, and enduring than guidelines
Theories
Beyond the specifics of guidelines
Principles are used to develop theories

4. Standards Usually set by national & international bodies
ISO Standard 9241 Example

5. Guidelines Shared language Best practices Critics Proponents
Too specific, incomplete, hard to apply, and sometimes wrong
Proponents
Encapsulate experience

6. Navigating the interface
Sample of National Cancer Institute’s guidelines:
Standardize task sequences
Use thumbnails to preview large images
Ensure that embedded links are descriptive
Use unique and descriptive headings
Use check boxes for binary choices

7. Organizing the display
Smith and Mosier (1986) offer five high-level goals
Consistency of data display
Efficient information assimilation by the user
Minimal memory load on the user
Compatibility of data display with data entry
Flexibility for user control of data display

8. Principles
More fundamental, widely applicable, and enduring than guidelines
Need more clarification/interpretation
Fundamental principles
Determine user’s skill levels
Identify the tasks
Five primary interaction styles
Eight golden rules of interface design
Prevent errors
Automation and human control

9. Determine user’s skill levels
“Know thy user”
Design goals based on skill level
Novice or first-time users
Knowledgeable intermittent users
Expert frequent users
Multi-layer designs

10. Identify the tasks
Task Analysis usually involve long hours observing and interviewing users
Decomposition of high level tasks
Relative task frequencies

11. Interaction styles Direct Manipulation Menu selection Form fill-in
Command language
Natural language

12. Golden Rules (Heuristics)
Broad-brush design rules, may not be applicable in every case
Shneiderman’s Golden Rules of Interface Design
convenient and succinct
used in design, but can be used in evaluation
relate to abstract principles

13. Schneiderman’s 8 golden rules of interface design
Strive for consistency
Cater to universal usability
Offer informative feedback
Design dialogs to yield closure
Prevent errors
Permit easy reversal of actions
Support internal locus of control
Reduce short term memory load

14. Theories Beyond the specifics of guidelines
Principles are used to develop reliable, broadly useful theories
Theories – descriptive, explanatory prescriptive or predictive
Theories concern: motor, perceptual, or cognitive skills

15. More on theories Descriptive theories provide consistent terminology
Explanatory theories:
Observing behavior
Describing sequence of activities
Conceiving of designs
Comparing high-level concepts of designs
Prescriptive theories:
Giving designers clear guidance for choices
Predictive theories:
Enable designers to compare proposed designs for execution time or error rates

16. Perceptual, Cognitive, & Motor Skills
Perceptual or Cognitive subtasks theories
Predicting reading times for free text, lists, or formatted displays
Motor-task performance times theories:
Predicting keystroking or pointing times

17. Consistency
An important goal for designers is a consistent user interface.
Consistency for objects and actions/commands
Consistent use of color, layout, icons fonts, button sizes etc.
If terminology for objects and actions is orderly and describable by few rules, users will be able to learn and retain them easily.