1. Chapter 9: Design Guidance and Design Rationale Kevin Juang David Bate Will Rodes

2. Topics  Sources of Design Guidance Standards Guidelines Style guides  Design Principles Simplicity Structure Consistency Tolerance  Accessibility  Design Rationale

3. Design Guidance  User Interface Standard A set of internationally agreed design principles or approaches Most common is ISO 9241  Ergonomic requirements for office work with visual display terminals (VDTs) Situations to use  Detailed starting point for development  Publicize its use  Client requires it

4. Design Guidance  Design Guideline Suggestion that is in between design principle and design rule in terms of detail

5. Design Guidance  Style Guides Collection of design rules and guidelines Commercial or customized Situations to use  Applied starting point for development  Target users already familiar  Associate with certain products

6. Design Principles  Simplicity Keep the interface natural to the users Break down complex tasks into subtasks

7. Design Principles  Structure Group related features Use metaphors

8. Design Principles  Consistency Leverage user’s mental model to aid learning and satisfaction Can enforce using style guides or GUI code reuse

9. Design Principles  Tolerance Use constraints Provide helpful error messages Emphasize recoverability  Forward error recovery  Backward error recovery

10. Accessibility  The Principles of Universal Design  W3C Web Content Accessibility Guidelines  Section 508

11. Design Rationale  Record Design decisions Reasoning behind those decisions  Format Table sorted by date Brief text with illustrations when appropriate  Advantages Record design thoughts for future reference Communicate design decisions to others Aids technical support and marketing

12. Questions?