Lesson 5

• The goal of Interaction design

  Designing for maximum usability
• General understanding

  Principles of usability
• Direction for Design

  Standards and Guidelines
• Capture and reuse design knowledge

  Design patterns
• Types of Design Rules:

  • Principles
  • Standards
  • Guidelines
• • Abstract design rules
  • Low Authority
  • High generality

  Principles
• • Specific design rules
  • High authority
  • Limited application

  Standards
• • Lower authority
  • More general application

  Guidelines
• Principles to Support usability:

  • Learnability
  • Flexibility
  • Robustness
• The ease with which new users can begin effective interaction and achieve maximal performance

  Learnability
• The multiplicity of ways the user and system exchange information

  Flexibility
• The level of support provided the user in determining successful achievement and assessment of goal-directed behavior

  Robustness
• Principles of learnability:

  • Predictability
  • Synthesizability
  • Familiarity
  • Generalizability
  • Consistency
• • Determining effect of future actions based on past interaction history
  • Operation visibility

  Predictability
• • Assessing the effect of past actions.
  • Immediate vs eventual honesty.

  Synthesizability
• • How prior knowledge applies to new system.
  • Guessability; affordance.

  Familiarity
• • Extending specific interaction knowledge to new situations

  Generalizability
• • Likeness in input/output behavior arising from similar situations or task objectives

  Consistency
• Principles of Flexibility:

  • Dialogue initiative
  • Multithreading
  • Task migratability
  • Substitutivity
  • Customizability
• • Freedom from system imposed constraints on input dialogue
  • System vs user pre-emptiveness

  Dialogue initiative
• • Ability of system to support user interaction for more than one task at a time.
  • Concurrent vs interleaving; multimodality.

  Multithreading
• • Passing responsibility for task execution between user and system

  Task Migratability
• • Allowing equivalent values of input and output to be substituted for each other.
  • Representation multiplicity; equal opportunity.

  Substitutivity
• • Modifiability of the user interface by user (adaptability) or system (adaptivity).

  Customizability
• Principles of Robustness:

  • Observability
  • Recoverability
  • Responsiveness
  • Task conformance
• • Ability of user to evaluate the internal state of the system from its perceivable representation.
  • Browsability; defaults; reachability; persistence; operation visibility

  Observability
• • Ability of user to take corrective action once an error has been recognized.
  • Reachability; forward/backward recovery; commensurate effort.

  Recoverability
• • How the user perceives the rate of communication with the system.
  • Stability

  Responsiveness
• • Degree to which system services support all of the user's tasks.
  • Task completeness; task adequacy.

  Task conformance
• • Suggest how to increase usability.
  • Differ in generality and authority.

  Design Rules
• Defines usability as effectiveness, efficiency and satisfaction with which users accomplish tasks.

  ISO 9241
• More suggestive and general.

  Guidelines
• Abstract guidelines applicable during early life cycle activities.

  Principles
• Detailed Guidelines applicable during later life cycle activities.

  Style Guides
• • "Broad brush" design rules.
  • Useful check list for good design.
  • Better design using these using nothing!

  Golden rules and heuristics
• Collections of Golden rules and Heuristics:

  • Nielsen's 10 Heuristics.
  • Shneiderman's 8 Golden Rules.
  • Norman's 7 Principles
• Shneiderman's 8 Golden rules:

  1. Strive for consistency
  2. Enable frequent users to use shortcuts
  3. Offer informative feedback
  4. Design dialogs to yield closure
  5. Offer error prevention and simple error handling
  6. Permit easy reversal of actions
  7. Support internal locus of control
  8. Reduce short-term memory load
• Norman's 7 Principles:

  1. Use both knowledge in the world and knowledge in the head
  2. Simplify the structure of tasks
  3. Make things visible: bridge the gulfs of Execution and Evaluation
  4. Get the mappings right
  5. Exploit the power of constraints, both natural and artificial
  6. Design for error
  7. When all else fails, standardize
• An approach to reusing knowledge about successful design solutions

  HCI design patterns
• Is an invariant solution to a recurrent problem within a specific context.

  Pattern