Human Computer Interaction

1. Human Computer Interaction Week 4 Human-Computer Dialogue

2. Introduction • Dialogue • the process of communication between two or more agents • Dialogue Style • the way users provide input and systems present output over time.

3. How to select a Dialogue Style • The users’ tasks • The users’ characteristics • The systems’ characteristics • The available input and output devices

4. Dialogue Styles • Menu system in control • Form Fill-in • Direct Manipulation • Command Language • Natural Language user in control

5. Menu • The users read a list of items, selected the most appropriate for their tasks, apply the syntax to indicate their selection, confirm the choice, initiate the action, and observe the effect • Examples: • Pull Down Menu • Pop Up Menu

6. Menu Advantages • Shortens Learning • Reduces keystrokes • Structures decision making • Appropriate for novice or intermittent users • Easy to use • No need to remember many things

7. Menu Disadvantages • Danger of many menus • May slow frequent users • Consumes screen space

8. Menu Design Guidelines • Make meaningful groupings • Make meaning sequences of items in a menu • Items should be brief and consistent • Permit type-ahead, jump-ahead, or other short-cuts • Permit jumps to previous menu • Use consistent layout and terminology • Help facilities • Kieger (1984) suggested: 4-8 items, 3-4 levels

9. Form Fill-in • Users see a display of related fields, move a cursor among the fields, and enter data when desired

10. Advantages Simplifies data entry requires modest training Assistance is convenient Permits use of form management tools Appropriate for knowledgeable intermittent users or frequent users Disadvantages Consumes screen space Often assume errorless performance Form Fill-in

11. Form Fill-in Guidelines • Meaningful Title / Prompt • Comprehensive instructions • Logical grouping and sequencing of fields • Visual appealing layout • Consistent terminologies & abbreviations • Error correction for characters and fields • Visual templates for common fields • Help facilities

12. Direct Manipulation • First coined by Shneiderman (1987) to refer to interfaces which include windows, icons, menus, and pointers (WIMP interface) • The users interact directly with the object of interest on a graphics screen while the system provides rapid feedback to the users

13. Advantages Visually present task concept Easy to learn Easy to retain Errors can be avoided Encourage exploration High subjective satisfaction Disadvantages May be hard to program Require graphics display and pointing devices Power user constrained Icon: semantic mapping Direct Manipulation

14. Direct Manipulation Features (1) • Explicit action: the user points at and manipulates objects on the screen • Immediate feedback: the results of the user’s action are immediately visible (e.g. selecting an icon) • Incremental effect: user action have an analogue / sequential dimension (e.g. dragging an icon) • Intuitive interaction: interaction matches the user’s conceptual model of how the system should operate and the display shows pictures of familiar objects

15. Direct Manipulation Features (2) • Learning by onion peeling: the complexity of the system is gradually revealed in layers as the user explores system facilities • Reversible action: all actions can be undone by reversing the sequence of manipulations • Pre-validation: only valid interactions have an effect, so that if the user points at an object and this makes no sense in terms of the current task, nothing happens on the display

16. Command Language • Command language originate with operating systems • Users issue a command and wait for the system to respond • If the result is correct, the next command is issued • If not, corrective action will be taken by the users

17. Advantages Flexibility Appeals to “power” users Support for user initiative Convenient for creating over defined macros Disadvantages Poor error handling Requires substantial training and memorization Command Language

18. Command Language Guidelines • Create explicit model of objects or actions • Choose meaningful, specific, distinctive names • Try for hierarchical structure • Prove consistent structure • Support for consistent abbreviation rules • Offer infrequent users the capacity to create macros • Consider command menu on high-speed displays • Limit number of commands and ways to accomplishing a task

19. Advantages Relieves burden of learning syntax Disadvantages Requires clarification dialogue May require more keystrokes May not show context Unpredictable Natural Language The systems responds to arbitrary natural language sentences and phrases

20. Cognitive Issues in Direct Manipulation • The Gulf of Execution • Refers to the distance between the user’s goals and the means of achieving them through the system. • The Gulf of Evaluation • Refers to the distance between the system’s behavior and the user’s goals.

21. Bridging the gulfs • The users can bridge the gulf of execution through changing the way they currently think and carry out the task toward the way the system requires it to be done. • The designers can bridge the gulf of execution by designing the input characteristics to match the users’ psychological capabilities. • The users can bridge the gulf of evaluation by changing their interpretation of the system image and evaluating it with respect to their goals. • The designers can bridge the gulf of evaluation by changing the output characteristics of the system.

22. Expanding the notion of directness • Semantic directness concerns the relationship between what the user wants to express and the meaning of the expressions available at the interface. • Articulatory directness concerns the relation between the meanings of expressions and their physical form.

23. The Primary Design Principles • Affordances • Perceptual, Sequential, and Sound. • Constrains • Physical, Semantic, Cultural, and Logical. • Mappings • Good Mappings: appear natural and intuitive to the users. • Feedback • Sending back to the user information about what action has actually been done and what result has been accomplished.

24. Further Reading • Preece, Chapter 13