Human Computer Interaction

Week 4
Human-Computer Dialogue
Introduction
Dialogue
the process of communication
between two or more agents
Dialogue Style
the way users provide input
and systems present output
over time.
How to select a Dialogue Style
The users tasks
The users characteristics
The systems characteristics
The available input and
output devices
Dialogue Styles
Menu system in control
Form Fill-in
Direct Manipulation
Command Language
Natural Language user in control
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
Menu Advantages
Shortens Learning
Reduces keystrokes
Structures decision making
Appropriate for novice or intermittent
users
Easy to use
No need to remember many things
Menu Disadvantages
Danger of many menus
May slow frequent users
Consumes screen space
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
Form Fill-in
Users see a display of related fields,
move a cursor among the fields, and
enter data when desired
Form Fill-in
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 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
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
Direct Manipulation
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 Features (1)
Explicit action: the user points at and manipulates
objects on the screen
Immediate feedback: the results of the users 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 users
conceptual model of how the system should operate
and the display shows pictures of familiar objects
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
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
Command Language
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 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
Natural Language
Advantages
Relieves burden of
learning syntax
Disadvantages
Requires clarification
dialogue
May require more
keystrokes
May not show
context
Unpredictable
The systems responds to arbitrary natural
language sentences and phrases
Cognitive Issues in Direct
Manipulation
The Gulf of Execution
Refers to the distance between the users
goals and the means of achieving them
through the system.
The Gulf of Evaluation
Refers to the distance between the systems
behavior and the users goals.
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.
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.
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.