Post on 13-Mar-2016
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Human Computer Interaction
Week 4Human-Computer Dialogue
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Introduction
Dialogue the process of communication
between two or more agents Dialogue Style
the way users provide input and systems present output over time.
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How to select a Dialogue Style The users’ tasks The users’ characteristics The systems’ characteristics The available input and
output devices
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Dialogue Styles
Menu system in control
Form Fill-in Direct Manipulation Command Language Natural Languageuser in control
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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
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Menu Advantages Shortens Learning Reduces keystrokes Structures decision making Appropriate for novice or
intermittent users Easy to use No need to remember many things
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Menu Disadvantages Danger of many menus May slow frequent users Consumes screen space
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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
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Form Fill-in Users see a display of related
fields, move a cursor among the fields, and enter data when desired
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Form Fill-inAdvantages 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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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.
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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.
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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.
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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.
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Further Reading Preece, Chapter 13