Design Principles
John C. Tang
September 13, 2007 NEEDS
DESIGN
EVALUATE IMPLEMENT

Today
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Updates on facebook project
Conceptual model
Feedback
Constraints
Affordances
Action cycle
– Gulf of execution
– Gulf of evaluation
Time for group work

facebook group project
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Discussion section topic, Sept. 19
– Introduction to facebook platform
– Basic familiarity with features, constraints of platform
Project ideas
– Yes! You need to do something different
– We know about the applications in lists
– Group design process  generate new idea
– Convince us why it is better than prior ideas

facebook group project
(2)
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Implementation effort should be realistic
Must demonstrate working prototype
– OK if not all aspects are working
User study must test for complete idea
– Hybrid working prototype, paper prototype
– Wizard of Oz

Great discussion sections!
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Really appreciated good work
All slides uploaded to the web site
Allowing extra time (until 5:00pm today) to form groups
Take advantage of office hours (Brian, me, Christine) for feedback on topic ideas
Stanford Big Face(book)-off?

Social networking
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Social networking fueled by
“exhibitionism”
– Social status
– Contests
– Popularity
Alternatives
– Collectivism
– Activism
?

FB: Causes
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Promote awareness of UN Millennium project goals
– Educate people about goals
– Award “badge” for passing quiz
– Community recognition for shared awareness

Criteria: Review facebook application (Due Sept. 18)
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Pick an interesting application
Clearly explain to us what it does (illustrated)
Observe at least 2 non CS160 people using application (give demographic info)
Write review
– What works well
– What doesn’t work well
– Support with evidence from observations
– Suggested improvements
– Shouldn’t be more than around 5 pages

Design nuts & bolts
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Identified need
Conducted Contextual Inquiry
Stimulated ideating skills
Exercised visualizing skills
Working towards getting pixels on screen

Conceptual model
View of the system as the user believes it to be, especially how the user can act upon it and what the system’s responses mean

Conceptual Model of a
System
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Design Model
– The model the designer has of how the system works
System Image
– How the system actually works
– The structure and behavior of the system
User’s Model
– How the user understands how the system works
The most important thing to design is the user’s model. Everything else should be subordinated to making that model clear, obvious, and substantial. That is almost exactly the opposite of how most software is designed . David Liddle

Raising the bar: self-evident design
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Back in 1946, users had to be highly trained to use ENIAC
– Researchers
– Military
– technicians

Today’s computer manual

Conceptual Model of a
System (augmented)
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Design Model
– The model the designer has of how the system works
System Image
– How the system actually works
– The structure and behavior of the system
User’s Model
– How the user understands how the system works
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Some “repair” between the designer and user
– User manual
– FAQ

A bad example
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Radiator control

A good conceptual model
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Allows users to reason through:
– What can I do?
– How do I do it?
– What result will it have?
– What is it telling me?

Conceptual Model and
Reality
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User’s conceptual model does not always have to match reality
– Must be consistent with system’s behavior, reactions

My new refrigerator
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Temperature controls for GE EnergyStar refrigerator
We know from Norman that this is probably not how refrigerators work
But it’s how we want to control temperature

Iterative revision of the conceptual model
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As user interacts, conceptual model is revised
– Breakdowns (unfulfilled expectations or unclear representations) require explicilty revising conceptual model
– Consistency is key for developing robust conceptual model

What’s your conceptual model
Read? Feedback? Archival? Contribute?
Email
IM
Wiki
Blog

Norman’s 7 stages of action
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User
Translating goals
To actions
Based on user’s model

Norman’s 7 stages of action
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System presents results back to user
According to design model

Gulfs of execution and evaluation
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Note:
We’re even assuming the computer works perfectly!

The Gulfs
Where thought is required
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Gulf of execution -- thinking required to figure out how to get something done -transforming high-level intention into specific physical actions
Gulf of evaluation -- thinking required to understand what is being perceived -transforming raw sensory data into an understanding of objects, properties and events

The gulfs simplified
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Gulf of execution
– How do I do it?
Gulf of evaluation
– What did it do?
evaluation execution

Example

Overcoming the gulfs
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Gulf of execution
– Make commands and mechanisms of the system match the thoughts and goals of the user
Gulf of evaluation
– Make output displays present a good conceptual model of the system that is readily perceived, interpreted, and evaluated

Design Principles
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Visibility
Natural mapping
Feedback
Affordances

Visibility
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Primary controls visible
Secondary controls discoverable

Three crucial “visibilities”
1.
2.
3.
Of objects of interest
Of available actions
Of system status (feedback)

Remote control (good)

Remote controls (bad)

Car radio
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Primary controls visible
But how do you set radio station preset?

iPod
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How do you scan forward?

Learned conventions
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De facto standards that become established over time

Natural mapping
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Naturally connecting user’s model with system model
– taking advantage of physical analogies and cultural standards
– Physical properties (stove burner layout)
– Metaphorical/linguistic (on is up)
– Analogous function (playback control buttons)
“Natural” is individual and culture-specific

Stovetop control

Natural mappings
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Minimize the number of cognitive steps to transform action into effect, or perception into comprehension.
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Applicable to both action and displays
(execution and evaluation).
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Minimize the need for labels, instructions, help systems.

Different contexts for
“natural”
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Social and organizational contexts
– Office work
– Off the desktop
– Out-of-doors
Cultural norms
– Red and green
– Reading direction
– What may be offensive

Conflicting mappings?

Feedback
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Timely communication of system status

Visibility of system status, feedback
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At all times, the system visually indicates what state it is in.
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Examples:
- Hourglass “wait” icon
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- Progress bars
- Security padlock on browser

Progressive vs. interruptive feedback
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Feedback can be progressive, a part of the sequence of actions themselves
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Feedback can also be interruptive, a break in the sequence of actions
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Smooth is usually preferred to interruptive

Multimodal feedback
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Visual
Aural
Tactile
Smell?

Affordances
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“...the perceived and actual properties of the thing, primarily those fundamental properties that determine just how the thing could possibly be used.” [Norman]

In other words
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How a thing appears tells us how the thing can be used.
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(Whether the implied use matches the intended use is a question for design.)

Example
Knurling provides a visual affordance for
“gripping.”

Example
I’m Clickable I'm Not Clickable

William Gaver, 1991
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“People perceive the environment directly in terms of its potentials for action.”
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“An affordance of an object … refers to attributes of both the object and the actor.”
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“…when the apparent affordances of an artifact matches its intended use, the artifact is easy to operate. When apparent affordances suggest different actions than those for which the object is designed, errors are common.”

Affordances and metaphors
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Metaphors meant to “jump start” user’s conceptual model for a system
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Affordances meant to “jump start” user’s conceptual model for interacting with an artifact
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As with metaphors, if affordances are designed poorly, they thwart developing a correct conceptual model

Perceptible affordance
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When there is perceptual information for an existing affordance.
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Knurling communicates that you can actually move and resize the window with it.

Hidden affordance
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When there is not perceptual information for an existing affordance.
This is actually a button.

False affordance
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When there is perceptual information for an affordance that does not exist .
OK

False affordance?

Sequential affordance
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Acting correctly on a perceptible affordance leads to information indicating new affordances

Perceived affordances
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Norman primarily concerned with perceived affordances - what the user understands the affordances to be
The correct parts must be visible and they must convey the correct message
If you can't see it (or find it) you can't use it
Perceived affordance is a combination of what you see, and what you know

Experts and novices

Novices
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Unfamiliar with the system
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Possibly unfamiliar with the context and domain
Often apprehensive about technology
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Often unwilling to explore interfaces for fear of inflicting permanent damage
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Confidence develops slowly at first

Experts
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Familiar with the system, context, and domain
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Usually comfortable with technology
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Willing to explore interfaces, try new things, teach themselves (Rely heavily on undo.)
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Confidence develops quickly

Usability curves for different system types
Intermediate Expert
Time
Novice
Time
Info Kiosk
Time Time

Designing for experts and novices
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Often difficult to design for both at once
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Experts require rapid control and feedback. The computer is interrupted more by them
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Novices require steady and comprehensible control and feedback.
They are interrupted more by the computer

Experts and Novices
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In direct manipulation interfaces:
- Provide menu accelerators, keyboard shortcuts
- Command lines within GUIs (e.g.,
Visual Studio)
- Reveal complexity over time
- Nest complexity in space
- Make first tier actions most apparent

Assignments
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First group assignments!
Project topic (Due Sept. 18)
– Team name (branding)
Contextual inquiry (Due Sept. 27)
– Pick appropriate method
– Group analysis
– Report

Project topic (due Sept.
18)
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1 pg. description of project area
– Need
– Conceptual approach
– Similar to “commercial” presentations
– Email addresses
Preferably due in class, but if you need more time, 5:00pm Tuesday
– Take advantage of office hours
Grading criteria: Just do it!

Contextual Inquiry (Due
Sept. 27)
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Pick appropriate method
– Direct observation
– Surveys
– Diary study
– ESM
Each team member must do at least one first-hand data collection!

Contextual Inquiry (Due
Sept. 27)
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Group analysis of data
Report
– Method used
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Participants
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Activity
– Analysis
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Resources used
Hindrances encountered
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Design implications for improvement
(Persona)

Contextual Inquiry:
Grading criteria
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Picking appropriate method
Conducting method properly
– What participants you pick
– Appropriate description of method
Analysis
– Including data from contextual inquiry
– Drawing appropriate conclusions
– Design implications

Extra slides (not presented in class)

Next time
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Readings
– Norman, DOET, Chapter 3
Assignments
– facebook application review
– Group project topic

Visibility (bad examples)
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Clear what to do, but is this the best way to enter Social Security number?
All the states are visible, but is this the most effective way to select state?

Overwhelming tabs
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Everything is discoverable, but way too much information