Transcript Document 7304424

Conceptual
Model
Mr. John Kelleher
Conceptual Model
“
A description of the proposed
system in terms of a set of
integrated ideas and concepts
about what it should do, behave
and look like, that will be
understandable by the users in the
manner intended.
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Conceptual Models
“Run-Throughs”
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How many windows in your house?
Carelman’s Tandem “Convergent Bicycle (Model for Fiancés)
Carelman’s “Coffee Pot for Masochists”
Jacques Carelman, Catalog of Unfindable Objects, Balland.
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People form Conceptual
Models to:
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Predict future (or infer invisible) events.
Find causes for observed events.
Determine appropriate actions to cause desired changes.
Serve as mnemonic devices for remembering relations and
events.
Provide a means of understanding an analogous device.
Allow them to apply heuristic problem-solving strategies
designed to overcome information processing limitations.
However, often incomplete and vague
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Home thermostat
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Key aspects to design of a
conceptual model (1/2)
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Decide what user will be doing when carrying
out their tasks – his ‘interaction mode’
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searching for information? recording events?
E.g. Jeff Hawkin’s PDA (Palm Pilot)
E.g. Buchenau and Suri (2000) Defibrillator
E.g. Third Age Suit at ICE, Loughborough Univ.
This prompts the choice of interaction style
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E.g. PDA (pen interface), command line interface,
speech input, HUD (Head-Up Display)
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Key aspects to design of a
conceptual model (2/2)
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Actual concrete solutions thought through
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behavior of the interface
‘look and feel’
particular interaction styles
Content metaphors
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desktop
paper document
notebook with tabs
score sheet , stage with actors (Director)
accounting ledger (spreadsheet)
stereo (for all media players)
phone keypad
calculator
Web: "Shopping Carts"
Quicken: "CheckBook"
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Alternative Conceptual Models
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A better way?
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Types of Conceptual Models
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Structural model
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…explains what the system does independent of use
(it’s a system-centered model).
User has internalized structure of how the item works
Internalized declarative knowledge
Explanation of the underlying mechanism
Functional model
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…explains what the system does to assist a user’s
task (it’s a user-centered model)
Internalized procedural knowledge
Developed from past knowledge and experience in a
similar domain (calculator)
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Which model?
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Incomplete model
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Implications for HCI
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Users’ conceptual models are usually vague and
incomplete
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The Interface should match the understanding the
user already has
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just a piece of the puzzle
Contrast with earlier HCI advice, where the users’ must
grow the appropriate mental model of the application
Users prefer simple models
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simple and working solution (even it is not completely
correct)
Occam’s Razor
Threshold of Indignation
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Refrigerator
freezer
fresh food
Problem: freezer too cold, but fresh food just right
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Refrigerator Controls
Problem: freezer too cold,
but fresh food just right
What is your conceptual
model?
How do you adjust the controls?
Answer: keep the numerical setting
unchanged. Change the alphabetic
setting, C -> B
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Most Likely Conceptual Model
Freezer
Control
Freezer
Thermostat
Cold Air
Cooling
Unit
Fresh food
Control
Fresh
Food
Thermostat
Cold Air
Cooling
Unit
i.e., independent controls
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Correct Conceptual Model
Thermostat
(Location
Unknown)
Control A
Freezer
Valve
Cooling
Unit
Cold Air
Fresh
Food
Control B
Now can you fix the problem?
One control for two functions: Problem!
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How design is received
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Developers of systems construct their
mental models of how the system should
function. This is called the design model.
Users develop their own mental models of
how their tasks should be accomplished,
user’s model.
After contact with a system, users build
up a system image.
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Design Model & User’s Model
User’s Model
Design Model
System Image
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Users gets model from experience & usage
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through system image
What if design & user models don’t match?
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But designers often do not
intend that image
Designers and the majority of users have
never met.
“The user of the system starts off with goals
expressed in psychological terms. The
system, however, presents its current
state in physical terms”.
That’s how gulfs have been created. Thus
there is often a discrepancy.
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Three problems emerge
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2.
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Mapping problems - which controls the
temperature in the refrigerator and which
one for the freezer? not directly intuitive
Ease of control - it is often required to
manipulate several physical variables at
the same time for a simple user goal, like
maintaining total rate constant while
increasing the temperature.
Evaluation – requires prompt feedback
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Two Guidelines for Design
1. Provide a good conceptual model
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allows user to predict the effects of our actions
Problem:
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designer’s conceptual model communicated to user
through system image: appearance, written
instructions, system behaviour through interaction,
transfer, idioms and stereotypes
if system image does not make model clear and
consistent, user will develop wrong conceptual model
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Two Guidelines for Design (contd.)
2. Make things visible
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relations between user’s intentions, required actions,
and results are
 sensible
 non arbitrary
 meaningful
Visible affordances, mappings, and constraints
Use visible cultural idioms
Reminds person of what can be done and how to do it
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Good Design
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Scissors
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Affordances: holes for something to be inserted
Constraints: big hole for several fingers, small hole
for thumb
Mapping: between holes and fingers suggested and
constrained by appearance
Positive transfer and cultural idioms learned when
young constant mechanism
Conceptual model: implications clear of how the
operating parts work
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Bad Design
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12:00
Digital Watch
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Affordances: four push buttons to push, but not
clear what they will do
Constraints and mapping unknown: no visible
relation between buttons, possible actions and
end result
Transfer of training: little relation to analog
watches
Cultural idiom: somewhat standardized core
controls and functions but still highly variable
Conceptual model: must be taught
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Interface Metaphors
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Definition of Metaphor
 application of name or descriptive term to an object to which it is
not literally applicable
Purpose
 leverages our knowledge of familiar, concrete
objects/experiences to understand abstract computer and task
concepts
Metaphor is basic to human language for a similar reason: it
allows us to talk about knew or abstract things by drawing on
familiar experience:
 Time is like a line we move on
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We can go forward and look back
We can push a meeting back
Love is like a journey
(also like a fall)
A presentation tool
is like
a slide projector
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Metaphor
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Since functional models draw on past experience
and not everyone has computer experience, its
useful to draw on the real world.
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Hence the “desktop metaphor”:
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Directories are like folders
Files are like sheets of paper
Windows are like ?:
Menus are like menus
Deleting is like putting in the trash
Running an application program is like opening the doc.
Copy to buffer and restore is like cut-and-paste...
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Interface Metaphors
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Use metaphors that
matches user's
conceptual task
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desktop for office workers
paintbrush for artists
layers for animators
ledger for accountants
search engine for surfers
timeline for video editors
scrollbar, toolbar, portal
even Bluetooth!
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Uses of metaphors…
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as a way of conceptualising a particular interaction
style, e.g. using the system as a tool
as a conceptual model that is instantiated as part of
an interface, e.g., the desktop metaphor
as a way of describing computers, e.g., the Internet
highway
names for describing specific operations e.g., ‘cut’
and ‘paste’ commands for deleting and copying
objects
as a part of the training material aimed at helping
learning, e.g., comparing a word processor with a
typewriter.
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Opposition to interface
metaphors (1/3)
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Overly literal interpretation
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Break the rules
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Bin on desktop
Too constraining
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Unnecessary fidelity
Metaphors meant to support understanding of new domain
E.g. finding a deeply nested file or
moving a file to another folder
Conflicts with design principles
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Fidelity with metaphor compromises design principles
E.g. violating consistency principle with Mac bin
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Opposition to interface
metaphors (2/3)
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Not being able to understand the system
functionality beyond the metaphor
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Metaphor acts as straight-jacket to user’s vision
Overly literal translation
of existing bad designs
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Calculator (a) replicates
poor design elements
of ‘real’ calculators
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Opposition to interface
metaphors (3/3)
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Limits the designer’s imagination in conjuring
up new paradigms and models
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Always looking ‘backwards’
Microsoft Windows Media Player vs. WinAmp
Gentner & Nielsen (1996) Superbook
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Interaction Paradigms
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A particular
philosophy about
interaction design
Can inform novel
conceptual models
Beyond GUI
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Ubiquitous computing
Pervasive computing
Wearable computing
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Metaphors – Strengths &
Difficulties
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Strengths
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Gives a way for people to understand a new concept
quickly given what they know.
Helps to provide good choices for visual and audio
elements, as well as terminology.
Difficulties
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The metaphor may create expectations that are false along
with the true ones:
 Can I shred this file instead of putting in the trash can?
Our understanding is “functional” rather than “structural”.
That means understanding is relative to how we do things.
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Evaluating suggested metaphors
1. How much structure does the metaphor provide?
 Organises the disparate features
2. How much of the metaphor is relevant to the
problem? How inadequate is the metaphor?
3. Is the interface metaphor easy to represent?
4. Will your audience understand the metaphor?
5. How extensible is the metaphor?
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Consider these questions in light of a ‘shared calendar’
system.
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The Metaphor of Direct
Manipulation
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Direct Manipulation
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Central ideas
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the feeling of working directly on the task
An interface that behaves as though the interaction was
with a real-world object rather than with an abstract system
visibility of the objects of interest
rapid, reversible, incremental actions
manipulation by pointing and moving
immediate and continuous display of results
Almost always based on a metaphor
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mapped onto some facet of the real world task semantics)
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Object-Action vs Action-Object
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Select object, then do action
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interface emphasizes 'nouns' (visible objects) rather than
'verbs' (actions)
Advantages
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move
closer to real world
my.doc
modeless interaction
actions always within context of object
 inappropriate ones can be hidden
generic commands
 the same type of action can be performed on the object
 eg drag ‘n drop:
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Resources
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Chapter 2
Understanding and
conceptualising
interaction
Chapter 8
Prototyping and
Construction
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