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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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How many windows in your house?
Conceptual Models “Run-Throughs”
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:
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
Home thermostat
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Key aspects to design of a conceptual model (1/2) Decide what user will be doing when carrying
out their tasks – his ‘interaction mode’ 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 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) Actual concrete solutions thought through
behavior of the interface ‘look and feel’ particular interaction styles
Content metaphors 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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Types of Conceptual Models
Structural model …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 …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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Implications for HCI Users’ conceptual models are usually vague and
incomplete just a piece of the puzzle
The Interface should match the understanding the user already has Contrast with earlier HCI advice, where the users’ must
grow the appropriate mental model of the application Users prefer simple models
simple and working solution (even it is not completely correct)
Occam’s Razor Threshold of Indignation
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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
i.e., independent controls
Freezer
Thermostat
FreezerControl
CoolingUnit
FreshFood
Thermostat
Fresh foodControl
CoolingUnit
Cold Air
Cold Air
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Correct Conceptual Model
Now can you fix the problem?One control for two functions: Problem!
Thermostat(Location Unknown)
Control A
Freezer
CoolingUnit
FreshFood Control B
Cold Air
Valve
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How design is received
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
Users gets model from experience & usage through system image
What if design & user models don’t match?
Design ModelUser’s Model
System Image
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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
1. Mapping problems - which controls the temperature in the refrigerator and which one for the freezer? not directly intuitive
2. 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.
3. Evaluation – requires prompt feedback
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Two Guidelines for Design1. Provide a good conceptual model
allows user to predict the effects of our actions
Problem: 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 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
Scissors 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 Digital Watch
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
12:00
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Interface Metaphors 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
We can go forward and look back We can push a meeting back
Love is like a journey(also like a fall)
A presentation toolis like
a slide projector
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Metaphor Since functional models draw on past experience
and not everyone has computer experience, its useful to draw on the real world.
Hence the “desktop metaphor”: 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
Use metaphors that matches user's conceptual task
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… 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) Overly literal interpretation
Unnecessary fidelity Metaphors meant to support under-
standing of new domain Break the rules
Bin on desktop Too constraining
E.g. finding a deeply nested file or moving a file to another folder
Conflicts with design principles Fidelity with metaphor compromises design principles E.g. violating consistency principle with Mac bin
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Opposition to interface metaphors (2/3)
Not being able to understand the system functionality beyond the metaphor Metaphor acts as straight-jacket to user’s vision
Overly literal translation of existing bad designs Calculator (a) replicates
poor design elements of ‘real’ calculators
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Opposition to interface metaphors (3/3)
Limits the designer’s imagination in conjuring up new paradigms and models Always looking ‘backwards’ Microsoft Windows Media Player vs. WinAmp Gentner & Nielsen (1996) Superbook
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Interaction Paradigms
A particular philosophy about interaction design
Can inform novel conceptual models
Beyond GUI Ubiquitous computing Pervasive computing Wearable computing
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Metaphors – Strengths & Difficulties
Strengths 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 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? Consider these questions in light of a ‘shared calendar’
system.
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The Metaphor of Direct Manipulation Direct Manipulation
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 Central ideas
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 mapped onto some facet of the real world task semantics)
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Object-Action vs Action-Object
Select object, then do action interface emphasizes 'nouns' (visible objects) rather than
'verbs' (actions) Advantages
closer to real world 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:
my.doc
move