ID
Conceptual Models
(Mental Models)
Summary
CSSE 477
October, 2011
From Ch 2 and Ch 8 of the ID book
See examples of user models at end!
Where you’re using these
•
In term project, next assignment –
1. Get user feedback to your prototype
2. Build / revise a mental model of users
3. From which you should develop a
conceptual model of your system
4. Then go for system implementation
User feedback
Mental model
of them
Conceptual model
Of the system
Build actual system
From big picture
User model
The user’s mental model of what’s happening
From problem space to design
space
• Having a good understanding of the
problem space can help inform the design
space
– e.g. what kind of interface, behavior,
functionality to provide
• But before deciding upon these it is
important to develop a conceptual model
Ch 2 Slide 7
The user’s mental model of what’s happening
Conceptual model
• Need to first think about how the system will
appear to users (i.e. how they will understand it)
• A conceptual model is a high level 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”
Ch 2 Slide 8
The user’s mental model of what’s happening
First steps in formulating a
conceptual model
• What will the users be doing when carrying out
their tasks?
• How will the system support these?
• What kind of interface metaphor, if any, will be
appropriate?
• What kinds of interaction modes and styles to
use?
Always keep in mind when making design decisions
how the user will understand the underlying
conceptual model
Ch 2 Slide 9
The user’s mental model of what’s happening
Conceptual models
• Many kinds and ways of classifying them
• Here we describe them in terms of core
activities and objects
• Also in terms of interface metaphors
Ch 2 Slide 10
The user’s mental model of what’s happening
Conceptual models based on
activities
• Giving instructions
– issuing commands using keyboard and function keys
and selecting options via menus
• Conversing
– interacting with the system as if having a
conversation
• Manipulating and navigating
– acting on objects and interacting with virtual objects
• Exploring and browsing
– finding out and learning things
Ch 2 Slide 11
The user’s mental model of what’s happening
Conceptual models based on
objects
• Usually based on an analogy with
something in the physical world
• Examples include books, tools, vehicles
• Classic: Star Interface
based on office
objects
Johnson et al (1989)
Ch 2 Slide 21
The user’s mental model of what’s happening
Which conceptual model is
best?
• Direct manipulation is good for ‘doing’ types of tasks,
e.g. designing, drawing, flying, driving, sizing windows
• Issuing instructions is good for repetitive tasks, e.g.
spell-checking, file management
• Having a conversation is good for children, computerphobic, disabled users and specialised applications (e.g.
phone services)
• Hybrid conceptual models are often employed, where
different ways of carrying out the same actions is
supported at the interface - but can take longer to learn
Ch 2 Slide 23
The user’s mental model of what’s happening
Interface metaphors
• Interface designed to be similar to a physical entity but
also has own properties
– e.g. desktop metaphor, web portals
• Can be based on activity, object or a combination of both
• Exploit user’s familiar knowledge, helping them to
understand ‘the unfamiliar’
• Conjures up the essence of the unfamiliar activity,
enabling users to leverage of this to understand more
aspects of the unfamiliar functionality
Ch 2 Slide 24
The user’s mental model of what’s happening
Benefits of interface metaphors
• Makes learning new systems easier
• Helps users understand the underlying
conceptual model
• Can be very innovative and enable the
realm of computers and their applications
to be made more accessible to a greater
diversity of users
Ch 2 Slide 25
The user’s mental model of what’s happening
Problems with interface metaphors
• Break conventional and cultural rules
– e.g. recycle bin placed on desktop
• Can constrain designers in the way they conceptualize a problem
space
• Conflict with design principles
• Forces users to only understand the system in terms of the
metaphor
• Designers can inadvertently use bad existing designs and transfer
the bad parts over
• Limits designers’ imagination in coming up with new conceptual
models
Ch 2 Slide 26
The user’s mental model of what’s happening
Conceptual models: from
interaction mode to style
• Interaction mode:
– what the user is doing when interacting with a system,
e.g. instructing, talking, browsing or other
• Interaction style:
– the kind of interface used to support the mode, e.g.
speech, menu-based, gesture
Ch 2 Slide 27
The user’s mental model of what’s happening
Many kinds of interaction styles
available…
•
•
•
•
•
•
•
•
•
•
Command
Speech
Data-entry
Form fill-in
Query
Graphical
Web
Pen
Augmented reality
Gesture
and even...
Ch 2 Slide 28
System model
The resulting conceptual model of your system
Conceptual design: from
requirements to design
•Transform user requirements/needs into a
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”
•Don’t move to a solution too quickly. Iterate,
iterate, iterate
•Consider alternatives: prototyping helps
Ch 8 Slide 16
The resulting conceptual model of your system
Three perspectives for a
conceptual model
•Which interaction mode?
How the user invokes actions
Activity-based: instructing, conversing,
manipulating and navigating, exploring and
browsing.
Object-based: structured around real-world
objects
Ch 8 Slide 17
The resulting conceptual model of your system
Three perspectives for a
conceptual model
•Which interaction paradigm?
desktop paradigm, with WIMP interface
(windows, icons, menus and pointers),
ubiquitous computing
pervasive computing
wearable computing
mobile devices and so on.
•Is there a suitable metaphor?
(contd)….
Ch 8 Slide 18
The resulting conceptual model of your system
Is there a suitable metaphor?
•Interface metaphors combine familiar
knowledge with new knowledge in a way that will
help the user understand the product.
•Three steps: understand functionality, identify
potential problem areas, generate metaphors
•Evaluate metaphors:
How much structure does it provide?
How much is relevant to the problem?
Is it easy to represent?
Will the audience understand it?
How extensible is it?
Ch 8 Slide 19
The resulting conceptual model of your system
Expanding the conceptual model
•What functions will the product perform?
What will the product do and what will the
human do (task allocation)?
•How are the functions related to each other?
sequential or parallel?
categorisations, e.g. all actions related to
telephone memory storage
•What information needs to be available?
What data is required to perform the task?
How is this data to be transformed by the
system?
Ch 8 Slide 20
The resulting conceptual model of your system
Using scenarios in conceptual
design
•Express proposed or imagined situations
•Used throughout design in various ways
scripts for user evaluation of
prototypes
concrete examples of tasks
as a means of co-operation across
professional boundaries
•Plus and minus scenarios to explore
extreme cases
Ch 8 Slide 21
The resulting conceptual model of your system
Using prototypes in
conceptual design
•Allow evaluation of emerging ideas
•Low-fidelity prototypes used early on,
high-fidelity prototypes used later
Ch 8 Slide 22
Examples of User Models
These are all taken from prior classes.
1.
2.
3.
4.
5.
For a drink recipe system
For a Music Library System
For a shared text editing system
For a customized spreadsheet system
For a Log File Parser System
The last one is the most complete, and follows the current
assignment!
Examples of User Models, cntd
1. For a drink recipe system:
• Because the testers are mostly college students, they will immediately
understand the problem space.
• I believe users of the system will easily figure out how to register, but may
be confused by the password rules. I also think they might try and search
for a recipe by ingredient instead of by name. I think that they will easily
figure out how to add a recipe to their favorites list, as long as they have
either a) A list of recipes displayed or b) a recipe selected. If they were to,
say, try to start from the main screen and add a recipe to favorites they may
be confused. I think users may ask what exactly a recipe is. I also think
that adding a recipe will be easily accomplished, and that editing a recipe
will be slightly more challenging, as they will have to re-find the recipe they
created. After this task has been performed once, replication will be trivial.
Users will find the clean interface refreshing.
• The interface is a bit like a search engine and a liquor cabinet.
Examples of User Models, cntd
2. For a Music Library System (Start of description)
• Users of the system will have three basic types, each with different usability
concerns:
• Requestors: These users will only have access to the song library and be
able to submit requests of the songs they are browsing.
– Understanding of problem space: Requestors will know what songs they want
and what the meaning of song terminology is. There is no assumption that they
have any specific familiarity with WMHD or this type of user interface.
– Usability Goals: Learnability and Effectiveness.
– Interface Metaphor: It’s kind of like the Rose class registration page. You can
browse listings and search based on criteria and select.
– Design Principles: Visibility and Feedback. The users can use feedback to use
the site without the need of instructions. They should be able to do things without
a lot of navigation to simply request a song.
– Interaction type: Exploring. Users browse the library.
•
More of this one – see notes, below!
Examples of User Models, cntd
3. For a shared text editing system (start of description)
• There is currently no system that allows multiple people to edit a document
in real-time on multiple computers. This makes peer-programming with
someone who is not in the same room very difficult. Current systems either
do not allow multiple users to edit the same document at the same time or
do not update all the documents in real time. And so it is important that our
project meets several usability goals. The system must be easy to learn so
that new users will not be hampered by using this system. The system also
must allow users to effectively perform text edits without a lot of extra
administrative work. It’s also important for the system to be efficient so that
edits to a document on one computer show up in real-time on other
computers in the session. The target users for our system are developers
who are coordinating work from potentially remote locations. Therefore, the
interface metaphor is a combination of an online instant messaging program
(like AOL Instant Messenger) and a text editor from an Integrated
Development Environment (like Visual Studio).
More of this one – see notes, below!
Examples of User Models, cntd
4. For a customized spreadsheet system
• We expect that people will be lost due to the
overwhelming amount of data which presented to them
within the program. Though we feel the data is very
cleanly organized and in good relationship to one
another, most typical users will not want to have to take
the time to look in depth into all the information. We
instead believe that users will want a way to view the
information in such a way that they can grep the data “at
a glance”. In order to do this, we have built in a graphing
feature which displays the data in a clean and very easy
to read chart (which is also highly customizable).
Examples of User Models, cntd
5. For a Log File Parser System (start of description)
• Problem Space Understanding
• The usability testers of the system should have a good idea of
the problem space. Although the specifics of the log files they
will be testing the system with are unknown, they have had
experience with going through log files and understand the
importance of being able to flag entries or write comments on
certain entries. If it were possible to get Northrop Grumman’s
engineers to be a part of our usability study, it would likely be
more fruitful than using people unfamiliar with the log files, but
that isn’t feasible for our usability study on such short notice.
• More of this one – see notes, below!