1. EPFL, spring 2011 - week 8!
conceptual design

2. objectives of this lecture
➝ know the different types of
models which are
relevant to the HCI design process.
➝ understand how
➝ models influence users interaction with the system
➝ conceptual design aims to exploit this.
➝ appreciate
problems with applying conceptual
design approach.
This lecture is based on a conceptual design lecture by Angela Sasse (UCL)

3. conceptual design idea

4. models, models & more muddles
➝ user s model/mental model
➝ design model/conceptual model
➝ system image
➝ user model
➝ metaphor
➝ analogy

5. user s model
➝ internalised model of system held by user, formed
as a result of interaction with the system
➝ can also be result of directed training
➝ origins: mental models research in cognitive
psychology and instruction
➝ Wason-task
A K Car Train
2 7 Sheffield Manchester

6. design model
➝ representation of system which is
➝ accurate, complete,consistent !
➝ held by
➝ designer of system, expert users, trainers
➝ should be based on users
➝ task
➝ previousknowledge and experience
➝ perceptual and cognitive limitations

7. system image
➝ everything the user sees of the system or interacts
with:
➝ user interface (incl. help)
➝ documentation
➝ training / marketing
User Manuals
Screen
HELP! display
Training

8. Tog on conceptual design
“Users will add to what is so clearly
communicated on the display every past
experience that they have had, relevant or
not. If the interface carries any trace of
ambiguity, the user will find it out and
jump to the wrong conclusion. In short,
the user will insist on doing everything
wrong, wrong, wrong!”
(Tognazzini 1992)

9. problems
➝ How to convert/integrate output of TA into a design
model.
➝ How to identify users’ existing knowledge and
experience which provides a basis for a design
model.
➝ How to communicate a chosen design model through
the user interface in a manner which supports the
construction of an appropriate
users’ model.
Sasse (1997)

10. how useful are user s models?
➝ users will construct models, whether the designer
aims for this or not
➝ trying to direct model-building process is
worthwhile - but needs to be checked*
➝ can try to cue/exploit existing models (user tasks,
related systems)
➝ it is often suggested that metaphors can be used
for this purpose ...

11. the lure of metaphors
"The desktop metaphor ... is an inviting
metaphor that provides easy access to the
system. Once users are emerged in the !
desktop metaphor, users can adapt readily
to loose connections with physical situations -
the metaphor need not to be taken to its logical
!
extremes."
!
(Apple Human Interface Guidelines, 1987)
!
But !
  !

12. metaphor
➝ existing model from a different domain which
has similar structure to intended user s model
➝ exploit user s existing knowledge and
experience to construct appropriate user s
model
➝ facilitate access and encourage exploration

13. metaphor evaluation heuristics
Erikson in Baecker (1995) book gives a list of
heuristics for evaluating metaphors:
➝ 1. how much structure does metaphor provide?
➝ 2. how much of the structure is relevant to
problem?
➝ 3. is the metaphor easy to represent?
➝ 4. will intended users understand the metaphor?
➝ 5. can it be extended?

14. evaluating metaphors
Those features provided Those features provided by
by the system and the system and not
supported by the supported by the metaphor
metaphor (S+M+) (S+M-)
Features implied by the Features not implied by the
metaphor but not metaphor and not
supported by the system supported by the system
(S-M+) (S-M-)
conceptual
baggage

15. evaluating metaphors
conceptual baggage

16. implementing metaphors
➝ maintain compatibility with regard to:
➝ structure
➝ visualclues
➝ language
➝ pay special attention to:
➝ conceptual baggage
➝ functionality which exceeds metaphor

17. example: burglar alarm
➝ problem
➝ alarmstoo difficult to use; users don’t arm them
➝ occupied buildings are strongest deterrent
➝ analogy - car central locking
➝ design model: central locking plus home
aware
➝ system image
➝ simple: how to alarm
➝ friendly (non-technical)

18. evaluating users’ models (UCs)
➝ problem: user performance cannot be taken as
reliable indicator of user’s models
➝ important to elicit user’s models, but
➝ paper-and-pencil tests are not a good predictor of
hands-on performance
➝ verbalising changes thought process
➝ best: interactive methods
➝ constructive interaction
➝ teach-back

19. carrying out conceptual design
➝ conceptual design process is an idea; not much
tool support
➝ suitable methods around, but need to be
integrated in conceptual design process
➝ build up a repository of tools which can be used in
each of the conceptual design stages
➝ Conceptual Designer’s Toolbox

20. conceptual design toolbox (1)
1. eliciting users’ model of task
➝ task analysis
2. eliciting users’ relevant knowledge and experience
➝ scenarios
➝ contemporary legends
➝ help
desks
➝ FAQs
3. metaphor evaluation
➝ Anderson et al. framework

21. conceptual design toolbox (2)
4. constructing design model
➝ extend or merge metaphors or analogies
➝ structural model (as opposed to procedural model)
➝ creative design methods
5. implementing design model in system image
➝ linguistic,
structural and visual consistency
➝ interviews, scenarios, conceptual maps
➝ grounded theory (ID concepts, relationships, structures)
6. Evaluation
➝ verbalprotocols
➝ drawings
➝ constructive interaction, teach back

22. summary points
➝ users form internal representations of (mental models) of
systems they interact with.
➝ an appropriate model facilitates user system interaction, an
inappropriate one is likely to impair it.
➝ models can be communicated through UI (appearance and
behaviour) and training, but fit with users existing
knowledge and experience is crucial.
➝ metaphors can be used as basis of design model.

23. literature
Anderson, B., Smyth, M., Knott, R., Bergan, J., Alty, J. (1994): Minimising
Conceptual Baggage: Making choices about metaphor. In G. Cockton, S. Draper
& G. Weir: People and Computers IX -Proceedings of HCI 94, Glasgow, pp
179-194.
Gentner, S. & Stevens, A. L. [Eds.] (1983): Mental Models. Hillsdale, NJ: Erlbaum.
Johnson-Laird, P. N. (1983): Mental Models. Cambridge: Cambridge University
Press.
Nielsen, J. (1990): A Meta-Model for Interacting with Computers. Interacting with
Computers,2, 147-160.
Norman, D.A. (1986). Cognitive Engineering. In Norman & Draper [Eds.] User-
Centered System Design, 1986, Hillsdale, NY: LEA.
Norman, D. A. & Draper, S. W. [Eds.] (1986): User-Centered System Design.
Hillsdale, NY: LEA.
Robert, D., Berry, D., Mullaly, J. Isensee, S. (1998): Designing for the User with
OVID: Bridging User Interface Desing and Software Engineering. Macmillan
Technical Pub.
Tognazzini, B. (1992): Tog on Interface. Reading, Mass.: Addison-Wesley.