EPFL, spring 2011 - week 8!conceptual design

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)

conceptual design idea

models, models & more muddles

➝  user’s model/mental model ➝ design model/conceptual model ➝  system image ➝  user model ➝ metaphor ➝  analogy

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

7 2

A K

Sheffield

Car

Manchester

Train

design model

➝  representation of system which is ➝ accurate, complete,consistent !

➝  held by ➝ designer of system, expert users, trainers

➝  should be based on users’ ➝  task ➝ previous knowledge and experience ➝ perceptual and cognitive limitations

system image

➝  everything the user sees of the system or interacts with: ➝ user interface (incl. help) ➝ documentation ➝  training / marketing

Training

User Manuals

Screen display HELP!

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)

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)

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 ...

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 !

!!!!!

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

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?

evaluating metaphors

Those features provided by the system and supported by the metaphor (S+M+)

Those features provided by the system and not supported by the metaphor (S+M-)

Features implied by the metaphor but not supported by the system (S-M+)

Features not implied by the metaphor and not supported by the system (S-M-)

conceptual baggage

evaluating metaphors

conceptual baggage

implementing metaphors

➝ maintain compatibility with regard to: ➝ structure ➝ visual clues ➝  language

➝ pay special attention to: ➝ conceptual baggage ➝  functionality which exceeds metaphor

example: burglar alarm

➝ problem ➝ alarms too 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)

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

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

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

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 ➝ verbal protocols ➝ drawings ➝ constructive interaction, teach back

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.

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.