Human-computer interaction:
users, tasks & designs
User modelling in user-centred system
design (UCSD)
Use with Human Computer Interaction
by Serengul Smith-Atakan ISBN 1-84480-454-4
© 2006 Middlesex University Press
By the end of this lecture you
should...
• Understand what ‘guidelines’ are, and why they are
important
– Be able to distinguish between ‘principles’, ‘design
rules’ and ‘standards’
– Where they come from
– Where and when to use them
• Be familiar with several important design principles
Use with Human Computer Interaction
by Serengul Smith-Atakan ISBN 1-84480-454-4
© 2006 Middlesex University Press
By the end of this lecture you
should...
• Describe various ways of creating user models
• Be aware of Nielsen’s heuristics and how they can
be used to evaluate interactive systems
Use with Human Computer Interaction
by Serengul Smith-Atakan ISBN 1-84480-454-4
© 2006 Middlesex University Press
Types of user model
•
•
•
•
•
Psychological theories as user models
Task analysis for user models
Cut-down psychological theories as user models
Simplistic psychological theories as user models
Simplex One as a simplistic theory
Use with Human Computer Interaction
by Serengul Smith-Atakan ISBN 1-84480-454-4
© 2006 Middlesex University Press
User models and evaluation
• Using design principles or heuristics for evaluation
• Evaluating user requirements with Simplex One
• Evaluating design options with Simplex One
Use with Human Computer Interaction
by Serengul Smith-Atakan ISBN 1-84480-454-4
© 2006 Middlesex University Press
Simplex One
A key feature of this model is that each cognitive module can take
input from any other module in the system via the executive
function.
Use with Human Computer Interaction
by Serengul Smith-Atakan ISBN 1-84480-454-4
© 2006 Middlesex University Press
Evaluating design options with
Simplex
1. Sensory and Perceptual Zone
Does the system provide adequate visual, auditory or other modality
input to people using it?
Are the immediate sensory memory requirements of the system too
much?
2. Output Zone
Does the system require reasonable responses from users?
Does the system provide adequate response support?
3. Abstract Working Zone
Does the system place too many demands on working memory?
Do the people who use the system have the necessary working
memory capabilities?
Use with Human Computer Interaction
by Serengul Smith-Atakan ISBN 1-84480-454-4
© 2006 Middlesex University Press
Evaluating design options with
Simplex
4. Long Term Data Warehouse
Does the system require the long term memory to hold too much
information?
Does the system support long term learning when necessary?
Do the people who use this system have the necessary memory
skills?
5. Executive Functions Zone
Does the design require too many or too complex operations?
Does the design require a level of task coordination which is too
detailed to learn easily?
Does the design make it very difficult to track and monitor current
progress in tasks?
Use with Human Computer Interaction
by Serengul Smith-Atakan ISBN 1-84480-454-4
© 2006 Middlesex University Press
Guidelines...
Guidelines
Principles
Design rules
Standards
Use with Human Computer Interaction
by Serengul Smith-Atakan ISBN 1-84480-454-4
© 2006 Middlesex University Press
Principles vs design rules
• A principle is a high level and widely applicable
guideline
• Design rules are principles that have been interpreted
for a particular design. They are narrow, focused,
practical and specific
Use with Human Computer Interaction
by Serengul Smith-Atakan ISBN 1-84480-454-4
© 2006 Middlesex University Press
Examples...
• Principles
– Know the user population
– Reduce cognitive load
– Engineer for errors
– Maintain consistency and clarity
• Design rules
– always position the waste bin in the bottom right
hand corner
– always issue a warning before the user deletes a file
Use with Human Computer Interaction
by Serengul Smith-Atakan ISBN 1-84480-454-4
© 2006 Middlesex University Press
Design rule or principle?
• How many ways can a guideline be interpreted?
– ‘always position the waste bin in the bottom right
hand corner’
– can only be interpreted one way, therefore design
rule
– ‘be consistent’
– can be interpreted lots of ways, therefore principle
Use with Human Computer Interaction
by Serengul Smith-Atakan ISBN 1-84480-454-4
© 2006 Middlesex University Press
Principles become design rules
• Principles and design rules are not entirely
separable things
• There should be a path from a principle to a design
rule
• In other words:
– Principles are intended to be general
– When they are interpreted for a specific design
they become design rules
Use with Human Computer Interaction
by Serengul Smith-Atakan ISBN 1-84480-454-4
© 2006 Middlesex University Press
A continuum...
Principles
Design rules
General
Widely applicable
‘Theoretical’
Specific
Narrow application
Practical
Use with Human Computer Interaction
by Serengul Smith-Atakan ISBN 1-84480-454-4
© 2006 Middlesex University Press
Standards
• A standard is a guideline with a high level of
authority
• Typically standards must be applied to a design
• Standards may be ‘in house’
• Standards may legally enforced
Use with Human Computer Interaction
by Serengul Smith-Atakan ISBN 1-84480-454-4
© 2006 Middlesex University Press
Standards
• It has to be definite when (or not) a standard has
been applied
• Therefore a standard tends to be a design guideline
• It is difficult to enforce something if it has multiple
interpretations
– (Unless you want to make lots of money for
lawyers)
Use with Human Computer Interaction
by Serengul Smith-Atakan ISBN 1-84480-454-4
© 2006 Middlesex University Press
Where do guidelines come from
• Practical experience
– Nielsen’s guidelines are based on his practical
experience in designing interactive systems
• Psychological theory
– Theories of how people behave inform ideas
about how to design usable systems
Use with Human Computer Interaction
by Serengul Smith-Atakan ISBN 1-84480-454-4
© 2006 Middlesex University Press
Well-known design principles
Well-known design principles
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•
Learnability
Flexibility
Predictability
Consistency
Recoverability
Responsiveness
Use with Human Computer Interaction
by Serengul Smith-Atakan ISBN 1-84480-454-4
© 2006 Middlesex University Press
Nielsen’s heuristics
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•
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Visibility of system status
Match between system and the real world
User control and freedom
Consistency and standards
Error prevention
Recognition rather than recall
Flexibility and efficiency of use
Aesthetic and minimalist design
Help users recognise, diagnose, and recover from
errors
• Help and documentation
Use with Human Computer Interaction
by Serengul Smith-Atakan ISBN 1-84480-454-4
© 2006 Middlesex University Press
Summary
• Guidelines characterise aspects of “good design”
• Can be used to aid design process
• Come in different forms
– Guidelines, Principles, Rules, Standards
– Vary in generality and authority
– require different degrees of interpretation
Use with Human Computer Interaction
by Serengul Smith-Atakan ISBN 1-84480-454-4
© 2006 Middlesex University Press
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User Modeling In User-Centered System Design (UCSD)