This document discusses design rules and usability inspections for evaluating user interfaces. It begins by outlining principles, standards, and guidelines that provide direction for design. These include learnability, flexibility, and robustness. Common inspection methods are then described, such as heuristic evaluation where usability experts judge compliance with principles. Heuristic evaluation involves experts inspecting independently then debriefing to prioritize problems. Cognitive walkthroughs similarly involve walking through usage scenarios to identify learnability issues. Standards inspections check for compliance with specific standards.

1. IM2044 – Week 9: Lecture
Dr. Andres Baravalle
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2. Outline
• Design rules: principles, standards and
guidelines
• Usability inspections

3. Design rules: principles,
standards and guidelines
• Design rules are mechanism to restrict the
domain of design options
– Usability-related principles, standards and guidelines
support the developer
• Principles
– General understanding of design as a subject area
• Standards and guidelines
– Direction for design
• Design patterns
– Capture and reuse design knowledge

4. Types of design rules
• Principles
• Standards
– Specific design rules
– High authority
– Limited application
increasing generality
– Abstract design rules
– Low authority
– High generality
increasing generality
• Design rules differ in generality and authority
G uide line s
increasing authority
S ta nda rds
• Heuristics and guidelines
– Lower authority
– More general application
increasing authority

5. Design principles
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6. Principles to support usability
• Learnability
– The ease with which new users can begin effective
interaction and achieve maximal performance
• Flexibility
– The multiplicity of ways the user and system
exchange information
• Robustness
– The level of support provided the user in determining
successful achievement and assessment of goaldirected behaviour

7. Principles of learnability
• Predictability
– Determining effect of future actions based on
past interaction history
• Synthesizability
– Assessing the effect of past actions
– Immediate vs. eventual honesty

8. Principles of learnability (2)
• Familiarity
– How prior knowledge applies to new system
• Generalizability
– Extending specific interaction knowledge to
new situations
• Consistency
– Likeness in input/output behaviour arising
from similar situations or task objectives

9. Principles of flexibility
• Dialogue initiative
– Freedom from system imposed constraints on input
dialogue
• Multithreading
– Ability of system to support user interaction for more
than one task at a time
– Concurrent vs. interleaving; multimodality
• Task migrability
– Passing responsibility for task execution between
user and system

10. Principles of flexibility (2)
• Substitutivity
– Allowing equivalent values of input and output
to be substituted for each other (e.g. text and
audio)
– Representation multiplicity
• Customizability
– Modifiability of the user interface by user
(adaptability) or system (adaptativity)

11. Principles of robustness
• Observability
– Ability of user to evaluate the internal state of
the system from its perceivable representation
• Recoverability
– Ability of user to take corrective action once
an error has been recognized
– Reachability; forward/backward recovery;
commensurate effort

12. Principles of robustness (2)
• Responsiveness
– How the user perceives the rate of
communication with the system
• Task conformance
– Degree to which system services support all
of the user's tasks
– Task completeness; task adequacy

13. Design standards, guidelines
and heuristics
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14. Standards
• Set by national or international bodies to
ensure compliance by a large community
of designers standards require sound
underlying theory and slowly changing
technology
• Examples include:
– W3C HTML and CSS standards
– ISO 6385:2004: Ergonomic principles in the
design of work systems

15. Guidelines and heuristics
• Guidelines are detailed rules for design,
often platform or task-specific
• (Usability) heuristics are principles and
rules of thumb that govern the overall
design approach
– Many textbooks and reports full of guidelines
and heuristics
– Understanding justification for guidelines aids
in resolving conflicts

16. Usability inspections
• Usability inspection methods are based on
having evaluators inspecting an user
interface
• Usability inspection methods aim to
examine usability-related aspects of an
user interface, even if the interface has not
been yet developed
– Can be used to perform usability evaluations
in the initial stages of the development
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17. Usability inspections (2)
• Heuristic evaluation and walkthroughs are
the most common usability inspection
methods
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18. Heuristic evaluations
• Heuristic evaluation is a method that
requires some usability specialists to
judge whether each element of an user
interface follows established usability
principles and guidelines
– E.g. Jakob Nielsen’s heuristics
• Heuristics being developed for mobile
devices, wearables, virtual worlds, etc.
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19. Heuristic evaluations: stages
• Briefing session to tell experts what to do.
• Evaluation period of 1-2 hours in which:
– Each expert works separately
– Take one pass to get a feel for the product
– Take a second pass to focus on specific features
• Debriefing session in which experts work
together to prioritize and categorise the
problems
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20. Nielsen’s heuristics
• Developed by Jacob Nielsen in the early
1990s.
– Based on heuristics distilled from an empirical
analysis of 249 usability problems.
– These heuristics have been revised for
current technology – and we will discuss them
more in depth in the tutorial
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21. Nielsen’s heuristics: discount
evaluations
• An heuristic evaluation is referred to as
discount evaluation when 5 evaluators
are used
– Empirical evidence suggests that on
average 5 evaluators identify 75-80% of
usability problems on generalist web
sites
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22. Heuristic evaluations:
advantages and problems
• Few ethical & practical issues to consider
because users not involved
– Can be difficult & expensive to find experts
– Experts should have knowledge of application domain
& of the evaluation method used
• Critical points:
– Important problems may get missed
– Focus can be lost on trivial problems
– Experts have biases
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23. Cognitive walkthroughs
• Focus on ease of learning
• Designer presents an aspect of the design
& usage scenarios
• Expert is told the assumptions about user
population, context of use, task details.
• One or more experts walk through the
design prototype with the scenario.
• Experts are guided by 3 questions
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24. The 3 questions
• Will the correct action be sufficiently
evident to the user?
• Will the user notice that the correct action
is available?
• Will the user associate and interpret the
response from the action correctly?
As the experts work through the scenario
they note problems.
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25. Pluralistic walkthrough
• Variation on the cognitive walkthrough
theme.
– Performed by a team
• The panel of experts begins by working
separately
• Then there is managed discussion that
leads to agreed decisions.
• The approach lends itself well to
participatory design
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26. Feature inspection
• Feature inspection is a technique that focuses
on the features of a product or of a web site
– A group of inspectors that are given some use cases
and are asked to analyse each feature of the web site
for what regards availability, understandability, and
other aspects of usability
– This technique is better in the middle stages of
development, when features are known but the
artefact cannot be evaluated with methods as lab
experiments.
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27. Standards inspection
• Standards inspection is a technique used to
ensure the compliance of a web site against
some standard
• A usability professional with extensive
knowledge of the relevant standards inspects a
web site for compliance
• Different standard inspections can be run on the
same artefact
– Nielsen’s heuristics include standards inspection
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28. And now…
• You have had an overview of a wide
selection of usability evaluation methods
– And you are ready to use them in your
assignment
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