Interaction Design Process
Lecture 5
Chapter 3 (Heim)
COMPSCI 345 S1 C and SoftEng 350 S1 C
Interaction Design Process
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Iterative Design
User-Centered Design
Interaction Design Models
Overview of Interaction Design Models
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© Heim 2008
Iterative Design
• Interaction design is an iterative
process
– One step forward, two steps back
• The knowledge path is constantly
moving forward
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© Heim 2008
User-Centered Design (UCD)
• The objective of UCD is to develop a design
framework that enables interaction designers
to build more usable systems.
• Design should emerge from the user’s
– tasks
– goals
– environment
• Focuses on human-centric issues
– cognition
– perception
– physical attributes and conditions
• user
• environment
© Heim 2008
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User-Centered Design
• The basic tenets of user-centered
design:
– Early focus on users and their tasks
– Continuous evaluations to determine ease
of learning and ease of use
– Iterative design
• KNOW YOUR USER
•User Participation
•Walkthroughs
•Focus Groups
•Ethnographic Observations
•Questionnaires
•Expert Evaluations
•Usability Testing
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© Heim 2008
Interaction Design Models
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Waterfall Model
Spiral Model
Dynamic Systems Development Method
Prototype-Based Models
Discount Usability Engineering
Contextual Inquiry
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© Heim 2008
Waterfall Model
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Analysis and Coding
Small projects
Programmers are the users
Requirements are fixed
Not user-centered
Time sensitive
– Early completion of requirements
documentation
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© Heim 2008
Waterfall Model
• Advantages of the waterfall model:
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Highly disciplined process of documentation
Easily observable development progress
Easy to create budget
Consistent review process
• Disadvantages of the waterfall model:
– Document centric; can be difficult for
customer to understand
– Not user centered
– Makes assumptions about requirements
that are inflexible
© Heim 2008
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Spiral Model
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More flexible
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Centered on risk reduction
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Incorporates prototype
development
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Encourages iteration
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Breaks project into
subprojects identifying
specific risks
© Heim 2008
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Spiral Model
• Advantages
– Appropriateness for large-scale enterprise systems
– Flexibility in terms of its sensitivity to the dynamic
nature of the software industry
– High sensitivity to risk at each stage of development
• Disadvantages
– Complex nature makes it difficult for customers to
grasp
– Requires extensive information regarding risk
assessment
– Undetected risks can be problematic
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© Heim 2008
Dynamic Systems Development
Method (DSDM)
• Time-sensitive
– Time frame and allocated resources are
fixed
• Functional requirements are flexible
• Business-centered
– Main focus
on-time delivery
of high-quality
software for current
business needs
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© Heim 2008
Dynamic Systems Development
Method (DSDM)
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The DSDM framework recognizes nine
principles:
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2.
3.
4.
5.
6.
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Active user involvement is imperative.
The team must be empowered to make decisions.
The focus is on frequent delivery of products.
Fitness for business purpose is the essential criterion
for acceptance of deliverables.
Iterative and incremental development is necessary
to converge on an accurate business solution.
All changes during development are reversible.
Requirements are baselined at a high level.
Testing is integrated throughout the life cycle.
Collaboration and cooperation among all
stakeholders is essential.
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© Heim 2008
Prototype-Based Models
• Prototypes are used to develop,
demonstrate and test design ideas
• Appropriate for small-scale projects
• Enable discussions of:
– Look and feel
– Information flow
- Scope
- Product concept
• Throwaway Prototyping Model
– Used to elicit requirements
• Evolutionary Prototyping Model
– Trial and error method
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© Heim 2008
Prototype-Based Models
• Advantages of prototyping include the
following:
– Easy for users to give feedback
– Reduced development time and cost
– Involvement of the user in the development
process
• Disadvantages of prototyping include
the following:
– Can be viewed by client as the final product
– May lead to insufficient analysis due to the
ease of development
– Difficult for developers to discard and start
creating the final product from scratch
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© Heim 2008
Discount Usability Engineering
(DUE)
• Jakob Nielsen (1994) argued that the
benefits derived from even small
amounts of user testing would have a
significant impact on the usability of the
design.
• DUE is based on the use of the following
three techniques:
– Scenarios
– Simplified thinking aloud
– Heuristic evaluation
© Heim 2008
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Discount Usability Engineering
(DUE)
• Nielsen suggested that the number of problems
that could be identified from a usability test with n
users can be calculated according to the following
equation:
N [1-(1-L)^n]
where:
N total number of usability problems in a design
L proportion of usability problems discovered
with a single participant
(typical value for L is 31% based on their
research)
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© Heim 2008
Discount Usability Engineering
(DUE)
• Nielsen proposed a set of 10 usability
heuristics that could be used by designers
to investigate and document usability
problems.
– DUE requires some experience
– Should be done by a few reviewers to avoid
personal bias
• Will help to indicate issue frequency
– Should be done early in the design process
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© Heim 2008
Contextual Inquiry
• Involves
– Observation, Inquiry and Interpretation
• It is based on four main principles:
– Context
• how and why people use software products
– Partnership
• partnering with a typical user in a master/apprentice
relationship.
– Focus
• Observations are focused on collecting information on
tools/artifacts/terminology/sequences/methods/interaction
s
– Interpretation
• Use of affinity diagrams to sort, organise and prioritise
information
• Create models of communication flows, information
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sequences,
physical
environments
and
corporate
culture
© Heim 2008 structures which lead to conceptual models of design.
Overview of Interaction Design
Models
• Elements that appear in many of the
standard models
– Cost and risk analysis
– Observation
– Task analysis
– Requirements assessment
– Conceptual design
– Physical design
– Prototyping
– Evaluation
– Usability testing
– Implementation
© Heim 2008
– Maintenance
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The Design Process Model
• Discovery phase questions
– What are the components of the project
– Who is involved
– What are the current work space and work
flow like
– What are the contextual and extraneous
factors that affect the work flow
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© Heim 2008
The Design Process Model
• Design—The design phase has two parts:
– Conceptual Design—What are the possible
ways in which the design can address the
needs of the problem space?
• Personas, Scenarios and Use cases, etc.
– Physical Design—What are the possible ways
that the conceptual design can be realized in
the real world?
• Low-fidelity prototypes
• Wireframes
• Functional prototypes
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© Heim 2008
The Design Process Model
• Evaluation questions
– How can we determine the relative merits of one design
over another
– How can we measure the success of a proposed design
– How can we get real users to give us feedback about a
proposed design
– How can we incorporate usability testing at the early
stages of the design process
• This is documented by the results of formal and
informal usability testing.
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© Heim 2008
Summary
• Interaction design development process
– Basic stages are discovery, development,
evaluation and implementation
• User centred development frameworks
help us to design more usable systems
– Taking into account the user’s abilities,
limitations, goals and environment.
• Next Lecture: Discovery (Heim ch. 4.1 –
4.2)
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Questions
• Describe the difference between the
throwaway prototype model and the
evolutionary prototype model.
• The requirements of any DSDM project
are prioritized using MoSCoW. Define
MoSCoW.
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