Principles of User-Centered
Design
CSCI 4800/6800
Feb. 1, 2006
What is design?
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Finding the right components of a physical structure
A goal-directed problem-solving activity
Simulating what we want to make or do before we
make or do it – as many times as may be necessary to
feel confident in the final result
Engineering design: “the use of scientific principles,
technical information and imagination in the definiton of
a mechanical structure, machine or system to perform
pre-specified functions with the maximum efficiency
and economy.
Approaches
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Formal specifications
Custom crafted / creative
User-Centered Design
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Principles
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Make user issues central in the design process
Carry out early testing and evaluation with users
Design iteratively
Methods for UCD
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Soft Systems Methodology (SSM)
Open Systems Task Analysis (OSTA)
Multiview
Star Life Cycle
Soft Systems Methodology
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Focuses on planning
Approach developed by Checkland, Schloes
’81, ’91
Emphasis : understand the problem and its
situation
SSM
Stages in SSM
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Stages 1 and 2 – obtain “rich expression” of
the problem: meetings with stakeholders
Stage 3 – obtain precise definition of the
system
Stage 4 – produce conceptual models: abstract
representation, “root definition”
SSM, “root definition”
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C - Clients (people who will benefit/suffer)
A - Actors (who is involved with system)
T - Transformation (purpose)
W - Weltanschauung/World View
(perspective from which root definition is
formulated)
• O - Owners (who has commissioned system)
• E - Environment
SSM
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Stage 5 – compare “root definition” of stage 4
with “rich expression” of stage 2; iterate until
gaps are filled
Stage 6 – identify changes
Stage 7 – recommend an action
SSM
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Benefits for HCI engineering:
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Identifies people, constraints, view of system
Develops conceptual models
Cooperative Design
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Participative design – users participate in
design process
Sociotechnical design – considers both social
and technical alternatives/solutions to/ aspects
of problems
OSTA – Open Systems Task Analysis (Eason,
Harker ’89)
OSTA
OSTA
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Specified together:
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Technical requirements
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Social system requirements
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System structure, functionality
Usability, acceptability
Goal:
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Provide method for understanding what occurs
when computer system is introduced into a working
environment
OSTA – Systems Analysis (top)
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Primary task stated (goals of group of workers identified)
Task inputs identified - usually come from outside the system character of inputs may vary & affect way system behaves
External environment - including physical environment, economic,
political conditions, demand for task output
Transformation processes described typically - object/action flowchart
of objects to be transformed & actions neccessary to transform them
with annotations
OSTA – technical and social
5. Social system analyzed
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6.
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Roles of people in relation to one another
Characteristics & qualities of users of new system
Technical system analyzed - how will new system be integrated with
others systems & what remains of the old system?
Performance satisfaction – for social system under new technical
systems
Requirements for new technical system, based on the task analysis
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Functionality, usability, acceptability
Problems:
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Need expert to guide the design process
Ability to integrate with other design
processes/methods
Need “right” organizational and political climate
Cost-effective???
Multiview
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Combines sociotechnical and soft-systems approaches
Stage 1: create PTM (primary task model) – similar to
“root def”
Stage 2: conceptual modeling of info flows/ structure,
produce FM (functional model), ER model, dataflow
models
Stage 3: design people tasks (PT), role sets (RS), and
computer task requirements (CTR)
Stage 4: design the HCI
Stage 5: technical design
Multiview
Multiview
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Provides more direction for system designers
Star Life Cycle
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No prescribed ordering of activities
Based on actual design practive of HCI
designers
Emphasis on prototyping and evaluation
Rapid prototyping, incremental development
The Star Life Cycle
Star Life Cycle
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Conceptual design – what is required? What
should system do? What data is required?
What will users need to know?
Physical design (formal design) : how to
achieve the conceptual design …
Methods for UCD
Example: Olympic Messaging Service
(1984 Los Angeles Olympic Games)
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Kiosks at which athletes could send &
receive voice messages among themselves
Or people from around the world could
send messages in to athletes & official
Twelve languages (no translation)
OMS - Process
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Paper scenarios of user interface prepared
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Comments from designers, management, prospective
users
Some functions altered, others dropped
Brief user guides prepared, tested, developed
iteratively (~200 iteratives)
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Simulations constructed & evaluated; help messages
designed
Simulations tested with users
OMS - Process
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Needed to add undo/backup button
Visit to village site, demos & interviews with
ex-olympians & others involved
Prototype developed & tested
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"Hallway" method to collect info on height &
layout of prototype kiosk
"Try-to-destroy-it" tests of robustness (CS
students)
OMS – summary
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Focus on users & tasks early in design process,
including user guides, help, & ensuring that user's
cognitive, social, & attitudinal characteristics are
understood & accomodated
Measure reactions by using prototype manuals,
interface, & other simulations of the system
Design iteratively
All usability factors must evolve together and be
under the responsibility of one control group
Example: Air Traffic Control System
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Original system
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Variety of info needed, each from own source some on desk, some on ceiling, some not in line of
sight
Dials
Closed Circuit TV
Temporary instructions
Air Traffic Control
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Desire: Integrated data display system
SAFETY (major concern)
"Upgradeable"
Variety of airports/local requirements
Modified info requirements
Layouts specific to controller & task
More color
Ability to add pages for specific local conditions
Simple editing facilities for updates
Example – Air Traffic Control
System
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Process:
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Evaluate controller’s task
Develop first-cut design
Establish user-systems design group
Concept testing, user feedback
Produce upgraded prototype
Road-show to five airports
Develop systems specification
build and install system
establish new needs