Iteration and prototyping

Iteration and prototyping hole topic.

1. iteration and prototyping
getting better …
… and starting well

2. prototyping
you never get it right first time
if at first you don’t succeed …
prototype evaluatedesign
re-design
done!
OK?

3. Prototyping JTB October 2004 3
Overview
Prototyping is a well understood and used
technique in engineering where novel
products are tested by testing a model
prototype
prototypes can be “throw away” (e.g., scale
models) or go into commercial use (Concorde!)
In software development prototypes can be
paper-based -
software-based

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What is Prototyping?
Essential element in user centred design
Is an experimental and partial design
Involves users in testing design ideas
Typically done very early in the design process
Can be used throughout the SDLC
Different types of prototyping are appropriate for
different stages of design
Product conceptualization –requirements –task
match user acceptance

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What is a prototype?
In interaction design it can be (among other things):
a series of screen sketches
a storyboard, i.e. a cartoon-like series of scenes
a Powerpoint slide show
a video simulating the use of a system
a lump of wood (e.g. PalmPilot)
a cardboard mock-up
a piece of software with limited functionality
written in the target language or in another
language

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Why Prototype?
Traditional software development: you can’t test until
you implement
Implementation is expensive, and there is nothing to
test until you have made that expenditure of effort
and schedule time
Result: any design errors are built in to the first thing
you can test, and it is very expensive to make
changes
Result: design errors, unless they are really bad, are
left in the product

7. Prototyping JTB October 2004 7
Breaking this implementation
paradox
Build a prototype of the basic functionality,
especially the interface
Test the prototype, which will uncover design
errors
Correct the errors
Repeat until you have a clean design
A major tool for improving usability
Heavily used in industry

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What to prototype?
•Work flow, task design
•Screen layouts and information
display
•Difficult, controversial, critical areas

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Low-fidelity Prototyping
•Uses a medium which is unlike the final medium,
e.g. paper, cardboard
•Is quick, cheap and easily changed
•Examples:
sketches of screens, task sequences, etc
‘Post-it’ notes
storyboards
‘Wizard-of-Oz’

10. 10
Prototyping Techniques
Paper Prototyping
Build it
Wizard of Oz
None are perfect --research lies in
creating tools & techniques that will
support rapid development and
evaluation

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Paper Prototyping
Sketch it out on paper
Fast, simple, effective
Simulate “computer”, get feedback about real use
Problems
Only really effective in well-constrained environments
Limited to desktop-like applications

12. 12
Build it
“sketch” it out on a computer
Existing prototyping tools & UI builders
Easy to create familiar look and feel
Problems
Existing tools limited to the desktop
Lack support for small, mobile devices
Lack support for variety of input and output
Familiar look and feel limited to our culture

13. 13
Wizard of Oz
Fake it
Only “prototype” the surface
Use a human “behind the curtain” to fake the rest
Particularly good for recognition
Problems
Easiest to do in a constrained environment
How does one “fake” rapid sensor input, etc?
Wizard must understand dialect, culture, etc.

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Paper Based Prototyping
Paper based prototypes
These have no functionality but can still be useful
for:-
Generating ideas
Gaining insights into what the user might want or is thinking
Eg a paper based design of a data entry screen
Storyboards and Snapshots
using “film-scripting” techniques to visualise
interactions between users and the system
This is very quick and cheap

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Storyboards
•Often used with scenarios, bringing more
detail, and a chance to role play
•It is a series of sketches showing how a
user might progress through a task using
the device
•Used early in design

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Sketching
•Sketching is important to low-fidelity
prototyping
•Don’t be inhibited about drawing ability.
Practice simple symbols

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•Index cards (3 X 5 inches)
•Each card represents one screen
•Often used in website development
Using index
cards

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Elements of a paper prototype
Menu Bar
Scroll
Bar
Secondary
Menu
Opening
Contents

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The home page
Pulldown
menu

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A second-level page

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Another second-level page

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After prototyping and user testing,
this is what their home page looked
like

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High-fidelity prototyping
•Uses materials that you would expect to be in
the final product.
•Prototype looks more like the final system than
a low-fidelity version.
•For a high-fidelity software prototype common
environments include Macromedia Director, Visual
Basic, and Smalltalk.
•Danger that users think they have a full
system…….see compromises

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Aims of Prototyping in
Software
The aim of prototyping is to resolve
uncertainty about
functional and user requirements
operation sequences
user support needs
required representations
“Look and Feel” of the interface
appropriateness of the design

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Software Prototyping
A software prototype will be a version of the
proposed system with limited functionality
Will differ from the final system in terms of
Size, reliability robustness & completeness
A software prototype
is “executable”
can be thrown away, or evolve
may serve many different purposes
should be “quick and dirty” (and cheap!)
is an integral part of user-centred design approaches
based on evaluation/modification

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Prototyping Techniques
The three major kinds of prototyping are
“Throw away” prototyping (a.k.a. “rapid
prototyping”)
used exclusively in requirements gathering
Incremental prototyping
not actually prototyping at all, but the delivery of
prioritised functions incrementally to a single, overall
design
Evolutionary prototyping (a.k.a “Rapid Application
Development, RAD)
as for incremental prototyping but with evolving design

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Rapid Prototyping
Aims to collect information on
requirements and the adequacy of
possible designs
Recognises that requirements are likely
to be inaccurate when first specified
The emphasis is on evaluating the
design before discarding it

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Incremental Prototyping
Final product is built as separate components one at
a time
There is one overall design for the system
It is partitioned into independent and smaller
components
Final product is released as a series of products
Eg General student details data module –the students
assessment profile module

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Evolutionary prototyping –RAD
As for incremental prototyping
Additions and amendments are made following
evaluation and the system is regenerated in its
amended form
In this case the prototype evolves into the final
system

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Other Prototyping Techniques
Full prototype
full functionality, lower performance than production software
Horizontal prototype
displays “breadth” of functionality, no lower level detail “back end”
support Eg. Database link
Vertical prototype
full functionality and performance of a “slice” or small part of the
system
•Two common types of compromise
•‘horizontal’: provide a wide range of functions, but
with little detail
•‘vertical’: provide a lot of detail for only a few
functions