1. Norman Chapter 6 Krug Chapter 7 A: Evolutionary Design
Jeff Offutt
SWE 205
Software Usability and Design

2. Losing Evolutionary Design
Pre-1850 : Hand-crafted objects
Design evolved over time, each new object better than the last
Very high production cost
1850s-2000s : Large-scale manufacturing
The same (flawed) design is quickly put into thousands of products
Very low production cost
1960s-2010
Making software perfect “out of the box”
Zero production cost
Manufacturing defeated evolutionary design!
27-Feb-19
© Jeff Offutt

3. Evolutionary Software Design
Pre-Web software design & production
Strive for a perfect design, expensive development
Deploy a new version ever 4 to 6 years
Evolution was very slow
Post-Web software production
Initial “pretty good” design and development
Faster evolution
Automatic updates of desktop applications
Software upgrades pushed out to mobile devices
Replacing chips in cars during oil changes
Internet of Things
We have resuscitated evolutionary design !
27-Feb-19
© Jeff Offutt

4. Example: Designing Public Faucets
Problem : People forget to turn off the water
Solutions :
Must hold the faucet on
One-handed washing, cannot use hot and cold simultaneously
Automatically turn off after X seconds
More expensive, less reliable, and what is X?
Foot pedal
Complicated plumbing, control is invisible, temperature and volume cannot be controlled
Sensor
Expensive, controls are invisible, temperature and volume cannot be controlled
27-Feb-19
© Jeff Offutt

5. Creeping Featurism Designers love to add more features
But how many do users really want ?
How many do users know how to use ?
On my old mobile phone, I used 16 of 31 top-level menu items
Roughly half of PPT (and I’m a heavy user!)
Excessive features make UIs harder to learn, slower to use, and more error-prone
Usability testing can reveal which features are used
27-Feb-19
© Jeff Offutt

6. In-class Discussion
With your near neighbors, discuss: How are TDD and evolutionary design related?
27-Feb-19
© Jeff Offutt