1. Informatics 121 Software Design I
Lecture 2
Duplication of course material for any commercial purpose without the explicit written permission of the professor is prohibited.

2. Announcements No discussion Friday TA office hours have been set
Design studio 1 comes out on Tuesday

3. Today Defining design Defining software design
Two fundamental challenges

4. Defining design
Decision making, in the face of uncertainty, with high penalties for error
To choose the things we use shall look as they do
A creative activity—it involves bringing into being something new and useful that has not existed previously
Relating product with situation to give satisfaction
The imaginative jump from present facts to future possibilities
To form a plan or scheme of, to arrange or conceive in the mind, … for later execution

5. Defining design To initiate change in man-made things
To plan or intend for a purpose
To work out a solution in one’s mind
The transition from possible solutions to a specific one …

6. Three themes Design focuses on identifying a novel envisioned future
Design involves deliberate decision making and planning; it is not simply acting out of impulse
Design decisions are consequential: there are stakeholders who must be satisfied with the result

7. Our definition
To decide upon a plan for a novel change in the world that, when realized, satisfies stakeholders

8. [stakeholders = audience + other stakeholders]
Design
designer
plan
maker
change in the world
other stakeholders
audience
experiences
[stakeholders = audience + other stakeholders]

9. Design a luxury airplane
designer
plan
maker
change in the world
other stakeholders
audience
experiences

10. Design a library designer plan maker change in the world
other stakeholders
audience
experiences

11. Design an award designer plan maker change in the world
other stakeholders
audience
experiences

12. Design fields Architecture design Graphic design Fashion design
Game design
Chip design
Car design
Urban design
Product design
Interior design …

13. Design fields Architecture design Graphic design Fashion design
Game design
Chip design
Car design
Urban design
Product design
Interior design …
Writing
Painting
Sculpting
Music composition …

14. Design fields Architecture design Graphic design Fashion design
Game design
Chip design
Car design
Urban design
Product design
Interior design …
Writing
Painting
Sculpting
Music composition …
Software design

15. Design designer plan maker change in the world audience experiences
other stakeholders

16. Software design designer plan maker change in the world
other stakeholders
audience
experiences

17. Software design software designer source code compiler*
runnable program
other stakeholders
users
experiences
[* or, at times, the person who installs and configures the software instead of the compiler]

18. Two fundamental challenges
The nature of software
The nature of people

19. Nature of software (Brooks)
Complexity
software is among the most complex people-made artifacts
Conformity
software has no laws of nature that simplify its existence; rather, it lives in a world of designed artifacts to which it must conform
Changeability
software is subject to continuous pressure to change
Invisibility
because the reality of software is not embedded into space, it is inherently unvisualizable

20. Nature of people Diversity Indiscernibility Familiarity Volatility
people differ in how they experience the world
Indiscernibility
experiences are distinctly mental in nature, with tangible reactions and signs not always matching the actual experience
Familiarity
people tend to be risk averse, sticking to role, organizational, and societal norms and values
Volatility
with every new exposure, people reinterpret and modify their opinions and expectations