1. Informatics 223 Applied Software Design Techniques
Lecture 6
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2. Today
The data models
Expert practices
Defining design
Onward

3. The data models Tell us about the data models themselves
what do we see?
what roles do they play?
Tell us about the process of finding the data models
Tell us about the value of the data models

4. Experts are not afraid Experts focus on the essence
Experts address knowledge deficiencies
Experts go as deep as needed
Experts try the opposite
Experts do something (else)
Experts know when to stop
Experts build their own tools

5. Experts iterate Experts repeat activities
Experts generate alternatives
Experts explore different perspectives
Experts move among levels of abstraction
Experts rotate among subject pairs
Experts change notation deliberately
Experts pause

6. Our definition
To decide upon a plan for a novel change in the world that, when realized, satisfies stakeholders
But as we did so opportunistically, we quickly figured out we needed something to frame the discussion, what are they doing when they are doing this? So we arrived at design behaviors – things they do, things that recur, and things that have a definite purpose in the design meeting with respect to advancing the design at hand.

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

8. 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]

9. Feasibility and desirability
designer
plan
maker
change in the world
other stakeholders
audience
experiences

10. Feasibility and desirability
designer
plan
maker
change in the world
other stakeholders
audience
experiences
desirability

11. Four types of design desirability feasibility
what is it to accomplish?
how does one interact with it?
desirability
feasibility
what is its conceptual core?
what are its implementation details?

12. Four types of design what is it to accomplish? satisfactory experience
how does one interact with it?
satisfactory experience
plan for realization
change in the world
what is its conceptual core?
what are its implementation details?

13. Four types of software design
what is it to accomplish?
how does one interact with it?
application design
satisfactory experience
plan for realization
interaction design
change in the world
what is its conceptual core?
what are its implementation details?
architecture design
implementation design

14. Design an instant message system
what is it to accomplish?
how does one interact with it?
application design
satisfactory experience
plan for realization
interaction design
change in the world
what is its conceptual core?
what are its implementation details?
architecture design
implementation design

15. Design a word processor
what is it to accomplish?
how does one interact with it?
application design
satisfactory experience
plan for realization
interaction design
change in the world
what is its conceptual core?
what are its implementation details?
architecture design
implementation design

16. Design cycle
synthesize
analyze
evaluate

17. Design cycle goals constraints assumptions decisions ideas synthesize
analyze
evaluate

18. Goals
A goal represents an explicit acknowledgment of a desired result that the eventual design solution must achieve
Goals may be suggested by any of the stakeholders
client
other stakeholders
audience
designer
Goals change over time, and may or may not be (partially) addressed by the current state of the design solution

19. Example goals
The luxury airplane must be 10% more fuel-efficient than its predecessor
The library must be able to hold 250,000 books
The award must be representative of the professional society that is commissioning it

20. Constraints
A constraint represents an explicit acknowledgment of a condition that restricts the design project
Constraints may be suggested by any of the stakeholders
client
other stakeholders
audience
designer
Constraints change over time, and may or may not be (partially) met by the current state of the design project

21. Example constraints
The luxury airplane must weigh less than 50,000 pounds
The library must not violate federal disability laws
The award must cost less than $1000 to produce

22. Assumptions
An assumption represents a fact that is taken for granted, may or may not be true, and influences the design project
Assumptions may be made by any of the stakeholders
client
other stakeholders
audience
designer
Assumptions change over time, and may or may not be (partially) fulfilled by the current state of the design project

23. Example assumptions The average person weighs 85 kilograms
The library needs to serve the community with an area stocked with personal computers
The professional society’s logo is red and white, which therefore must be its preferred colors for the award

24. Decisions
A decision represents a specific choice of how to further the design solution, typically after some amount of consideration
Decisions are the sole responsibility of the designer, though they can be (heavily) influenced by other stakeholders
Decisions change over time, and new decisions may or may not (partially) align with the current state of the design project

25. Example decisions
The fuselage and wings of the luxury airplane shall be made out of carbon composites
The library shall have bookshelves that are not movable
The award shall be made out of colored glass

26. Idea
An idea represents a thought or opinion, ranging from highly unformed to fully formed, that potentially shapes the design solution
Ideas typically are the sole responsibility of the designer, though they may be inspired by many different sources
Ideas change over time, and new ideas may or may not (partially) align with the current state of the design project

27. Example ideas What if the luxury airplane had a shower on board?
Perhaps the library membership cards should have RFID tags, so a visitor can simply grab the books they want, walk by an automated scanner, and have their books be on loan
I am thinking that the award should be a variant of last year’s award

28. Design an instant message system
synthesize
goals
constraints
assumptions
decisions
ideas
analyze
evaluate

29. Design a word processor
synthesize
goals
constraints
assumptions
decisions
ideas
analyze
evaluate

30. Routine, adaptive, and original design projects
high
original
complexity
adaptive
routine
low
high
low
familiarity

31. Design is difficult!

32. In this class…
…we introduce the practices of expert software designers that help ameliorate these difficulties
…we study core ways in which software designers structure their solutions
…we practice!

33. Our focus application design interaction design architecture design
what is it to accomplish?
how does one interact with it?
application design
satisfactory experience
plan for realization
interaction design
change in the world
what is its conceptual core?
what are its implementation details?
architecture design
implementation design