1. Informatics 122 Software Design II
Lecture 2 André van der Hoek & Alex Baker
Duplication of course material for any commercial purpose without the explicit written permission of the professor is prohibited.
May 1, 2019 – 09:29:24
© 2007 University of California, Irvine – André van der Hoek

2. © 2007 University of California, Irvine – André van der Hoek
Today’s Lecture
Design aesthetics
Assignment 1 continued
May 1, 2019 – 09:29:24
© 2007 University of California, Irvine – André van der Hoek

3. © 2007 University of California, Irvine – André van der Hoek
Aesthetics
“a particular theory or conception of beauty or art : a particular taste for or approach to what is pleasing to the senses and especially sight” [Merriam-Webster]
May 1, 2019 – 09:29:24
© 2007 University of California, Irvine – André van der Hoek

4. © 2007 University of California, Irvine – André van der Hoek
Design Aesthetics
What makes a given software design “beautiful”?
What is it that makes someone appreciate a particular software design?
What are the qualities that determine whether a particular software design is “good” or “bad”?
What is it, then, that we can strive for in creating a software design that will help others in appreciating it?
May 1, 2019 – 09:29:24
© 2007 University of California, Irvine – André van der Hoek

5. © 2007 University of California, Irvine – André van der Hoek
Design Aesthetics
Some brainstorming…
May 1, 2019 – 09:29:24
© 2007 University of California, Irvine – André van der Hoek

6. © 2007 University of California, Irvine – André van der Hoek
Design Aesthetics
Different people will have a different aesthetic appreciation of different designs
as informed by their own, pre-existing knowledge
as informed by their own understanding of the design goals
as informed by their own ideas
Different roles in the software development project may have different aesthetic appreciation of different designs
coder
software performance engineer
software maintenance specialist
software tester …
May 1, 2019 – 09:29:24
© 2007 University of California, Irvine – André van der Hoek

7. © 2007 University of California, Irvine – André van der Hoek
Design Aesthetics
Subjective, as it should be
activities
goals (langs)
knowledge (langs)
ideas (langs)
tools
goals (langs)
representations (langs)
May 1, 2019 – 09:29:24
© 2007 University of California, Irvine – André van der Hoek

8. © 2007 University of California, Irvine – André van der Hoek
Design Aesthetics
Subjective, as it should be
But we need some kind of shared “language”, some common touchstones that we can use to:
understand the underlying implications of certain designs
understand the intentions of designers
effectively frame our communication about designs
I think all 3 of these are very important points actually, perhaps worth of their own slides?
May 1, 2019 – 09:29:24
© 2007 University of California, Irvine – André van der Hoek

9. Shared Design Aesthetics
Individual
Project
Organization
Nice!
School of Thought
Community
May 1, 2019 – 09:29:24
© 2007 University of California, Irvine – André van der Hoek

10. © 2007 University of California, Irvine – André van der Hoek
But…
…what kind of shared understandings exist?
…where do these shared understandings come from?
May 1, 2019 – 09:29:24
© 2007 University of California, Irvine – André van der Hoek

11. Purpose of Implementation Design
An implementation design is a road map
An implementation design describes a path from system design to the outcome
An implementation design describes what the implementers should do
An implementation design is a guide towards future change
May 1, 2019 – 09:29:24
© 2007 University of California, Irvine – André van der Hoek

12. Purpose of Implementation Design
An implementation design is a road map
understandable, unambiguous, consistent, helpful, …
An implementation design describes a path from system design to the outcome
correct, complete, concise, verifiable, effective, …
An implementation design describes what the implementers should do
elegant, partitionable, recomposable, resilient, …
An implementation design is a guide towards future change
evolvable, …
May 1, 2019 – 09:29:24
© 2007 University of California, Irvine – André van der Hoek

13. More of a Shared Understanding (Not Perfect!)
An implementation design is a road map
understandable, unambiguous, consistent, helpful, …
An implementation design describes a path from system design to the outcome
correct, complete, concise, verifiable, effective, …
An implementation design describes what the implementers should do
elegant, partitionable, recomposable, resilient, …
An implementation design is a guide towards future change
evolvable, …
May 1, 2019 – 09:29:24
© 2007 University of California, Irvine – André van der Hoek

14. Less of a Shared Understanding
An implementation design is a road map
understandable, unambiguous, consistent, helpful, …
An implementation design describes a path from system design to the outcome
correct, complete, concise, verifiable, effective, …
An implementation design describes what the implementers should do
elegant, partitionable, recomposable, resilient, …
An implementation design is a guide towards future change
evolvable, …
May 1, 2019 – 09:29:24
© 2007 University of California, Irvine – André van der Hoek

15. © 2007 University of California, Irvine – André van der Hoek
Approaches to Date
Enumerate objectives
Define principles
Provide strategies
May 1, 2019 – 09:29:24
© 2007 University of California, Irvine – André van der Hoek

16. © 2007 University of California, Irvine – André van der Hoek
Approaches to Date
Enumerate objectives
overall process
overall design
individual classes
Define principles
Provide strategies
May 1, 2019 – 09:29:24
© 2007 University of California, Irvine – André van der Hoek

17. Objectives for Overall Process
Apply rigor
Separate concerns
modularize
abstract
Anticipate change
Generalize
Work incrementally
May 1, 2019 – 09:29:24
© 2007 University of California, Irvine – André van der Hoek

18. Objectives for Overall Design
Strive for grouping related functionality (high cohesion)
Strive for ungrouping semi-related functionality (high cohesion)
Strive for reducing interdependency (low coupling)
May 1, 2019 – 09:29:24
© 2007 University of California, Irvine – André van der Hoek

19. Objectives for Class Design
Cohesion
Completeness
Convenience
Clarity
Consistency
May 1, 2019 – 09:29:24
© 2007 University of California, Irvine – André van der Hoek

20. © 2007 University of California, Irvine – André van der Hoek
Approaches to Date
Enumerate objectives
Define principles
keep it simple, stupid! (KISS)
information hiding
acyclic dependencies …
Provide strategies
May 1, 2019 – 09:29:24
© 2007 University of California, Irvine – André van der Hoek

21. Keep It Simple, Stupid! (KISS)
Nothing should be more complicated than absolutely essential and, even then, everything should be analyzed as to whether it can be done simpler
May 1, 2019 – 09:29:24
© 2007 University of California, Irvine – André van der Hoek

22. © 2007 University of California, Irvine – André van der Hoek
Information Hiding
Hide design decisions that are most likely to change, thereby protecting other parts of the program from change if the design decision is changed
May 1, 2019 – 09:29:24
© 2007 University of California, Irvine – André van der Hoek

23. © 2007 University of California, Irvine – André van der Hoek
Acyclic Dependencies
Structure packages (grouping classes and interfaces) of a software system in such a manner that the dependencies among them form a directed acyclic graph (DAG)
May 1, 2019 – 09:29:24
© 2007 University of California, Irvine – André van der Hoek

24. © 2007 University of California, Irvine – André van der Hoek
Approaches to Date
Enumerate objectives
Define principles
Provide strategies
program to the interface
refactor
apply software patterns
use aspects
May 1, 2019 – 09:29:24
© 2007 University of California, Irvine – André van der Hoek

25. Program to the Interface
Program to an interface, never directly to an implementation
Always wrap a class in an interface
May 1, 2019 – 09:29:24
© 2007 University of California, Irvine – André van der Hoek

26. © 2007 University of California, Irvine – André van der Hoek
Refactor
(to be discussed)
May 1, 2019 – 09:29:24
© 2007 University of California, Irvine – André van der Hoek

27. Apply Software Patterns
(to be discussed)
May 1, 2019 – 09:29:24
© 2007 University of California, Irvine – André van der Hoek

28. © 2007 University of California, Irvine – André van der Hoek
Use Aspects
(discussed in Informatics 102)
May 1, 2019 – 09:29:24
© 2007 University of California, Irvine – André van der Hoek

29. © 2007 University of California, Irvine – André van der Hoek
Approaches to Date
Enumerate objectives
Define principles
Provide strategies
May 1, 2019 – 09:29:24
© 2007 University of California, Irvine – André van der Hoek

30. Purpose of Implementation Design
An implementation design is a road map
understandable, unambiguous, consistent, helpful, …
An implementation design describes a path from system design to the outcome
correct, complete, concise, verifiable, effective, …
An implementation design describes what the implementers should do
elegant, partitionable, recomposable, resilient, …
An implementation design is a guide towards future change
evolvable, …
May 1, 2019 – 09:29:24
© 2007 University of California, Irvine – André van der Hoek

31. Purpose of Implementation Design
An implementation design is a road map
understandable, unambiguous, consistent, helpful, …
An implementation design describes a path from system design to the outcome
correct, complete, concise, verifiable, effective, …
An implementation design describes what the implementers should do
elegant, partitionable, recomposable, resilient, …
An implementation design is a guide towards future change
evolvable, …
The approaches to date help, but much more remains to be done
May 1, 2019 – 09:29:24
© 2007 University of California, Irvine – André van der Hoek

32. © 2007 University of California, Irvine – André van der Hoek
Why Aesthetics?
Aesthetics aims higher than “usable” or “complete” or …
It aims to set a bar for design for which we as professional designers should strive
designs that are elegant
designs that communicate their intent seamlessly
designs that overall exude an air of sophistication that sets them apart from ordinary designs
May 1, 2019 – 09:29:24
© 2007 University of California, Irvine – André van der Hoek

33. First Assignment Continued: Scrabble
You are to update your UML, object-oriented design for a software implementation of the game of Scrabble based on what you learned in class today, as you see fit
You should particularly pay attention that it will be others who will be reading and interpreting your design, and that you will not be able to clarify in person
May 1, 2019 – 09:29:24
© 2007 University of California, Irvine – André van der Hoek

34. First Assignment Continued: Scrabble
You should provide additional documentation beyond the raw UML diagrams, where needed
You should feel free to use any UML or diagramming tool
You should bring six printed copies of your design to class
Due: Thursday, October 4th, beginning of class
May 1, 2019 – 09:29:24
© 2007 University of California, Irvine – André van der Hoek

35. First Assignment Continued: Grading
Completeness
does your design provide an entire skeleton for the implementation?
in other words, does the implementer need to fill in any blanks or make any changes to classes, class interfaces, or associations?
Understandability
can someone pick it up and implement it?
Flexibility
can the design support future changes?
May 1, 2019 – 09:29:24
© 2007 University of California, Irvine – André van der Hoek