1. The Object Model Lecture OO02 Classes as Abstract Data Types
Understanding Classes and Objects

2. References
Ambler, S., The Object Primer, Cambridge Univ. Press, 2001, Chapter 1 & 2.
Booch, G., Object-oriented Analysis and Design, Benjamin Cumings, 1994, Chapter 1.
Gamma, E., et al, Design Patterns, Addison Wesley, 1994, Chapter 1

3. Teaching Points The “Kind-of” Hierarchy What is an object?
What is a class?
Your first pattern

4. Review What is an abstract data type?
How do multiple architectural views help to cope with complexity?
A new kind of hierarchy is a new “kind hierarchy

5. Decomposition Things or objects in the problem domain
It is all in the way we think about the problem

6. Abstractions Abstract data types Kinds of things Relationships
inheritance
aggregation
use

7. Hierarchy
Akind hierarchy
Apart hierarchy

9. Example: Decomposition of an aircraft as a complex system
Remember information-hiding!

10. The Object Oriented Paradigm
No longer a tree of process invocations
Now a network of cooperating objects

11. What is an Object? In-formally A tangible and/or visible thing
Something that may be apprehended intellectually
Something toward which thought or action is directed

12. What is an Object? An object has: State (properties, values)
Behavior (modifiers, iterators, selectors, constructors, destructors)
Identity (???)

13. What is a class? An abstraction or the Aessence@ of an object
represents a set of objects that share a common structure and common behavior (interface)
A kind-of-things
A single object is simply an instance of a class

14. Strengths of this kind of decomposition
Expression in vocabulary of the problem domain
Strong information hiding

15. What is a Pattern?
“A design pattern describes a commonly-recurring structure of communicating components that solve a general design problem in a particular context.”
Gamma, et al.

16. Composite Pattern May be used to describe: File system
Graphics objects
Aircraft Components
etc.

17. Teaching Points The “Kind-of” Hierarchy What is an object?
What is a class?
Your first pattern