1. Module 1: Introduction to OOAD
(Object-Oriented Analysis and Design)
Lawrence Chung
CS6359.OT1: Module 1

2. References
Object-Oriented Modeling and Design, Rumbaugh, et.al, Prentice Hall
The Unified Modeling Language User Guide, Booch, et.al.
Design Patterns; Elements of Reusable Object-oriented Software; Gamma, et.al.
Appying UML and Patterns, Craig Larman
Visual Modeling with Rational Rose and UML, Terry Quatrani 1998
Object-Oriented Methods: A Foundation, James Martin, et. al, 1995
Lawrence Chung
CS6359.OT1: Module 1

3. Objectives Why OO? What is OOAD? How to do OOAD? Lawrence Chung
CS6359.OT1: Module 1

4. Why Object-Oriented?
“The "software crises" came about when people realized the major problems in software development were not algorithmic, but were caused by communication difficulties and the management of complexity” [Budd]
The Whorfian Hypothesis:
The language in which an idea is thought or expressed colors or directs in a very emphatic manner the nature of the thought


What kind of language can alleviate difficulties with
communication & complexity well?
Lawrence Chung
CS6359.OT1: Module 1

5. Why Object-Oriented? – Consider Human Growth & Concept Formation
Communication & complexity about the problem and the solution, all expressed in terms of concepts in a language!
But then, What is CONCEPT? [Martin & Odell]
Consider Human Growth & Concept Formation
stage
concepts
infant
the world is a buzzing confusion
very young age
"blue" "sky“ (individual concepts)
"blue sky“ (more complex concept)
hypothesis: humans possess an innate capacity for perception
getting older
-> increased meaning, precision, subtlety, ...
the sky is blue only on cloudless days
the sky is not really blue
it only looks blue from our planet Earth
because of atmospheric effects
elaborate conceptual constructs
Concept formation: from chaos to order!
Lawrence Chung
CS6359.OT1: Module 1

6. Why Object-Oriented? - concepts and objects
So, concepts are needed to bring order into the problem and the solution
But, What is CONCEPT? [Martin & Odell] [Novak, 1984, Cambridge University Press]
Study of a first grade class
When given a list of concepts (water, salt water, Oceans, Penguins,...),
Harry constructed a concept diagram through which he understands his world and communicates meaning
A "concept" is an idea or notion that we apply to the things, or objects, in our awareness
Lawrence Chung
CS6359.OT1: Module 1

7. Why Object-Oriented? … for Conceptual Modeling Reasons
What kind of language is used to create this concept diagram, or Harry’s mental image?
What are the building blocks of Harry’s perception of this piece of reality,
represented in his mind/brain?
Object-Orientation (OO) = Being “conceptual”
OO analysis & design = “Conceptual” analysis & design
But for what?
for Modeling!
Analysis for Model of the problem
design for Model of the solution
“conceptual” analysis for “conceptual” model of the problem
“conceptual” design for “conceptual” model of the solution
Lawrence Chung
CS6359.OT1: Module 1

8. Why Object-Oriented -> What is a model?
A model is a simplification of reality.
E.g., a miniature bridge for a real bridge to be built
Well...sort of….but not quite
A model is our simplification of our perception of reality (that is, if it exists, otherwise it could be a mere illusion). Your perception, my perception, his, hers, …, => communication is not about reality but about your/my/his/her perception of reality => validation and verification hard but needed
A model is an abstraction (omitting tremendous amount of details) of something for the purpose of understanding, be it the problem or a solution.
A model (like Harry’s) is expressed in terms of concepts in a language!
Lawrence Chung
CS6359.OT1: Module 1

9. What is Object-Orientation
- Abstraction and Encapsulation
Abstraction
Focus on the essential
Focus on what an object “is and does”
Omits tremendous amount of details
Encapsulation
a.k.a. information hiding
Objects encapsulate:
state as a collection of instance variables
behavior as a collection of methods invoked by messages
Lawrence Chung
CS6359.OT1: Module 1

10. What is Object-Orientation
- Example of Abstraction and Encapsulation
Class Car
Attributes
Model
Location
Operations
Start
Accelerate
Lawrence Chung
CS6359.OT1: Module 1

11. What is Object-Orientation? - Object
A "concept" is an idea or notion that we apply to the things, or objects, in our awareness
An "object" is anything to which a concept applies.
Thing drawn from the problem domain or solution space.
E.g., a living person in the problem domain, a software component in the solution space.
A structure that
- has identity (i.e., discrete and distinguishable), and
- bundles together attributes (the data part, or state) and behavior (the function/code part).
It is an instance of a collective concept, i.e., a class.
Lawrence Chung
CS6359.OT1: Module 1

12. What is Object-Orientation? - Class
What is CLASS?
a collection of objects that share common properties, attributes, behavior and semantics, in general.
A collection of objects with the same data structure (attributes, state variables) and behavior (function/code/operations) in the solution space.
A blueprint or definition of objects.
A factory for instantiating objects.
The description of a collection of related components.
Classification
Grouping of common objects into a class
Instance.
An object created by a class.
Instantiation.
The act of creating an instance.
Cf. Containment.
Objects that contain other objects as components.
Lawrence Chung
CS6359.OT1: Module 1

13. What is generalization? What is over-generalization?
What is Object-Orientation
- Subclass vs. Superclass
Specialization
The act of defining one class as a refinement of another.
Subclass
A class defined in terms of a specialization of a superclass using inheritance.
Superclass
A class serving as a base for inheritance in a class hierarchy
Inheritance
Automatic duplication of superclass attribute and behavior definitions in subclass.
What is generalization? What is over-generalization?
Lawrence Chung
CS6359.OT1: Module 1

14. What is Object-Orientation? -State
What is STATE?
"State" is a collection of association an object has with other objects and object types.
What is STATE CHANGE?
A "state change" is the transition of an object from one state to another.
What is EVENT?
An "event" is a noteworthy change in state.
Lawrence Chung
CS6359.OT1: Module 1

15. What is Object-Orientation – More about Message
An object (sender) sends a request (message) to another object (receiver) to invoke a method of the receiver object’s.
A message is similar to a function call, but different
a message must somehow reference the intended recipient object
the recipient object only responds to the protocol, i.e., a predetermined set of messages defined by its class.
Data
Data
message Fn Fn
Sender object
Receiver object
Lawrence Chung
CS6359.OT1: Module 1

16. What is Object-Orientation? - Object-Oriented Application
Collection of discrete interacting objects
Objects have behavior and state
Inter-object communication through message passing
Data
Data Fn Fn
Data Fn
Lawrence Chung
CS6359.OT1: Module 1

17. What is OOAD?
Analysis — understanding, finding and describing concepts in the problem domain.
Design — understanding and defining software solution/objects that represent the analysis concepts and will eventually be implemented in code.
OOAD — Analysis is object-oriented and design is object-oriented. A software development approach that emphasizes a logical solution based on objects.
Lawrence Chung
CS6359.OT1: Module 1

18. Where to use OO in software lifecycle? Where in this course?
How to Do OOAD – Where to Use OO?
Software Lifecycle Review
Systems Engineering
Requirements Analysis
Quality Assurance
Project Planning
Maintenance
Architectural Design
Detailed Design
Implementation
Release
Where to use OO in software lifecycle? Where in this course?
Lawrence Chung
CS6359.OT1: Module 1

19. How to Do OOAD – OMT as Object-Oriented Methodology
OMT (Object Modeling Technique) by James Rumbaugh
Object Model: describes the static structure of the objects in the system and their relationships
-> Object Diagrams.
Dynamic Model: describes the interactions among objects in the system -> State Diagrams.
Functional Model: describes the data transformation of the system
-> DataFlow Diagrams.
Lawrence Chung
CS6359.OT1: Module 1

20. How to Do OOAD – OMT as Object-Oriented Methodology
OMT (Object Modeling Technique) by James Rumbaugh
Analysis: Model the real world showing its important properties; Concise model of what the system will do
System Design: Organize into subsystems based on analysis structure and propose architecture
Object Design: Based on analysis model but with implementation details; Focus on data structures and algorithms to implement each class; Computer and domain objects
Implementation: Translate the object classes and relationships into a programming language
Lawrence Chung
CS6359.OT1: Module 1

21. How to Do OOAD - Historical Perspective
OO Technology
Process Perspective
OO Prog. Languages (Smalltalk, C++)
just program!
OO Design (Booch)
design then program
Analyze (use case) first,
then design,
T then program
OO Analysis (Rumbaugh, Jacobson)
Lawrence Chung
CS6359.OT1: Module 1

22. How to Do OOAD - OO Development Processes
Some Popular OOAD Processes
Fusion
Hewlett Packard
Recommended Process and Models
ObjectSpace best practices
Larman’s experiences
The Rational Unified Process (RUP)
Rational; Booch, Jacobson, and Rumbaugh
Lawrence Chung
CS6359.OT1: Module 1

23. How to Do OOAD – One Good Way: Use (OO) Design Patterns
Reusable solutions to typical problems.
“Each design pattern systematically names, explains, and evaluates an important and recurring design in object-oriented systems.” [Gamma]
Name — identifies a particular pattern, creating a vocabulary.
Problem — identifies context when pattern should be applied.
Solution — an abstract description of a design problem along with a template object design that solves the problem.
Consequences — results and trade-offs of applying the pattern.
Lawrence Chung
CS6359.OT1: Module 1

24. Introduction to OOAD - Summary
Why
Software Crisis due to Communication and Complexity
Languages, Concepts, Models
OO for Conceptual Modeling
Historical Perspective of Modeling Paradigms
What
Fundamental OO Concepts
How
Design patterns & OO development processes
Lawrence Chung
CS6359.OT1: Module 1

25. Introduction to OOAD - Points to Ponder
How do you think your mental image is represented?
What kinds of languages are used for what purpose in our daily life?
What are the differences among a concept, a model and a language?
What are the differences between a language and a methodology?
Can we use C# for analysis?
If C++ is a language, does it model anything? If so, what?
What does a concept in C++ refer to (i.e., semantics)?
What does a concept in a (OO) design refer to?
What does a concept in an (OO requirements) analysis refer to?
Is the current OOAD for Functional Analysis and Design, or Non-Functional Analysis and Design?
What is the relationship between OO (Object-Orientation) and GO (Goal-Orientation), between OO and AO (Agent-Orientation), and between GO and AO?
Can you prove you and I communicate with each other perfectly?
Lawrence Chung
CS6359.OT1: Module 1

26. Module 1: Introduction to OOAD - Appendix
(Object-Oriented Analysis and Design)
Lawrence Chung
CS6359.OT1: Module 1

27. Why Object-Oriented – Why Do We Model?
To understand why a software system is needed, what it should do, and how it should do it.
To communicate our understanding of why, what and how.
To detect commonalities and differences in your perception, my perception, his perception and her perception of reality.
To detect misunderstandings and miscommunications For just about everything!
Lawrence Chung
CS6359.OT1: Module 1

28. Why Object-Oriented - Importance of Conceptual Modeling Once More
No reason to build a system for which there is no reason to -> understand the reason – part of the problem, hence analysis
No way to build a system for which there is no understanding of its structure, parts and relationships -> understand the solution, hence design
We build models of complex systems because we cannot understand such a system in its entirety…
Without conceptual models of complex systems, both problems and solutions, we cannot understand such a system in its entirety Object-Orientation is for conceptual modeling!
Cf. Representing people in a stack is not conceptual in the problem space.
Lawrence Chung
CS6359.OT1: Module 1

29. Why Object-Oriented - Who’s Behind Object-Orientation
Databases
Emphasis in Persistent Data
RelationalDB
Network DB
Hierarchical DB
OODB
Knowledge Representation (in A.I.)
Psychological Validity
Philosophical Validity
Computational Validity
ERD CM
SDM
ADT
Programming Languages
Emphasis in Efficiency
Simula, SmallTalk, C++, Protel, Java
ERD: Entity Relationship Diagram
SDM: Semantic Data Model
ADT: Abstract Data Type
CM: Conceptual Model
What role does Software Engineering play?
Lawrence Chung
CS6359.OT1: Module 1

30. Why Object-Oriented? - Communication & Complexity about Problem and Solution
So, let us try to Communicate well and Conquer the complexity well
But about what? …about what is really critical…
Experience shows:
DEFINING THE "PROBLEM" (analysis) is THE "PROBLEM“
ARCHITECTURAL DESIGN (the highest level of solution) can, literally, make it or break it (high-level design)
about analysis and design!
Common wisdom says: "Divide and Conquer"
-> decompose the problem & the solution into manageable parts
This can help (methodologically) with
adaptability, parallel development and deployment of the system, etc.
But still, what kind of language can alleviate difficulties with communication & complexity well about the analysis and the design, and suited well to the divide and conquer methodology?
Lawrence Chung
CS6359.OT1: Module 1

31. Why Object-Oriented - Who’s Behind Object-Orientation?
Lawrence Chung
CS6359.OT1: Module 1

32. Why Object-Oriented – Is OO A New Paradigm?
Paradigm: “way of looking at things”
Yes! OO does present a new way.
Programming Paradigms
Imperative Procedures & Algorithms
Function-oriented Mathematical functions
Logic-oriented Goals, predicate logic
Object-oriented Classes & Objects
Rule-oriented Expert systems
Constraint-oriented Invariant relations
Lawrence Chung
CS6359.OT1: Module 1

33. Why Object-Oriented – A New Paradigm with Evolving Object Orientation
OOP: Object-Oriented Programming
Simula (1967), Smalltalk (70’s), C++ (mid 80’s), Eiffel, Ada95, Turing, …
OOD: Object-Oriented Design
Taxis (1976), Adaplex, …, Grady Booch (1980)
OOA: Object-Oriented Requirements
RML (1981), James Rumbaugh (late 80’s)
OO-Databases (OODBs): ’s
OLE/DCOM, VisualBasic, CORBA, Java, UML: mid 90’s
.Net, C#, (eb/voice…/-)XML, J2EE: into 2000+
Lawrence Chung
CS6359.OT1: Module 1

34. Why Object-Oriented – Why Shift in Modeling Paradigm
From Functional
Functions as building blocks (fn: Input -> Output)
Algorithmic perspective
E.g., Lisp
To Object-Oriented
Objects as building blocks.
Conceptual perspective
from the vocabulary of the problem space for analysis
from the vocabulary of the solution space for design
Lawrence Chung
CS6359.OT1: Module 1

35. Why Object-Oriented – Functional  Object-Oriented
Identify concepts, in terms of both function and data together
Decompose system functionality Fn Fn
Data Fn
Data
e.g., Structure Chart
Lawrence Chung
CS6359.OT1: Module 1

36. Why Object-Oriented - Why Away From Functionally Structured Solution
Product quality is static or worsening, & increased testing
Increasing number of manpower - programmers
Long lead time, 2+ years for new commercial applications development
Significant amount of maintenance efforts & delay in adaptation to new hardware
Lawrence Chung
CS6359.OT1: Module 1

37. Why Object-Oriented - Programming Language Perspective
First Generation ( )
Fortran I
Second Generation ( )
Fortran II, Algol, Cobol
Third Generation ( )
PL/I, Pascal
Object-Oriented Languages
Smalltalk, C++, Java
Lawrence Chung
CS6359.OT1: Module 1

38. 1st Generation 2nd Gen Fortran II, Algol, Cobol Lawrence Chung
CS6359.OT1: Module 1

39. 3rd Generation Object Oriented
Data
Data Fn Fn
Data Fn
Allocation of functionality to objects
Shift from monolithic to decentralized control
Object-Oriented Programming Languages (OOPL)
PL/I, Pascal
Lawrence Chung
CS6359.OT1: Module 1

40. What is Object-Orientation - Abstract Class vs. Concrete Class
An incomplete superclass that defines common parts.
Not instantiated.
Concrete class.
Is a complete class.
Describes a concept completely.
Is intended to be instantiated.
Lawrence Chung
CS6359.OT1: Module 1

41. What is Object-Orientation – Operation vs. Message vs. Method
What is OPERATION?
An "operation" is a process that can be requested as a unit.
It is the mechanism for state change (i.e., event).
- Behavior across different kinds of objects
What is MESSAGE?
- specify what behavior receiver objects need to perform
- details of how to perform are left up to the receiver
- state information is accessed via messages
What is METHOD?
- specify how operations are to be carried out (hence implements a message)
- must have access to data
- can manipulate data directly
- Specific implementation of an operation by a certain class
Lawrence Chung
CS6359.OT1: Module 1

42. What is Object-Orientation
- Interfaces
All data should be hidden within a class.
make all data attributes private
provide public methods (accessor methods) to get and set the data
values
e.g. Grade information is usually confidential, hence it should be kept
private to the student. Access to the grade information should be
done through interfaces, such as setGrade() and getGrade()
Data
setGrade() Fn
getGrade()
Lawrence Chung
CS6359.OT1: Module 1

43. What is Object-Orientation
– How It All Fits Together?
An application is a set of objects that interact by sending messages
An object’s functionality is invoked by sending a message
An object’s functionality is implemented by methods
The data needed to support an object’s functionality is stored locally within an object
All application code must be associated with some object
Lawrence Chung
CS6359.OT1: Module 1

44. What is Object-Orientation - Polymorphism
The same operation may behave differently in different classes.
Objects of different classes respond to the same message differently.
In-state Student
payTuition ()
Out-of-State Student
Lawrence Chung
CS6359.OT1: Module 1

45. OOPL: Simula Developed for discrete event simulation (1967)
Simulation modeling is a hard problem for conventional languages
Simulated objects must interact and change state in many different and often unpredictable ways
Simulation can solve problems that are too complex for mathematical equations
Simulation objects are usually easy to identify and communicate via message passing
Lawrence Chung
CS6359.OT1: Module 1

46. OOPL: Smalltalk From Xerox PARC, by Alan Kay and Adele Goldberg
Towards a small language for anyone to use on a PC
Influenced by Simula: objects and classes
Influenced The WIMP interface
(Windows, Icons, Menu, Pointing device)
Influenced Apple’s design of Lisa and Macintosh
Lawrence Chung
CS6359.OT1: Module 1

47. OOPL: C++
From AT&T Bell Labs – invented by Bjorne Stroustrup
Adds object-oriented features to C
Classes in C++ correspond to types in C
Lawrence Chung
CS6359.OT1: Module 1

48. OOPL: Ada95 DOD support for embedded systems
Enforces Abstract Data Types (ADTs)
Data, operations on data, constraints on operations
E.g., formal specification languages - Larch, Z, VDM
Support for multitasking and exceptions
Large and complex
Lawrence Chung
CS6359.OT1: Module 1

49. OOPL: Java Like C++ in syntax Like Smalltalk in Structure and design
Without the drawbacks to C++ and Smalltalk
Frees the programmer from having to manage memory (accidental complexity)
Small footprint (memory requirement)
No pointers, pointer arithmetic, structs, typedefs, preprocessor directives (#define), malloc and free
With extensive type checking, true arrays with array bounds checking, null pointer checking, automatic garbage collection
Lawrence Chung
CS6359.OT1: Module 1