OBJECT-ORIENTED MODEL 


MAJOR Elements:

   1. Abstraction

   2. Encapsulation

   3. Modularity

   4. Hierarchy


MINOR Elements:

   5. Typing

   6. Concurrency

   7. Persistence








OBJECT DEFINITION 

1. Has State

2. Is Characterized by its Operations (Methods)

3. Is a Unique Instance of some Class

4. Is Denoted by a Name

5. Has Restricted Visability

6. Can be viewed by either its Specification
        or Implementation







OBJECT CLASSIFICATION 

1. Actors

2. Servers

3. Agents





OPERATION (METHOD) CLASSIFICATION 


1. Modifier

2. Selector

3. Iterator

4. Constructor

5. Destructor






CLASS DEFINITION


"A Class is a set of Objects

that share a common structure

and a common behavior."



Parts of a CLASS

1. Public ( Ada, C++, Object Pascal, Smalltalk, CLOS, etc. )

2. Protected ( C++ )

3. Private ( Ada, C++, Smalltalk, CLOS, etc. )






GENERAL CLASS RELATIONSHIPS

1. Generalization

2. Aggregation

3. Association


PROGRAMMING LANGUAGE APPROACHES
TO CLASS RELATIONSHIPS

1. Inheritance

2. Using

3. Instantiation

4. Metaclass





INHERITANCE

1. Subclasses  &  Superclasses

2. Clients : Instances  &  Subclasses

3. Abstract Classes

4. Single

5. Multiple

6. Repeated







USING

1. Interface

2. Implementation

3. Cardinality -- 1 : n   or  m : n


INSTANTIATION

Templates and Generics  


METACLASS








RELATIONSHIPS BETWEEN
CLASSES and OBJECTS


1. Every Object is an Instance of Some Class

2. Classes are Static

3. Objects are Dynamic







CLASSES and OBJECTS
in ANALYSIS and EARLY DESIGN STAGES


1. Must Take the "Outside" View

2. Identify the KEY ABSTRACTIONS of the Problem

3. Invent the MECHANISMS of the Implementation







FUNCTIONAL SEMANTICS


1. Reusability

2. Complexity

3. Applicability

4. Implementation Knowledge


TIME AND SPACE SEMANTICS

(Only Necessary When Concurrency Present)






CLASSES and OBJECTS
in LATER DESIGN STAGES


1. Must Take the "Inside" View

2. Representation

3. Packaging




NAMING KEY ABSTRACTIONS (by "Convention")


1. Objects  =>  proper noun phrases

	shape    theSensor  the_sensor


2. Classes  =>  common noun phrases

	Sensors   Shapes


3. Modifier Ops  =>  active verb phrases

	draw   moveLeft   Move_Left


4. Selector Ops  =>  "to be" verbs

	isOpen   extent_of






OOA/OOD ADVANTAGES


1. Reuse

2. Reduces Change Impact

3. Reduces Development Risk

4. Human Cognition

5. Exploits OO Languages







OOA/OOD DISADVANTAGES


1. Start-up Costs

2. Reuse Costs

3. Performance Considerations