Date post: | 06-Dec-2014 |
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Session 3
Understand and Use Object Oriented
Methods
OOAD with UML / Session 3 / 2 of 25
Review OOAD refers to the development of systems
with the base concept of objects and classes UML is a modeling tool used in
Information systems Technical systems Embedded systems Distributed systems System software Business Systems
SDLC refers to different phases in the software development process
OOAD with UML / Session 3 / 3 of 25
Objectives
Discuss the class diagram and object diagram
Represent the relationships between classes
Discuss the concept of object Model
Identify classes during analysis
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Class and Object Class - A class is a description of a
group of objects with common properties (attributes), behavior (Operations), relationships, and semantic
Object - An object represents an entity, either physical, conceptual, or software
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Class Diagram-1
Class Object
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Class Diagram-2 Class Names Class Attributes Class Methods Constraints Comment
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Representation of Relationship
Multiplicity-Multiplicity defines how many objects participate in a relationship
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Multiplicity & Navigation
Student Schedule
Navigation
Multiplicity
0..*1
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Aggregation An aggregation is a stronger form of relationship where
the relationship is between a whole and its parts
Student Schedule
Aggregation
WholePart
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Aggregation-Composition
Composition is a form of aggregation with strong ownership and coincident lifetimes of the part with the aggregate
Student Schedule
Aggregation
Whole Part
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Aggregation-Dependency A dependency relationship is a weaker form of
relationship
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Aggregation-Generalization
A specialization/generalization relationship is one, in which objects of the specialized element (the child) are substitutable for objects of the generalized element (the parent)
Superclass Subclass
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Association Association is a connection between classes
Professor University
Professor UniversityWorks for
Class
Association Name
Role Names
EmployerEmployee
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Constraints of Association
An association may have a name that is placed on, or adjacent to the association path
The name of the association should reflect the purpose of the relationship and be a verb phrase; the name of an association can be omitted, particularly if roles names are used. Names like “has” and “contains should be avoided”, as they add no information about what the relationships are between the classes.
Each end of an association is a role specifying the face that a class plays in the association (not a constraint). Each role must have a name, and the role names must be unique. The role name should be a noun indicating the associated object’s role in relation to the associating object.
The use of association names and role names are mutually exclusive: one should not use both an association name and role name. For each association, it needs to decide as to which conveys more information.
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Association Classes
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Qualified Association
Theatre Seat1 99
Theatre Seat1Row {1,2,…9}
Column {1,2,..11}
1
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Recursive Association
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Inheritance and Generalization-1
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Inheritance and Generalization-2
The mechanism for sharing attributes and operations using the principle of generalization is referred to as inheritance
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Same Association or Aggregation
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Interface
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Object Model
Language independent
Notation allowing the specification of classes, their data or attributes (private) and methods (public), inheritance
This diagram depicts the structural relationship and functional behavior of the classes
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Nouns in problem statement Knowledge of the problem
domain Use Cases Physical entities Devices Events Roles played Operational procedures Sites Organisational units
How to Identify Classes?
Tangible things Events Roles played Interactions Location Organizational Units The Requirements
statement Use Cases Application experts Studying the system
Similar systems Previous systems
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Candidate Classes
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Summary A class icon is a
rectangle with three sections within it
Association is a connection between classes
An interface is a collection of operations that are used to specify a service of a class or a component
Object Model generally deals with classes