Chapter 25 - 28
Object-Oriented Practices
Agenda
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Object-Oriented Concepts
Terminology
Object-Oriented Modeling Tips
Object-Oriented Data Models and DBMSs
OODBMS Manifesto
Object Management Architecture
Common Object Request Broker
Architecture
Object-Oriented Concepts
• Abstraction – encapsulation and information
hiding
– Identifying the essential aspects of an entity (Object)
– Abstract Data Type (ADT): interface part (operation)
implementation part (data structure)
• Encapsulation
– An object has data structure and operations
• Information hiding
– Internal details
– Data independence
Terminology
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Object Identity
Classes
Operations, methods & messages
Inheritance
Polymorphism
Object Identity (OID)
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System generated
Unique to that object
Invariant
Independent of the values of its attributes
Invisible to the user
Advantages:
– Fast, efficient, independent of content, not
changeable by user
Class
• Definition
– Group of objects with similar properties
(attributes), common behavior (methods),
similar relationship to other objects, and
common semantics.
• Diagram
– Box: class name, attributes, operations
(methods)
• Superclasses & subclasses
• Generalization & specialization
Inheritance
• Definition
– A subclass inherits the attributes, operations,
and association of its superclasses
• Types
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Single inheritance: one superclass
Multiple inheritance: two or more superclasses
Repeated inheritance: common superclass
Selective inheritance: limited number of
properties from the superclass
Operations Methods & Messages
• Operations
– Function or procedure may be applied to or by
objects in a class
• Methods
– The implementation of an operation for a class
• Messages
– Communication between objects to execution
of a method
Link & Association - 1
• Link
– A physical or conceptual connection between
objects
– Link attribute describes property of an
association
• Association
– A description of a group of links with common
structure and common semantics
– Has a name (roles for problem description)
• A link is an instance of an association
Link & Association - 2
• Qualified association
– The objects in a many role are partially or fully
disambiguated by an attribute called the
qualifier
– A small box on the end of the association line
near the source class
• Multiplicity
– The number of instances of one class that may
relate to a single instance of an associated class
– one, many, zero or one
Polymorphism
• Overloading
– The name of a method to be reused within a
class definition or across class definitions
• Overriding
– The name of property to be redefined in a
subclass
• Dynamic binding
– Runtime determination of object and method
Object Modeling Tips
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Scope
Simplicity
Layout of diagram
Name (descriptive, crisp, and unambiguous)
Association (foreign keys)
Multiplicity
Qualifiers
Review
Object-oriented DBMSs
• Object-oriented data model (OODM)
– A logical data model of objects supported in
object-oriented programming
• Object-oriented database (OODB)
– A persistent and sharable collection of objects
defined by an OODM
• Object-oriented DBMS (OODBMS)
– The manager of an OODB
OODBMS Manifesto - 1
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Support complex objects
Support object identity
Support encapsulation
Support types or classes
Support inheritance between types or
classes
• Support dynamic binding
OODBMS Manifesto - 2
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Completed computational DML
Extensible data types
Data persistence
Support very large databases
Support concurrent users
Backup & recovery
Support simple way of querying data
Object Management Architecture
(OMA)
• Object Model (OM)
– A design-portable abstract model for communicating with OMG
(Object Management Group)-compliant object-oriented systems
• Object Request Broker (ORB)
– Handles distribution of messages between application objects
(software bus)
• Object Services (concurrency control, security, persistence
etc.)
• Common Facilities (printing, e-mail etc.)
• Common Object Request Broker Architecture (CORBA)
– Enable client-server interaction with a specific implementation of
ORB
Points To Remember
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Object-Oriented Concepts
Terminology
Object-Oriented Modeling Tips
Object-Oriented Data Models and DBMSs
OODBMS Manifesto
Object Management Architecture
Common Object Request Broker
Architecture
Assignments
• Review chapters 5-6, 11-18, 25-27
• Read chapters 19 and 20
• Exam 3
– Date:
• Project
– Due date:
– Place:
End of MIS150
• Exam date: 12/9/03
• Study! Study! Study!
• Have a happy and safe holiday!!