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Chapter 11. Object-Oriented Databases Database Systems: Design, Implementation, and Management, Fifth Edition, Rob and Coronel. In this chapter, you will learn:. What basic concepts govern OO systems What effect OO concepts are likely to have on data modeling and design

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Chapter 11

Chapter 11

Object-Oriented Databases

Database Systems: Design, Implementation, and Management, Fifth Edition, Rob and Coronel


In this chapter you will learn
In this chapter, you will learn:

  • What basic concepts govern OO systems

  • What effect OO concepts are likely to have on data modeling and design

  • How OO features are related to the more traditional relational and E-R models

  • What the basic features of an OO database management system (OODBMS) are

  • About the advantages and disadvantages of OODBMSs

Database Systems: Design, Implementation, & Management, 5th Edition, Rob & Coronel


Object orientation
Object Orientation

  • Object Orientation

    • Set of design and development principles

    • Based on autonomous computer structures

      known as objects

  • OO Contribution areas

    • Programming Languages

    • Graphical User Interfaces

    • Databases

    • Design

    • Operating Systems

Database Systems: Design, Implementation, & Management, 5th Edition, Rob & Coronel


Evolution of oo concepts
Evolution of OO Concepts

  • Concepts stem from object-oriented programming languages (OOPLs)

    • Ada, ALGOL, LISP, SIMULA

  • OOPLs goals

    • Easy-to-use development environment

    • Powerful modeling tools for development

    • Decrease in development time

    • Make reusable code

  • OO Attributes

    • Data set not passive

    • Data and procedures bound together

    • Objects can act on self

Database Systems: Design, Implementation, & Management, 5th Edition, Rob & Coronel


Oo concepts objects
OO Concepts: Objects

  • Abstract representation of a real-world entity

    • Unique identity

    • Embedded properties

    • Ability to interact with other objects and self

  • OID

    • Unique to object

    • Not a primary key

  • Attributes

    • Called instance variables

    • Domain

  • Object state

    • Object values at any given time

Database Systems: Design, Implementation, & Management, 5th Edition, Rob & Coronel


Oo concepts objects con t
OO Concepts: Objects (con’t.)

  • Methods

    • Code that performs operation on object’s data

    • Has name and body

  • Messages

    • Invokes method

    • Sent to object

  • Classes

    • Collection of similar objects

    • Shares attributes and structure

  • Protocol

    • Represents object’s public aspect

Database Systems: Design, Implementation, & Management, 5th Edition, Rob & Coronel


Oo concepts objects con t1
OO Concepts: Objects (con’t.)

  • Class hierarchy

    • Code that performs operation on object’s data

    • Has name and body

Database Systems: Design, Implementation, & Management, 5th Edition, Rob & Coronel


Object characteristics
Object Characteristics

Figure 11.7

Database Systems: Design, Implementation, & Management, 5th Edition, Rob & Coronel


Class hierarchy
Class Hierarchy

  • Superclass

  • Subclass

  • Class lattice

Figure 11.8

Database Systems: Design, Implementation, & Management, 5th Edition, Rob & Coronel


Inheritance
Inheritance

  • Ability of object to inherit the data structure and behavior of classes above it

  • Single inheritance

    • Class has one immediate superclass

Figure 11.9

Database Systems: Design, Implementation, & Management, 5th Edition, Rob & Coronel


Inheritance con t
Inheritance (con’t.)

  • Multiple

    • Class has more than one immediate superclass

Figure 11.10

Database Systems: Design, Implementation, & Management, 5th Edition, Rob & Coronel


Method overriding
Method Overriding

  • Method redefined at subclass level

Figure 11.12

Database Systems: Design, Implementation, & Management, 5th Edition, Rob & Coronel


Polymorphism
Polymorphism

Allows different objects to respond to same message in different ways

Figure 11.13

Database Systems: Design, Implementation, & Management, 5th Edition, Rob & Coronel


Abstract data types adt
Abstract Data Types (ADT)

  • Describes a set of similar objects

  • Differs from conventional data types

    • Operations are user-defined

    • Uses encapsulation

  • Definitions needed for creation

    • Name

    • Data representation

    • Abstract data type operations and constraints

Database Systems: Design, Implementation, & Management, 5th Edition, Rob & Coronel


Object classification
Object Classification

  • Simple

    • Only single-valued attributes

    • No attributes refer to other object

  • Composite

    • At least one multivalued attribute

    • No attributes refer to other object

  • Compound

    • At least one attribute that references other object

  • Hybrid

    • Repeating group of attributes

    • At least one refers to other object

Database Systems: Design, Implementation, & Management, 5th Edition, Rob & Coronel


Characteristics of oodm
Characteristics of OODM

  • Supports complex objects

  • Must be extensible

  • Supports encapsulation

  • Exhibit inheritance

  • Supports object identity

Database Systems: Design, Implementation, & Management, 5th Edition, Rob & Coronel


Oo vs e r model components
OO vs. E-R Model Components

Table 11.3

Database Systems: Design, Implementation, & Management, 5th Edition, Rob & Coronel


Shared representation for all objects of the class person
Shared Representation for all Objects of the Class Person

Figure 11.14

Figure 11.15

Database Systems: Design, Implementation, & Management, 5th Edition, Rob & Coronel


Referential sharing of objects
Referential Sharing of Objects

Figure 11.19

Database Systems: Design, Implementation, & Management, 5th Edition, Rob & Coronel


Class subclass relationship
Class-Subclass Relationship

Figure 11.21

Figure 11.20

Database Systems: Design, Implementation, & Management, 5th Edition, Rob & Coronel


Interobject relationships
Interobject Relationships

  • Attribute-Class Link

  • Object’s attribute references another object

  • Relationship Representation

    • Related classes enclosed in boxes

    • Double line on right side indicates mandatory

    • Connectivity indicated by labeling each box

      • 1:M

      • M:N

      • M:N with an Intersection Class

Database Systems: Design, Implementation, & Management, 5th Edition, Rob & Coronel


1 1 and 1 m relationships
1:1 and 1:M Relationships

Figure 11.24

Database Systems: Design, Implementation, & Management, 5th Edition, Rob & Coronel


Employee dependent relationship
Employee-Dependent Relationship

Figure 11.25

Database Systems: Design, Implementation, & Management, 5th Edition, Rob & Coronel


Representing the m n relationship
Representing the M:N Relationship

Figure 11.26

Database Systems: Design, Implementation, & Management, 5th Edition, Rob & Coronel


Representing the m n relationship with associated attributes
Representing the M:N Relationship with Associated Attributes

Figure 11.27

Database Systems: Design, Implementation, & Management, 5th Edition, Rob & Coronel


Representing the m n relationship with intersection class
Representing the M:N Relationship with Intersection Class

Figure 11.28

Database Systems: Design, Implementation, & Management, 5th Edition, Rob & Coronel


Object space representation
Object Space Representation

Figure 11.29

Database Systems: Design, Implementation, & Management, 5th Edition, Rob & Coronel


Late and early binding
Late and Early Binding

  • Late binding

    • Data type of attribute not known until runtime

    • Allows different instances of same class to contain different data types for same attribute

  • Early binding

    • Allows database to check data type at compilation or definition time

Database Systems: Design, Implementation, & Management, 5th Edition, Rob & Coronel


Oodm vs e r data models
OODM vs. E-R Data Models

  • Object, Entity, and Tuple

    • OODM object has behavior, inheritance, and encapsulation

    • OO modeling more natural

  • Class, Entity Set, and Table

    • Class allows description of data and behavior

    • Class allows abstract data types

  • Encapsulation and Inheritance

    • Object inherits properties of superclasses

    • Encapsulation hides data representation and method

Database Systems: Design, Implementation, & Management, 5th Edition, Rob & Coronel


Oodm vs e r data models con t

Object ID

Not supported in relational models

Relationships

OODM

Interclass references

Class hierarchy inheritance

Relational models

Value-based approach

Access

Relational models

SQL

OODM

Navigational

Set-oriented access

OODM vs. E-R Data Models (con’t.)

Database Systems: Design, Implementation, & Management, 5th Edition, Rob & Coronel


Oodbms
OODBMS

  • Database management system integrates benefits of typical database systems with OODM characteristics

  • Handles a mix of data types

  • Follows OO rules

  • Follows DBMS rules

Database Systems: Design, Implementation, & Management, 5th Edition, Rob & Coronel


Oo and database design
OO and Database Design

  • Provides data identification and the procedures for data manipulation

  • Data and procedures self-contained entity

  • Iterative and incremental

  • DBA does more programming

  • Lack of standards

Database Systems: Design, Implementation, & Management, 5th Edition, Rob & Coronel


Oodbms advantages
OODBMS Advantages

  • More semantic information

  • Support for complex objects

  • Extensibility of data types

  • May improve performance with efficient caching

  • Versioning

  • Reusability

  • Inheritance speeds development and application

  • Potential to integrate DBMSs into single environment

Database Systems: Design, Implementation, & Management, 5th Edition, Rob & Coronel


Oodbms disadvantages
OODBMS Disadvantages

  • Strong opposition from the established RDBMSs

  • Lack of theoretical foundation

  • Throwback to old pointer systems

  • Lack of standard ad hoc query language

  • Lack of business data design and management tools

  • Steep learning curve

  • Low market presence

  • Lack of compatibility between different OODBMSs

Database Systems: Design, Implementation, & Management, 5th Edition, Rob & Coronel


Oo influences on relational model
OO Influences on Relational Model

  • Extensibility of new user-defined (abstract) data types

  • Complex objects

  • Inheritance

  • Procedure calls (rules or triggers)

  • System-generated identifiers (OID surrogates)

Database Systems: Design, Implementation, & Management, 5th Edition, Rob & Coronel


The next generation of dbms
The Next Generation of DBMS

  • Object-oriented database systems

  • Artificial intelligence systems

  • Expert systems

  • Distributed database

  • The Internet

Database Systems: Design, Implementation, & Management, 5th Edition, Rob & Coronel


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