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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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