Chapter 18 Object Database Management Systems. McGraw-Hill/Irwin © 2004 The McGraw-Hill Companies, Inc. All rights reserved. Outline Motivation for object

Chapter 18Chapter 18Object Database Management Systems

McGraw-Hill/Irwin © 2004 The McGraw-Hill Companies, Inc. All rights reserved.

OutlineOutline

Motivation for object database management

Object-oriented principles Architectures for object database

management Object database definition and

manipulation in SQL:1999Object database definition and

manipulation in Oracle 9i


Motivation: Complex DataMotivation: Complex Data

Most relational DBMSs support only a few data types.

Many business applications require large amounts of complex data such as images, audio, and video.

The need to integrate complex data with simple data drives the demand for object database technology.


Motivation: Type System Motivation: Type System MismatchMismatchIncreasing use of database access in

procedural codeDifferent data types used in programming

languages versus DBMSsData type mismatch makes software more

difficult to develop. A relational DBMS cannot perform

elementary operations on complex data.


Application ExamplesApplication Examples

Dental Office Support Real Estate Listing Service Auto Insurance Claims


Object-Oriented PrinciplesObject-Oriented Principles

An object is a combination of data and procedures.

A class is a prototype that defines the variables and methods common to all objects of the class.

Three underlying principles: encapsulation, inheritance and polymorphism.


Encapsulation Encapsulation

Objects can be accessed only through their interfaces.

Classes can be reused rather than just individual procedures.

More complex classes can be defined using simpler classes.

Provides a form of data independence.


Bond Class ExampleBond Class Example

CLASS Bond {// VARIABLES: ATTRIBUTE Float IntRate; ATTRIBUTE Date Maturity;// METHODS: Float Yield();// Computes the Bond’s Yield };


Inheritance Inheritance Sharing of data and code among similar

classes (classes and subclasses). Inherit variables and methods from parent

classesWhen using the subclasses, the methods in

the parent classes can be used.Inheritance provides an improved

organization of software and incremental reusability.


Inheritance ExamplesInheritance Examples

ColorPointColor

Brighten

Pointx,y

DistanceEquals

CorporateRating

TheCompanyJunk

InheritanceRelationships

SubClasses

BondIntRateMaturity

Yield


Multiple Inheritance ExampleMultiple Inheritance Example SecuritySymbol

SecNameLastClose

StockOutShares

IssuedSharesYield

BondIntRateMaturity

Yield

Inheritanceconflict

ConvertibleConvPriceConvRatio


PolymorphismPolymorphism Ability of a computing system to choose

among multiple implementations Benefits

– Fewer, more reusable methods– incremental modification of code

Requesting a method execution involves sending a message to an object

Client-server processing and object-oriented computing are closely related.


Processing a MessageProcessing a Message

Message sent to ColorPointobject (CP1) to computedistance

ColorPoint classCP1 object

Point classDistance code

Message forwardedto parent class


BindingBinding

Associating an implementation with a message

Static binding– Performed at compile-time– More efficient but less flexible

Dynamic binding– Performed at run-time (late binding)– More flexible but less efficient


Strong Type CheckingStrong Type Checking

Complex expressions can involve many methods and objects

Incompatibility errors common in codeAbility to ensure that programming code

contains no incompatibility errors An important kind of error checking for

object-oriented coding


Programming Languages Programming Languages versus DBMSsversus DBMSs Programming languages have used object-

oriented principles for many years.Programming languages emphasize

software maintenance and code reusability.Object DBMSs are more recent.Encapsulation usually is relaxed so that an

object’s data can be referenced in a query. Inheritance mechanisms usually are simpler

in DBMSs


Architectures for Object Architectures for Object Database ManagementDatabase Management Adding object-oriented features to a DBMS is a

good idea Many approaches about the features to add and

how features should be added. Some approaches provide small extensions that

leave object features outside the DBMS. Other approaches involve a complete rewrite of

the DBMS to accommodate objects Marketplace will determine best approaches


Large Objects and External Large Objects and External SoftwareSoftware Storage of large objects in a database

along with external software to manipulate large objects.

Complex data are stored in a field using the BLOB (binary large object) data type.

The large object approach is simple to implement and universal.

The large object approach suffers from serious performance drawbacks.


Large Object ArchitectureLarge Object Architecture External software formanipulating complex data

Relational database

SQL statements

Simpledata

Complexdata

Database server

Simple andcomplex data


Specialized Media ServersSpecialized Media Servers The use of a dedicated server to manage

complex data outside of a database. Programmers use an application

programming interface (API) to access complex data.

Provide good performance for specific kinds of complex data.

The range of operations may be limited. May perform poorly when combining

simple and complex data.


Specialized Media Server Specialized Media Server ArchitectureArchitecture

Database

SQL statementsand results

Database server Media serverMedia base

API calls and results


Object database middleware Object database middleware

The use of middleware to manage complex data stored outside of a database along with traditional data stored in a database.

Provides a way to integrate complex data stored on PCs and remote servers with relational databases.

Object middleware can suffer performance problems because of a lack of integration with a DBMS.


Object Middleware ApproachObject Middleware Approach

DatabaseDatabase server Media server

Media base

Object middleware


API callsand results

SQL statements and results


Object Relational DBMS for Object Relational DBMS for User-Defined TypesUser-Defined Types A relational DBMS extended with an object

query processor for user-defined data types. Complex data is added as a user-defined

type.User-defined functions can be defined and

then used in SQL statements.SQL:1999 provides the standard for object

relational DBMSs. Provide good integration of complex data

but reliability may be a concern.


Component Architecture for Component Architecture for Object Relational DBMSsObject Relational DBMSs

Database

Object query processor(parser, optimizer, display

manager)



Relational kernel(transaction processing,

storage management, buffermanagement)


Object-Oriented DBMSObject-Oriented DBMS

A new kind of DBMS designed especially for objects.

Object-oriented DBMSs have an object query processor and an object kernel.

The Object Data Management Group (ODMG) provides the standard for object-oriented DBMSs.


Component Architecture for Component Architecture for Object-Oriented DBMSsObject-Oriented DBMSs

Database

Object query processor(parser, optimizer, display

manager)


OQL statementsand results

Relational kernel(transaction processing,

storage management, buffermanagement)


Summary of ArchitecturesSummary of Architectures Architecture Example Products Comments

Large objects Most SQL-92 DBMSs

Poor performance; no query language support; universal storage capability

Media servers Oracle 7.3 with text and spatial data servers

No query language support; poor performance involving simple and complex data; good performance on complex data

Object database middleware

Microsoft Universal Data Access

Uncertain performance when combining simple and complex data; Ability to combine diverse data sources

Object relational (SQL3)

IBM UniData Data Blades, IBM DB2 Extenders, Oracle 9i

Uncertain reliability; good query language support; some type mismatch with programming languages; good support with specialized storage structures

Object-oriented (ODMG)

ObjectStore, UniSQL, O2, Versant, Gemstone

Good query language support; uncertain performance for traditional applications; good type match with programming languages


Object Database Features in Object Database Features in SQL:1999SQL:1999Very large standardCore language partPackagesDetails about basic and enhanced object

supportTwo levels of conformance


SQL:1999 PackagesSQL:1999 Packages SQL3 Package Scope

Core SQL environment, SQL implementation, tables, views, predefined data types, SQL statements, conformance specifications

Persistent Stored Modules Computational completeness, stored modules, function overloading

Call Level Interface Call interface for SQL

Enhanced Datetime Facilities

Time zone specification, interval data type

Enhanced Integrity Management

Assertions, triggers, constraint management

OLAP Facilities Cube and roll-up operators, row and table constructors, FULL JOIN and INTERSECT operators

Basic Object Support User-defined data types, single inheritance, reference types, arrays

Enhanced Object Support Path expressions, subtable definition, subtable search, subtypes


User-Defined TypesUser-Defined Types Bundles data and proceduresSupport definition of structured types, not

just extensions of standard typesUser-defined types can be used as data types

for columns in tables, passed as parameters, and returned as values.

User-defined functions can be used in expressions in the SELECT, the WHERE, and the HAVING clauses.


User-Defined Type ExampleUser-Defined Type Example

Example 1: Point Type

CREATE TYPE Point AS ( x FLOAT, -- X coordinate y FLOAT ) -- Y coordinate METHOD Distance(P2 Point) RETURNS FLOAT, -- Computes the distance between 2 points METHOD Equals (P2 Point) RETURNS BOOLEAN -- Determines if 2 points are equivalent NOT FINAL INSTANTIABLE;


Explicit MethodsExplicit Methods

Return single values and use input parameters

Implicit first parameter: part of user-defined type

CREATE METHOD statement for method body

Mutation methods: change valuesProcedures and functions not associated

with types


Implicit MethodsImplicit Methods

Automatically exist for all user-defined types

Constructor method: creates an empty instance

Observer methods: retrieve valuesMutation methods: change values


User-Defined Type using an User-Defined Type using an ArrayArray

Example 2: Polygon type using an ARRAYCREATE TYPE Polygon AS( Corners Point ARRAY[10], Color INTEGER ) METHOD Area() RETURNS FLOAT, -- Computes the area METHOD Scale (Factor FLOAT) RETURNS Polygon -- Computes a new polygon scaled by factorNOT FINAL;


Table Definitions Table Definitions Traditional style: foreign keys to link

tablesTyped tables: supports object identifiers

and object referencesRow type constructor: supports rows as

variables and parameters


Example of table definition with Example of table definition with a row type a row type

Example 3: Property table definition with a row type

CREATE TABLE Property (PropNo INTEGER, Address ROW (Street VARCHAR(50), City VARCHAR(30), State CHAR(2), Zip CHAR(9) ), SqFt INTEGER, View BLOB, AgentNo INTEGER, Location Point, CONSTRAINT PropertyPK PRIMARY KEY(PropNo), CONSTRAINT AgentFK FOREIGN KEY(AgentNo) REFERENCES Agent );


Table Definition with a User-Table Definition with a User-Defined TypeDefined Type

Example 4: Definition of AgentType, followed by the Agent table based on AgentType

CREATE TYPE AddressType AS (Street VARCHAR(50), City VARCHAR(30), State CHAR(2), Zip CHAR(9) ) NOT FINAL; CREATE TYPE AgentType AS (AgentNo INTEGER, Name VARCHAR(30), Address AddressType, Phone CHAR(13), Email VARCHAR(50) ) NOT FINAL; CREATE TABLE Agent OF AgentType (REF IS AgentOId SYSTEM GENERATED, CONSTRAINT AgentPK PRIMARY KEY(AgentNo) );


Subtable FamiliesSubtable Families A table can be declared as a subtable of

another table. A subtable inherits the columns of its

parent tables.SQL:1999 limits inheritance for tables to

single inheritance. Set inclusion determines the relationship

of a table to its subtables.


Subtable ExampleSubtable ExampleExample 5: Subtable of Property Table

CREATE TYPE ResidentialType UNDER PropertyType (BedRooms INTEGER, BathRooms INTEGER, Assessments DECIMAL(9,2) ARRAY[6] ) NOT FINAL INSTANTIABLE; CREATE TABLE Residential OF ResidentialType UNDER Property; CREATE TYPE IndustrialType UNDER PropertyType (Zoning VARCHAR(20), AccessDesc VARCHAR(20), RailAvailable BOOLEAN, Parking VARCHAR(10) ) NOT FINAL INSTANTIABLE; CREATE TABLE Industrial OF IndustrialType UNDER Property;


Side effects when manipulating Side effects when manipulating rows in subtable familiesrows in subtable familiesOn insert into a subtable, a corresponding

row is inserted into each parent table.On update in a parent table, the column is

also updated in all direct and indirect subtables that inherit the column.

On update of an inherited column, the column is changed in the corresponding rows of direct and indirect parent tables.

On delete, every corresponding row in both parent and subtables is also deleted.


Manipulating Complex Objects Manipulating Complex Objects and Subtable Familiesand Subtable Families Path expressions to manipulate columns

with row references.References to methods in expressions

using the dot notation Testing membership in a specific table

without being a member of any subtables.


Using the ROW KeywordUsing the ROW KeywordExample 6: Using the ROW keyword in an INSERT statement.

INSERT INTO Agent (AgentNo, Name, Address, Email, Phone) VALUES (999999, 'Sue Smith', ROW('123 Any Street', 'Denver', 'CO', '80217'), '[email protected]', '13031234567') Example 7: Using a type name in an INSERT statement.

INSERT INTO Agent (AgentNo, Name, Address, Email, Phone) VALUES (999999, 'Sue Smith', AddressType('123 Any Street', 'Denver', 'CO', '80217'), '[email protected]', '13031234567');


Obtaining Object IdentifiersObtaining Object Identifiers

Example 8: Using a SELECT statement to retrieve the

object identifier of the related Agent row.

INSERT INTO Residential (PropNo, Address, SqFt, AgentRef, BedRooms, BathRooms, Assessments) SELECT 999999, AddressType('123 Any Street', 'Denver', 'CO', '80217'), 2000, AgentOID, 3, 2, ARRAY[190000, 200000] FROM Agent WHERE AgentNo = 999999;


Example of Example of path expression path expression versus traditional expressionversus traditional expression

Example 9: SELECT statement with path expressions and the

dereference operator

SELECT PropNo, P.Address.City, P.AgentRef->Address.City FROM Property P WHERE AgentRef->Name = 'John Smith'


Oracle 9i Object FeaturesOracle 9i Object Features

Supports most parts of the SQL:1999 object packages

User-defined typesTyped tablesOther object features


User-Defined Type ExampleUser-Defined Type ExampleExample 10: Point type in Oracle 9i

CREATE TYPE Point AS OBJECT ( x FLOAT(15), y FLOAT(15), MEMBER FUNCTION Distance(P2 Point) RETURN NUMBER, -- Computes the distance between 2 points MEMBER FUNCTION Equals (P2 Point) RETURN BOOLEAN, -- Determines if 2 points are equivalent MEMBER PROCEDURE Print ) NOT FINAL INSTANTIABLE;


InheritanceInheritanceExample 11: ColorPoint type in Oracle 9i

CREATE TYPE ColorPoint UNDER Point (Color INTEGER, MEMBER FUNCTION Brighten (Intensity INTEGER) RETURN INTEGER, -- Increases color intensity MEMBER FUNCTION Equals (CP2 ColorPoint) RETURN BOOLEAN, -- Overriding is not used because the two -- Equals methods have different signatures. OVERRIDING MEMBER PROCEDURE Print ) NOT FINAL INSTANTIABLE;


Typed TablesTyped TablesExample 12: Typed table example

CREATE TYPE PropertyType AS OBJECT (PropNo INTEGER, Address AddressType, SqFt INTEGER, AgentRef REF AgentType, Location Point ) NOT FINAL INSTANTIABLE; CREATE TABLE Property OF PropertyType ( CONSTRAINT PropertyPK PRIMARY KEY(PropNo), CONSTRAINT AgentRefFK FOREIGN KEY(AgentRef) REFERENCES Agent ) OBJECT IDENTIFIER IS SYSTEM GENERATED ;


Inheritance for Typed TablesInheritance for Typed TablesExample 13: Typed table example with inheritance

CREATE TYPE AssessType AS VARRAY(6) OF DECIMAL(9,2); CREATE TYPE ResidentialType UNDER PropertyType (BedRooms INTEGER, BathRooms INTEGER, Assessments AssessType ) NOT FINAL INSTANTIABLE; CREATE TABLE Residential OF ResidentialType (CONSTRAINT ResidentialPK PRIMARY KEY(PropNo), CONSTRAINT AgentRefFK1 FOREIGN KEY(AgentRef) REFERENCES Agent ) OBJECT IDENTIFIER IS SYSTEM GENERATED ;


Inserting into Typed TablesInserting into Typed TablesExample 14: Insert rows into the residential and property tables

INSERT INTO Residential (PropNo, Address, SqFt, AgentRef, BedRooms, BathRooms, Assessments) SELECT 999999, AddressType('123 Any Street', 'Denver', 'CO', '80217'), 2000, REF(A), 3, 2, AssessType(190000, 200000) FROM Agent A WHERE AgentNo = 999999; INSERT INTO Property (PropNo, Address, SqFt, AgentRef) SELECT 999999, AddressType('123 Any Street', 'Denver', 'CO', '80217'), 2000, REF(A) FROM Agent A WHERE AgentNo = 999999;


Path ExpressionsPath ExpressionsExample 15: Path expression using the DEREF function

SELECT PropNo, P.Address.City, DEREF(AgentRef).Address.City FROM Property P WHERE DEREF(AgentRef).Name = 'John Smith';

Example 16: Path expression using the dot operator

SELECT PropNo, P.Address.City, P.AgentRef.Address.City FROM Property P WHERE P.AgentRef.Name = 'John Smith';


Other Object FeaturesOther Object Features

Type substitutability for subtablesHierarchical viewsNested tables


SummarySummary

Three principles of object-oriented computing guide the development of object DBMSs.

A number of object DBMS architectures are commercially available.

SQL:1999 supports definition and manipulation of object relational databases.

Oracle 9i is a significant implementation of the SQL:1999 object packages

Documents

Chapter 18 Object Database Management Systems. McGraw-Hill/Irwin © 2004 The McGraw-Hill Companies, Inc. All rights reserved. Outline Motivation for object