Object-Oriented DatabasesOriented Databases · Object-Relational Databases Relational model...

Object-Oriented DatabasesObject Oriented DatabasesIntroduction

• Course Overview• Evolution and History of Database Management Systems• Requirements of Object-Oriented Database Management Systems

September 19, 2008 1Michael Grossniklaus – Department of Computer Science – [email protected]

Organisation

Michael GrossniklausETH Z i h P lit i di MilETH Zurich Politecnico di MilanoIFW D 46.2 Campus Bassini, Room 18/103+41 44 632 72 73 +39 022 399 3474+41 44 632 72 73 +39 022 399 [email protected] [email protected]

Alexandre de SpindlerETH ZurichIFW D 47.1

41 44 632 74 16+41 44 632 74 [email protected]


Exercises

Course will be accompanied by exercisesWork with technologies covered in the courseTutorial sessions every week

Starting on October 3rd, 2008IFW A 32.1, 11-12Al d d S i dlAlexandre de Spindler

Optional but strongly recommended!Optional, but strongly recommended!


Exam

Session examinationJ 19th 2009 F b 13th 2009January 19th, 2009 – February 13th, 2009Exceptions can be arranged for exchange students

Oral exam in EnglishOral exam in EnglishDuration of 15 minutes5 ECTS


Course Overview

I. Basics of Object-Oriented Databases1 I t d ti1. Introduction2. Object Persistence3 db4o3. db4o

II. Advanced Concepts of Object-Oriented Databases4 Standards and Commercial Systems4. Standards and Commercial Systems5. Storage and Indexing6. Version Models

III. Semantic Object Data Management7. OM Data Model and OM Data Model Languageg g8. Design and Implementation of OMS Avon9. Context-Aware Data Management


Database Design

Conceptual Design

Implementation Design

Physical Design

6September 19, 2008 Michael Grossniklaus – Department of Computer Science – [email protected]

Database Management Systems

Conceptual modellingClient Interface Layer E/R

SQL, JDBC, ODBC

Conceptual modelling Data access and representation

Data Model Layer Relational ModelData semanticsOperation semantics

Storage Layer RDBMSPersistenceACIDDistribution


Evolution and History

Mod

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Mod

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Rel

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nal D

ata

Ent

ity-R

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ions

SQ

L:19

99X

ML

CO

DAS

YL

Sta

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OD

MG

1.0

OM

Dat

a M

odel

SQ

L-86

OD

MG

3.0

SQ

LHierarchical

Network

R E S XC O OS OS

Network

Object-Oriented

Relational

Object Oriented

Semi-Structured

Object-Relational

XML

1960 1970 1980 1990 20001960 1970 1980 1990 2000


Hierarchical Databases

Data organised in a treet h hilda parent can have many children

a child can have only one parent

Records described by entity typesRecords described by entity types1:N (one-to-many) relationshipsQuery by path navigationExamples

File systemLDAPWi d R i t d A ti Di tWindows Registry and Active DirectoryXML documents and XQuery


Network Databases

Data organised in graph (lattice)t h hilda parent can have many children

a child can have many parents

Bachmann diagramsBachmann diagramsRecord types define propertiesSet types defined relationships

parent-child, (double) linked list, …

Query by graph navigationExamples

CODASYL


Relational Databases

Data organised as tuples in relationsLink between data tuples

primary and foreign keys

Relational algebraproject, select, join

Relational normal formsDeclarative language

data definition, consistency, manipulation and querying

ExamplesOracle 11g, Microsoft SQL Server, IBM DB2PostgreSQL, MySQL


Relational Databases

Relational model is very simplel b i t f d t b i l t donly basic concepts → references need to be simulated

restricted type system → no user-defined types

Lack of semantic modellingLack of semantic modellingcomplex data, versioning, roles

Little support for data and schema evolutionLittle support for data and schema evolutionObject-relational impedance mismatch


Object-Relational Impedance MismatchObject Relational Impedance Mismatch

Object-oriented application development and relational j pp pdata management results in clash of two incompatible modelsCode to map between models is considerable overhead, costly and hard to maintaincostly and hard to maintain


Object-Oriented Databases

Data represented as objectsbj t id titobject identity

attributes and methodsreferences relationships associationsreferences, relationships, associations

Extensible type hierarchyuser-defined types abstract data typesuser defined types, abstract data typessingle or multiple inheritanceoverloading, overriding, late binding

Declarative language for ad hoc purposesBinding for object-oriented programming languageBinding for object oriented programming language


Object-Relational Databases

Relational model extendedt d l tinested relations

referencessetssetsrow types, abstract typesfunctions

Declarative language extendedcomputationally complete

Fundamental impedance mismatch remainsCommingling of modelsCommingling of models


Object-Relational Databases

create type AddressType (street varchar(10),city varchar(10)

)

create row type PublicationType (title varchar(50)

)

create row type BookType (isbn varchar(10)

) under PublicationType

create row type AuthorType (name varchar(25),books setof(BookType),address AddressType

))

create table Book of type BookTypecreate table Author of type AuthorType


Emerging and Future Databases

XML DatabasesC 251 0317 00LCourse 251-0317-00LXML and DatabasesProf. Dr. Donald Kossmann, Dr. Peter FischerAutumn Semester, Wed 13-15

Mobile and Personal DatabasesCourse 251-0373-00LMobile and Personal Information SystemsProf. Dr. Moira C. NorrieAutumn Semester Thu 9 11Autumn Semester, Thu 9-11


Object-Oriented DatabasesObject Oriented Databases

Object-OrientedSystems

DatabaseSystemsO

DB

Systems Systems

OO

Avoid object-relational impedance mismatchj pProvide a uniform data modelCombine features and properties ofCombine features and properties of

object-oriented systems and languagesdatabase management systemsdatabase management systems


Defining Object-Oriented Databases

Diverse focus of object-oriented database systemski bj t i t d i l i t tmaking object-oriented programming languages persistent

managing and storing object data

Many attempts to define object oriented databasesMany attempts to define object-oriented databasesThe object-oriented database manifesto

13 d t f t13 mandatory features5 optional characteristics4 open choices4 open choices

Manifesto aftermathseveral refutations from the relational campseveral refutations from the relational campseveral important properties not addressed


The Object-Oriented Database Manifesto

1. Complex objects2. Object identity 3. Encapsulation4 Types and classesObject oriented 4. Types and classes5. Type and class hierarchies6 Overriding overloading and late binding

Object-oriented systems

6. Overriding, overloading and late binding 7. Computational completeness8. Extensibility9. Persistence10. Efficiency11 CDatabase 11. Concurrency12. Reliability13 Declarative query language

Database management systems

13. Declarative query language


Objects

Complex objectsl bj t f d f i l b t tcomplex object formed from simpler ones by constructors

record, set, bag, list and array complex object constructorsconstructor orthogonalityconstructor orthogonality

Object identity and equalityevery object has unique and immutable object identifier (OID)every object has unique and immutable object identifier (OID)sharing of objects through referencestwo objects are identical if they have the same OIDtwo objects are equal if they have the same stateshallow and deep equality


Objects

Encapsulationbj t i t f i t f d i l t tiobject consists of interface and implementation

interface defines signatures of public methodsimplementation includes object data and methodsimplementation includes object data and methodsobject state is only modified through public methodsobject data structure may be exposed for declarative queries

record t perecord type

set type

publicinterface

set type


Types and Classes

Data typesd fi iti f bj t tidefinition of object propertiesstatic part describes object structuredynamic part describes object behaviourdynamic part describes object behaviourseparation of interface and implementationused to check correctness of programs at compile time

Object classescontainer for objects of the same typeobjects can be added and removedused to create and manipulate objects at run time


Types and Classes

Class Typehas

describescontains

Object Valuehas


Generalisation Hierarchies

Advantagesf l d lli t l +getName()

Publication

powerful modelling toolguarantee semantic complexityreuse of specification and implementation

+getName()+getAuthors()

A ti l B kreuse of specification and implementation

Inheritanceobjects of subclass belong automatically to superclass

+getPages()+getJournal()

Article

getISBN()

Book

objects of subclass belong automatically to superclassattributes and methods are inherited from superclasssubclass can introduce new attributes and methods

getConference()

Proceeding

Migration between classesmove objects between hierarchy levelsj yobject specialisation (↓) and generalisation (↑)class instance versus class member


Generalisation Hierarchies

Substitution inheritancebt h ti th tsubtype has more operations than supertype

subtype can be substituted where supertype is expectedbased on behaviour rather than valuesbased on behaviour rather than values

Inclusion inheritanceevery object of subtype is also object of supertypeevery object of subtype is also object of supertypebased on structure rather than operations

Constraint inheritanceConstraint inheritancespecial case of inclusion inheritancesubtype is expressed by constraint on supertypeyp p y p yp

Specialisation inheritancesubtype objects contain more specific informationyp j p


Overriding, Overloading and Late Binding

Method overridingth d i d fi d i bt

«interface»Shape

method is redefined in subtypeguarantees specialisation of methodspreserves uniform method interface

+draw(Graphics g)

Rectanglepreserves uniform method interface

Method overloadingeffect caused by method overriding

+draw(Graphics g)

Rectangle

effect caused by method overridingvarious version of a method can exist in parallel

Late binding+draw(Graphics g)

FilledRectangle

Late bindingappropriate version of overloaded method selected at run timealso known as virtual method dispatchingp g


Computational Completeness and Extensibility

Computational completenessi t f th th d i l t ti lrequirement for the method implementation language

any computable function can be expressedcan be realised through connection with existing languagecan be realised through connection with existing language

Extensibilitydatabase has a set of predefined typesdatabase has a set of predefined typesdevelopers can define new types according to requirementsno usage distinction between system and user types


Durability and Efficiency

Persistenced t h t i th tidata has to survive the program executionorthogonal persistenceimplicit persistenceimplicit persistence

Secondary storage managementindex managementindex managementdata clusteringdata bufferingaccess path selectionquery optimisation


Concurrency Control and Recovery

Concurrencyt f lti l tl i t timanagement of multiple users concurrently interacting

atomicity, consistency, isolation and durabilityserialisability of operationsserialisability of operations

Reliabilityresiliency to user software and hardware failuresresiliency to user, software and hardware failurestransactions can be committed or abortedrestore previous coherent state of dataredoing and undoing of transactionslogging of operations


Declarative Query Language

High-level languaget i i l i i lexpress non-trivial queries concisely

text-based or graphical interfacedeclarativedeclarative

Efficient executionpossibility for query optimisationpossibility for query optimisation

Application independentwork on any possible databasework on any possible databaseno need for additional methods on user-defined types


Optional Characteristics and Open Choices

Optional characteristicslti l i h itmultiple inheritance

type checking and inferencedistributiondistributiondesign transactions, long transactions, nested transactionsversions

Open choicesprogramming paradigmrepresentation systemtype system

if ituniformity


Beyond the Manifesto

Database administration utilitiesView definition and derived dataObject roles

objects have roles in addition to typesroles can be gained and lost dynamically

Database evolutionschema and data has to evolve gracefully over time

Constraintsintegrity, semantic and evolution constraintsd fi iti t d f t f t i tdefinition, management and enforcement of constraints


Literature

M. Atkinson, F. Bancilhon, D. DeWitt, K. Dittrich, D. Maier, d S Zd ik Th Obj t O i t d D t b S tand S. Zdonik: The Object-Oriented Database System

Manifesto, In: Building an Object-Oriented Database System Morgan Kaufmann 1992System, Morgan Kaufmann 1992M. Stonebraker, L. A. Rowe, B. Lindsay, J. Gray, M. Carey, M B di P B t i d D B h Thi d G tiM. Brodie, P. Bernstein, and D. Beech: Third-Generation Database System Manifesto, In: ACM SIGMOD RECORD 19(3) 1990RECORD, 19(3), 1990H. Darwen and C. J. Date: The Third Manifesto, In: ACM SIGMOD RECORD 24(1) 1995SIGMOD RECORD, 24(1), 1995


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• Serialisation• Object-Relational Mappings and Frameworks• Persistent Programming Languages


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