FROM RELATIONAL TO OBJECT DATABASE MANAGEMENT SYSTEMS

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Christophides Vassilis 1

FROM RELATIONAL TO OBJECT DATABASE MANAGEMENT

SYSTEMS

V. CHRISTOPHIDES

Department of Computer Science & Engineering University of California, San Diego

ICS - FORTH, Heraklion, Crete

2 Spring 2000

Christophides Vassilis

I) INTRODUCTION

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What is a DBMS?

● Database: Logically coherent collection of “computerized” data

◆Stored Data: Persistent facts with some inherent meaning

◆Accessible Data: Extracted and derived facts for a specific purpose

● Database Management System: General purpose software that

facilitates the process of defining, constructing and manipulating database for various applications. It offers the following services:

◆Data Persistence

◆Disk Management

◆Data Sharing

◆Data Reliability

◆Ad hoc Queries

4 Spring 2000

DBMS Applications

● Administration & Management

◆Bank Accounts

◆Company Stocks & Personal

◆Airline Reservation

◆University Courses and Notes

◆Library Books Borrowing

● Media & Net-centric Applications

◆Engineering (CAD/CAM/CIM/CAE)

◆Scientific Applications

•Genome Databases, Environmental Applications (GIS)

◆Telecommunications + Databases

•Network management, Tele- medicine, Info Brokering

◆Multimedia, Entertain., Visualization

•Interactive, Virtual Reality based

◆Software Design and Management

◆Data Warehouses

◆Web Site Management

◆Electronic Commerce

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DBMS vs. other types of software

● Effective Manipulation of Persistent Data

◆recovery from failures

◆concurrent access

◆security & integrity controls

◆data independence physical & logical & user

● Efficient Access to Large Data Volumes

◆buffer management

◆indexing/clustering

◆query optimization

◆distribution

6 Spring 2000

Example: Phone Directory

● One file:

•first and last name, address, profession, telephone number

● Two type of access:

•Direct by first/last name (white pages)

•Sequential by profession headings (yellow pages)

● Implementation without a DBMS:

•Hashing on first/last name (key) and linked lists of profession headings

•Change of the access mode implies PROGRAM RERWITING

● Implementation with a DBMS:

•Choice of a physical structure

•Choice of a logical structure

•Application programs are build on the top of data logical structuring

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The ANSI-SPARC Architecture

● External Level:

◆What actually seen by users (not necessary the whole database)

● Conceptual Level:

◆Modeling of the real-word data, independent from the underlying DBMS

● Internal Level: How data is physically stored

◆Logical-schema: Logical organization of data using the DBMS data model (tables, etc.)

◆Physical-schema: Physical organization of data in the secondary memory (files, records, etc.)

➲The ability to modify a scheme definition in one level without affecting a scheme definition in a higher level is called data independence

8 Spring 2000

Three Level Architecture

PHYSICAL SCHEMA LOGICAL SCHEMA

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VIEW 1 VIEW 2 VIEW 3

INTEGRATION

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The Data Independence issue

● Physical (for optimization)

•Changes of physical structures doesn’t affect data logical organization

•EXAMPLE: Addition/Suppression of indices in a DBMS

● Logical (for maintainability)

•Modifications of data logical structure should not affect programs

•EXAMPLE: New Relations/Attributes in the logical schema of a DBMS

● User (for flexibility)

•Multiple views on the same logical organization of data

•EXAMPLE: Secretary and Professor views on a University database

✔Data independence is achieved by inter-level mappings

✔Queries are translated between levels automatically

10 Spring 2000

Mappings in DBMS

Strorage structure definition (Internal Schema) Conceptual View

Conceptual/

Internal Mapping External View A

Conceptual/

External Mapping A

Stored database (internal View) Host Language + DSL Host Language + DSL

User A User B

External Schema A

Conceptual Schema

Database Management Systems (DBMS)

Schemas and mapping built and maintained by the database administrator (DBA)

USER INTERFACE

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DBMS Components

● Data Collections:

•Minimizing data redundancy

•Enabling multi-user access

● People:

•Database Designer

•Database Administrator

•Application Programmers

•End-Users

● Hardware:

•Processor(s)

•Main Memory

•Secondary Storage (e.g., disks, CD-ROMs, etc.)

● Software

•The Storage Manager:

buffer and file manager

•The Transaction Manager:

locking, logging, and transaction commitment (ACID)

•The Query Processor:

parsing, optimization, execution

•Various Automated Tools:

Development and Design aids, Report writers, etc.

12 Spring 2000

Typical Architecture of a DBMS

Schema Modifications

Data

Modifications Queries

“Query” Processor

Storage Manager

Transaction Manager

Data & Metadata

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Application Development: Backend vs. Frontend

● Backend ➙ the DBMS

● Frontends ➙ Applications which run on top of the DBMS

● Examples of vendor-provided applications or tools

•Query language processor

•Business graphics sub-systems

•Spreadsheet

•Statistical packages

•Application generators

•CASE Tools

•Report writer

•Web-DBMS Gateways

● Examples of typical utilities to help DBAs in various tasks

•Load routines

•Unload/Reload routines

•Reorganization routines

•Statistic routines

•Analysis routines

Database End User

Frontend

Backend

Applications

Programming Interface

DBMS

14 Spring 2000

Application Development: Client/Server Architecture

Database End User

Frontend

Backend

Applications

DBMS Transparent remote

access

● Partition of programs between client et server processes, communicating via queries

● Hierarchical partition of functions

◆data at the servers are shared by several clients

◆graphical interfaces at the end- user workstations

◆communication through standardized protocols

◆distribution of application programs in order to minimize transfer costs

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Client/Server Architecture: First Generation

Windows NT UNIX

CLIENTS APPLICATIONS

Queries Results

rules DBMS

NT, UNIX, NOVELL GCOS, VMS, MVS

APPLICATIONS SERVER

APPLICATION

Data

 G. Gardarin

16 Spring 2000

Client/Server Architecture: Second Generation

Application Application Tool Connectivity Tool Network Protocol

DB Server

Database CLIENTS

Service Requests

Results

SERVER

Network Protocol Connectivity Tool Stored

Procedures

● Stored Procedures

◆Procedure accomplice a service function on data

● Service-oriented architecture rather than query-oriented

◆Distribution of data manipulation

● Extensibility and Scalability

◆Possibility to have several, eventually redundant, servers

◆Possibility to have private data on clients

Application Application Tool Connectivity Tool Network Protocol

Service Requests

 G. Gardarin

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Client/Server Architecture: Third Generation

● Integration of the Web with the client-server

◆Use Web browsers for a standard presentation to the client

◆Possibility to run small client application (applets)

◆Significant portability (Virtual Private Network, Intranet, Internet)

● Three(or Multi)-tiered Architectures

◆Databases with stored procedures

◆Shared application services

● Hypermedia support

◆Various media types which can be extended (text, image, video)

◆Navigation between documents and applications

Oracle Oracle Database Database

URL HTML

WRB WRB WRBWRB WRBWRB WRB WRB WRB

Web Request Broker WRB

Cartridges

Web Request Broker HTTP

Server

Files or CGI

PL/SQL C Java Perl JCORBA

Browser

 ORACLE

18 Spring 2000

Database Technology Timeline

Early 80s Late 80s Early - Mid 90s Late 90s - 21st C

Pre- relational

Early Relational

Client-server Relational

Enterprise -capable Relational

Internet Computing

Simple OLTP

Active Database

Data Warehouse &

Hi-end OLTP

Packaged &

Vertical Applications

Simple transactions,

on-line backup &

recovery

Stored procedures,

triggers

Scaleable OLTP, parallel query,

partitioning, cluster support, row-level locking,

high availability

Middleware (messaging, queues,events)

Java, CORBA, Web interfaces Support for

all types of data, extensibility,

objects Simple Data

Management

Global Enterprise Management