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ata ase ystem oncepts

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Outline

File-based Approach

Database Approach Database Systems

Roles in the Database Environment

DBMSs

ree- c ema rc ec ure an a a n epen ence

Database Languages

Data Models, Database Schema and Database State

Data Management Systems Framework Where are we?

Extending database capabilities for new applications

Reading Suggestion: [1,2]: Chapters 1, 2

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File-based Approach

Data is stored in one or more separate computer

Data is then processed by computer programs -

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File-based Approach

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File-based Approach

Problems/Limitations

Data Inconsistency

More details: see 2

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C u s to m e r

F i l e s

Files

File-based approach

C u s t o m e r

O r d e r s

F i l e

S t o c k

F i l e

A p p li c a t io n s

pplications

Customer

Customer

File

C u s to m e r

F i l e

r e r

F i l e Orders

Stock

File

C u s t o m e r

I n v o ic i n g

O r d e r

F i l e

S t o c k

F i l e

OrderFile

ustomer

Invoicing

P u r c h a s e

O r d e r s

S t o c k

F i l e

Purchase

OrdersSupplier

F i l e

S t o c k

C o n t r o l

S t o c k

F i l eStock

Control

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O r d e r

F i l eShared file approach

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File-based Approach

Shared File Approach Data (files) is shared between different applications

Data redundancy problem is alleviated Data inconsistency problem across different versions ofthe same file is solved

Other problems:Rigid data structure: If applications have to share files, the file structure that suits

one application might not suit another

some way, this alteration will need to be reflected in all application programs thatuse that data file

No support of concurrency control: While a data file is being processed by oneapplication, the file will not be available for other applications or for ad hoc queries

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Outline

FileFileFile---based Approachbased Approachbased Approach

Database Approach Database Systems


DBMSs


Database Languages

Data Models, Database Schema and Database State Data Management Systems Framework

Where are we?



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Database Approach

Arose because: ,

rather than being stored separately and independently No control over access and manipulation of data beyond

Result: The Database and Database Mana ement S stem

(DBMS).

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Database Approach

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Database Approach

Data

meaning Information? Knowledge?

ore: www.w a s.com

Database: Shared collection of logically related data,

information needs of an organization

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Database Approach

System catalog (metadata) provides description of data toenable programdata independence

og ca y re a e a a compr ses en es, a r u es, an

relationships of an organizations information DataBase Management System (DBMS): a general-purpose

so ware sys em a ac a es e processes o e n ng,constructing, manipulating, and sharing databases among

various users and applications (or a software system that, , ,to the database)

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Database Approach

Data Definition Language (DDL) Permits specification of data types, structures and any data constraints to be

stored in the database

All specifications are stored in the database

Data manipulation language (DML). Query language: retrieve (query), update (insert, delete, modify)

ontro e access to ata ase may nc u e: a security system

an integrity system

a recovery control system

a user-accessible catalog

Database System = the Database + DBMS software

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Database Approach


Database Administrator DBA : res onsible for authorizin access to

DB, coordinating & monitoring its use, and for acquiring software and

hardware resources as needed

Database Desi ners: res onsible for identif in the data to be stored

in DB, choosing appropriate structures to represent and store this

data

A lication Pro rammers

End Users

More details: see [1,2]-chapter 1

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Database Approach

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Database Approach

Characteristics of the Database Approach Self-describing nature of a database system

Insulation between programs and data, and data abstraction

Program-data independence + Program-operation independence = Dataabstraction

a a mo e s a ype o a a a s rac on

Support of multiple views of the data

Sharing of data and multi-user transaction processing er a van ages o us ng e approac : see - .

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Database Approach

History of database systems

Second generation: Relational

Third eneration: Ob ect-Relational Ob ect-Oriented

Brief history of database applications

see 1 -section 1.7

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Example of Network Model Schema

Slide 2- 18

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Example of Relational Model Schema

Slide 1- 19

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Outline


Database ApproachDatabase ApproachDatabase Approach Database SystemsDatabase SystemsDatabase Systems

Roles in the Database EnvironmentRoles in the Database EnvironmentRoles in the Database Environment DBMSsDBMSsDBMSs


Database Languages


Where are we?



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Three-Schema Architecture and Data

Inde endence Objectives of Three-Schema Architecture

Users should not need to know physical database storagedetails

s ou e a e o c ange a a ase s oragestructures without affecting the users views

Internal structure of database should be unaffected bychanges to physical aspects of storage

DBA should be able to change conceptual structure ofdatabase without affectin all users

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Inde endence Three-level architecture and data independence

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Inde endence External Level

Describes that part of database that is relevant to aparticular user

Conceptual Level

Community view of the database Describes what data is stored in database and

relationships among the data

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Inde endence Internal Level

.

Describes how the data is stored in the database

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Inde endence

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Inde endence Data Independence is the capacity to change the

having to change the schema at the next higherlevel

Logical Data Independence

Refers to immunity of external schemas to changes inconceptual schema

Conceptual schema changes (e.g. addition/removal of

or rewrites of application programs

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Inde endence Physical Data Independence

the internal schema Internal schema changes (e.g. using different file

organizations, storage structures/devices) should not

require changes to conceptual or external schemas

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Inde endence

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Outline




reereeree--- c ema rc ec ure an a a n epen encec ema rc ec ure an a a n epen encec ema rc ec ure an a a n epen ence

Database Languages


Where are we?



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Database Languages

Data Definition Language (DDL) allows the DBA or user todescribe and name entities, attributes, and relationships

security constraints Data Manipulation Language (DML) provides basic data

Data Control Language (DCL) defines activities that are not

in the categories of those for the DDL and DML, such as,changes to a databases should be irrevocably made

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Database Languages

Procedural DML allows user to tell system exactlyhow to manipulate data (e.g., Network and

erarc ca s

Non-Procedural DML (declarative language) allows

is to be retrieved (e.g., SQL, QBE)

Fourth Generation Languages (4GLs) on-proce ura anguages: , , e c. Application generators, report generators, etc. (see [2])

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Outline





Database LanguagesDatabase LanguagesDatabase Languages


Where are we?



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D t M d l D t b S h d

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Data Models, Database Schema andDatabase State

Data Model: An integrated collection of concepts fordescribing data, relationships between data, and constraints

Categories of data models include: Object-based (Conceptual)

Describe data at , - ,

Record-based (Representational)Relational, Network, Hierarchical

the conceptual &

external levels

Physical: used to describe data at the internal level

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D t M d l D t b S h d

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Data Models, Database Schema andDatabase State

Database Schema: the description of a database,

expected to change frequently

Database State (Snapshot): the data in the

database at a articular moment in time

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Outline





Database LanguagesDatabase LanguagesDatabase Languages

Data Models, Database Schema and Database StateData Models, Database Schema and Database StateData Models, Database Schema and Database State Data Management Systems Framework

Where are we?



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Data Management Systems Framework

Where are we?

Visualization, Collaborative Computing, Mobile Computing,

Knowledge-based Systems

Application

Layer

Data Warehousing, Data Mining, Internet DBs, Collaborative, P2P &

Grid Data Management

La er 2: intero erabilit & mi ration

Data

ManagementHeterogeneous DB Systems, Client/Server DBs, Multimedia DB

Systems, Migrating Legacy DBs

Layer 1: DB technologies

ayer

DB Systems, Distributed DB SystemsNetworking, Mass Storage, Agents, Grid Computing Infrastructure,

Parallel & Distributed Processing, Distributed Object ManagementSupporting

La er

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Data Management Systems Framework


Exam le a lications: stora e and retrieval of ima es videos data

mining (large amounts of data need to be stored and analyzed),

spatial databases, time series applications,

More com lex data structures than relational re resentation

New data types except for the basic numeric and character string

types

New storage and retrieval methods

New security mechanisms

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Summary

File-based Approach

Three-Schema Architecture and DataInde endence

Database Languages

Data Models Database Schema and DatabaseState

Data Management Systems Framework (where are

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Q&A

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Documents

lec1-MT07