modern’ databases software

8/2/2019 Modern Databases Software

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Modern Databases Software

Mahesh Bane


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'Modern' Databases

In This Lecture

'Modern' Databases

Distributed DBs

Web-based DBs Object Oriented DBs

Semistructured Data and XML

Multimedia DBs

For more information

Connolly and Begg chapters 22-28

Ullman and Widom chapter 4


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'Modern' Databases

Other Sorts of DB

We have lookedmainly at relationaldatabases

Relational model

SQL

Design techniques

Transactions

Many of these topicsrelied on relationalconcepts

There are severalother types of DB inuse today

Distributed DBs

Object DBs

Multimedia DBs

Temporal DBs

Logic DBs


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'Modern' Databases

Distributed Databases

A distributed DBsystem consists ofseveral sites

Sites are connectedby a network

Each site can holddata and process it

It shouldnt matterwhere the data is -the system is a singleentity

Distributed databasemanagement system(DDBMS)

A DBMS (or set ofthem) to control thedatabases

Communicationsoftware to handleinteraction betweensites


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'Modern' Databases

Client/Server Architecture

The client/serverarchitecture is ageneral model for

systems where aservice is provided byone system (theserver) to another

(the client)

Server

Hosts the DBMS anddatabase

Stores the data

Client

User programs thatuse the database

Use the server fordatabase access


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'Modern' Databases

Distributed Databases

Network

Client(s)

Server

Client(s)

Server

Client(s)

Server

Client(s)

Server

Client(s)

Server


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'Modern' Databases

Web-based Databases

Database access overthe internet

Web-based clients

Web server

Database server(s)

Web server servespages to browsers

(clients) and canaccess database(s)

Typical operation

Client sends a requestfor a page to the web

server Web server sends SQL

to database

The web server usesresults to create page

The page is returned tothe client


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'Modern' Databases

Web-based Databases

Client

(Browser)

Web

Server

Database

Server

HTTP request

SQL query

SQL result

HTML page


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'Modern' Databases

Web-based Databases

Advantages

World-wide access

Internet protocols

(HTTP, SSL, etc) giveuniform access andsecurity

Database structure ishidden from clients

Uses a familiarinterface

Disadvantages

Security can be aproblem if you are not

careful Interface is less

flexible usingstandard browsers

Limited interactivity

over slow connections


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'Modern' Databases

Object Oriented Databases

Relational DBs

The database cantsee datas internal

structure so cant usecomplex data

Relational modelgives a simple, andquite powerful,

structure - but isquite rigid

Object Oriented DBs

Use concepts fromobject oriented

design/programming OO concepts

Encapsulation

Inheritance

Polymoprhism

OODBMS


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'Modern' Databases


An object orienteddatabase (OODB) is acollection of

persistent objects Objects - instances of

a defined class

Persistent - object

exist independently ofany program

An object orientedDBMS

Manages a collection

of objects

Allows objects to bemade persistent

Permits queries to bemade of the objects

Does all the normalDBMS things as well


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'Modern' Databases

OODB example

In lecture 10 we hada store with differentsorts of products

Books

CDs

DVDs

This lead to missing

data among thevarious types

OODB solution

We make an abstractProduct class

Book, CD, and DVDare each a concretesubclass of Product

The database is apersistent collection

of Products


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'Modern' Databases

OODB Example

Product is abstract

You cannot make aProduct directly

You can, however,make a Book, CD, orDVD, and these areProducts

Product

Book CD DVD

Price

Title

Shipping

Author

Publisher

Artist Producer

Director


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'Modern' Databases


Advantages

Good integration withJava, C++, etc

Can store complexinformation

Fast to recover wholeobjects

Has the advantages ofthe (familiar) objectparadigm

Disadvantages

There is no underlyingtheory to match the

relational model Can be more complex

and less efficient

OODB queries tend tobe procedural, unlike

SQL


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'Modern' Databases

Object Relational Databases

Extend a RDBMS withobject concepts

Data values can be

objects of arbitrarycomplexity

These objects haveinheritance etc.

You can query the

objects as well as thetables

An object relationaldatabase

Retains most of the

structure of therelational model

Needs extensions toquery languages (SQLor relational algebra)


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'Modern' Databases

Semistructured data

Semistructured Data: A new data modeldesigned to cope with problems ofinformation integration.

XML : A standard language for describingsemistructured data schemas andrepresenting data.


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'Modern' Databases

The Information-Integration

Problem Related data exists in many places and could, in

principle, work together.

But different databases differ in:

Model (relational, object-oriented?).

Schema (normalised/ not normalized?).

Terminology: are consultants employees?Retirees? Subcontractors?

Conventions (meters versus feet?).

How do we model information residing inheterogeneous sources (if we cannot combine it all ina single new database)?


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'Modern' Databases

Example

Suppose we are integrating information about bars insome town.

Every bar has a database.

One may use a relational DBMS; another keeps themenu in an MS-Word document.

One stores the phones of distributors, another doesnot.

One distinguishes ales from other beers, another

doesnt. One counts beer inventory by bottles, another by

cases.


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'Modern' Databases

Semistructured Data

Purpose: represent data from independent sourcesmore flexibly than either relational or object-orientedmodels.

Think of objects, but with the type of each object its

own business, not that of its class. Labels to indicate meaning of substructures.

Data is self-describing: structural information is part ofthe data.


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'Modern' Databases

Graphs of Semistructured

Data Nodes = objects.

Labels on arcs (attributes, relationships).

Atomic values at leaf nodes (nodes with no arcs out).

Flexibility: no restriction on:

Labels out of a node.

Number of successors with a given label.


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'Modern' Databases

Example: Data Graph

Bud

A.B.

Gold1995

MapleJoes

Mlob

beer beerbar

manfmanf

servedAt

name

namename

addr

prize

year award

root

The bar objectfor Joes Bar

The beer objectfor Bud

Notice anew kindof data.


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'Modern' Databases

XML

XML = Extensible Markup Language.

While HTML uses tags for formatting (e.g., italic), XMLuses tags for semantics (e.g., this is an address).

Key idea: create tag sets for a domain (e.g., bars), andtranslate all data into properly tagged XML documents.

Well formed XML - XML which is syntactically correct;tags and their nesting totally arbitrary.

Valid XML - XML which has DTD (document type

definition); imposes some structure on the tags, butmuch more flexible than relational database schema.


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'Modern' Databases

XML and Semistructured

Data Well-Formed XML with nested tags is exactly the same

idea as trees of semistructured data.

XML also enables non-tree structures (with references

to IDs of nodes), as does the semistructured datamodel.


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'Modern' Databases

Example: Well-Formed XML

Joes Bar

Bud2.50

Miller

3.00


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'Modern' Databases

Example

The XML document is:

Joes Bar

Bud 2.50 Miller 3.00

PRICE

BAR

BAR

BARS

NAME . . .

BAR

PRICENAME

BEERBEER

NAME


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'Modern' Databases

XPATH and XQUERY

XPATH is a language for describing paths in XMLdocuments.

Really think of the semistructured data graph and its

paths. Why do we need path description language: cant

get at the data using just Relation.Attributeexpressions.

XQUERY is a full query language for XML documents

with power similar to OQL (Object Query Language,query language for object-oriented databases).


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'Modern' Databases

Multimedia Databases

Multimedia DBs canstore complexinformation

Images

Music and audio

Video and animation

Full texts of books

Web pages

They can be used ina wide range ofapplication areas

Entertainment

Marketing

Medical imaging

Digital publishing

GeographicInformation Systems


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'Modern' Databases

Querying Multimedia DBs

Metadata searches

Information about themultimedia data

(metadata) is stored This can be kept in a

standard relationaldatabase and queriednormally

Limited by theamount of metadataavailable

Content searches

The multimedia datais searched directly

Potential for muchmore flexible search

Depends on the typeof data being used

Often difficult to

determine what thecorrect results are


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'Modern' Databases

Metadata Searches

Example - indexingfilms we might store

Title

Year

Genre(s)

Actor(s)

Director(s)

Producer(s)

We can then searchfor things like

Films starring Kevin

Spacey Films directed by

Peter Jackson

Dramas produced in2000

We dont actuallysearch the films


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'Modern' Databases

Metadata Searches

Advantages

Metadata can bestructured in a

traditional DBMS Metadata is generally

concise and soefficient to store

Metadata enriches the

content

Disadvantages

Metadata cant alwaysbe found

automatically, and sorequires data entry

It restricts the sortsof queries that can bemade


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'Modern' Databases

Content Searches

An alternative tometadata is to searchthe content directly

Multimedia is lessstructured thanmetadata

It is a richer source ofinformation but

harder to process

Example of contentbased retrieval

Find images similar to

a given sample Hum a tune and find

out what it is

Search for features,such as cuts or

transitions in films


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'Modern' Databases

Content-Based Retrieval

QBIC (Query By Image Content)

from IBM - searches for images

having similar colour or layout

http://wwwqbic.almaden.ibm.com/cgi-bin/stamps-demo


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'Modern' Databases

Content-Based Retrieval

Image retrieval ishard

It is often not clear

when two images aresimilar

Image interpretationis unsolved andexpensive

Different peopleexpect differentthings

Do we look for?

Images of roses

Images of red things?

Images of flowers?

Images of red flowers?

Images of red roses?


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'Modern' Databases

Other Topics

Temporal DBs

Storing data thatchanges over time

Can ask about thehistory of the DBrather than just thecurrent state

System time vs real

time

Logic DBs

A database is a set offacts and rules for

manipulating them(like a Prologprogram)

The DBMS maintainsand controls these

facts and rules A query is made by

applying the rules tothe facts

modern’ databases software

Documents