web services & related technologies

8/3/2019 Web Services & Related Technologies

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Web Services &

RelatedTechnologies XML

UDDI

WSDL

SOAP

Bit torrent

Napster

Freenet

Gnutella

By:

Deepika Nair1


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Web Services What?A web service is a software system that:

}

Supports interoperable machine to machinecommunication over a network

} Has an interface defined in a machineprocessable format (WSDL)

} Interaction with the web service possible usingSOAP.

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Web services Why? -I

} Enable systematic interactions between

applications irrespective of the platform and

language of implementation.

} Easy reuse of existing code

} Open Standards

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Web services Why? -II

} Dynamic Integration

} Easier distribution of application to more number of

customers

} Rapid development

} Can work in the Internet as well as more

constrained environments like the Intranet.

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Web services - How? -I

The basic roles in a web services environment

} Provider - Creates and makes the web serviceavailable.

} Requester Uses the services provided by a webservice

} Registry The central data base where the providerpublishes the web service. The requestor looks up thisregistry to make out the available web services.

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SOA Service Oriented Architecture

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Web Services How? II

} The provider of a web service creates it and

publishes it in a central register (UDDI) in order

to enable the requestors to find the service.

} The web service is hosted generally on a web

server from where the users can access it.

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Web Services How? III

} The provider provides a description of the webservice functionality and other features usingWSDL (Web Service description Language)

} Once the provider and the requester or user of

the web service agree on the service descriptionand semantics are carried on to the providerand requester agents.

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Web Services How? IV} The provider and requester agents then exchange

messages on behalf of the provider and requester

entities.

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Web Services and Standards

} Universal Standards required since web

services involve communication between

systems of varied types irrespective of their

} Platform

} Controlling organization

} Implementation Language

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Standards used in web services

} XML Extensible Markup Language

} SOAP Simple Object Access Protocol

}WSDL Web Service Description Language

} UDDI Universal Description Discovery and

Integration

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Web Services Technology Stack

UDDIDiscovery

WSDLDescription

SOAPPackaging

HTTPNetwork

TCP/IPTransport

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XML ExtensibleMarkup Language} All data and documents in web services are

transferred as XML documents

} It is a subset of SGML (Standard Generalized

Markup Language)

} XML is an extensible markup language becauseunlike HTML the users of XML can define anduse their own new tags.

}

XML is the formal recommendation of the W3C(World Wide Web Consortium) for use in webservices.

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Advantages ofXML} XML is platform independent and thus is the

preferred choice for web services

} XML offers a standard, flexible and inherently

extensible data format

} Unlike HTML, XML is not concerned only with

the display of data but also the data itself

} XML is extremely portable and thus can be used

with very large applications as well as handheld devices like PDA and mobile phones.

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SOAP- Simple object Access Protocol

} SOAP is the W3C recommended protocol for web servicescommunication

} Is based on XML and transfers XML data over HTTPprotocol

} Both the request and response are in the form of SOAPmessages

} Messages are packaged inside SOAP Envelopes

} SOAP binds the client to the web service

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SOAP Communication

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SOAP Envelope

< SOAP-ENV:Header>

...

< SOAP-ENV:Body>

...

...

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UDDI- Universal Description,

Discovery and Integration

} UDDI is a central directory where services can be

registered and found

} Uses standards like HTTP, XML and DNS.

} Services can be searched for based on different

categories.

} Uses WSDL to describe the service interface

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WSDL- Web Services DescriptionLanguage

}WSDL is a document which is used to locate and

describe a web service

} Created in XML format

} It describes the location of the web servicealong with the operations exposed by it.

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WSDL -II} The major elements of a WSDL include:

An abstract definition of theoperations exposed by the service

Describes the parts of each messageand their types

Defines the data types used by the

web service

Defines the format of the messageand the protocols used.

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Bit Torrent

} Is a protocol for peer to peer file sharing.

}

Used mainly for distributing large amounts ofdata

} Seeders upload a file and make it available for

download by leechers or peers.

} The files are downloaded in pieces.

} Once a piece of file is downloaded, the leecher

can seed it for download by another peer.

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N

apster} Is an online music store which offers users a

variety of subscription and purchase options.

} It was launched in 1999 by Shawn Fanning

} It was originally a service which allowed peer topeer sharing of music (mp3) files.

} It was sued by many big recording companies

for copy rights infringement and had to shut

operations in 2001

} It is currently owned by Best Buy and offers

music to users on paid basis a cut of which goes

to the record companies

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Napster -II

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Freenet} Freenet is a censorship resistant software that

allows users to publish and read content

anonymously.

} Freenet is said to be totally free of any bodyscontrol including the creators.

} Users using Freenet donate storage space and

bandwidth to enable peer to peer content

sharing.} Countries like China have chosen to block

Freenet with their national Firewall.

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Gnutella -I} Gnutella is a large peer to peer file sharing network

} The network consists of nodes designated as peers

or ultra peers.

} A query is forwarded by peers to connected ultra

peers and forwarded by them to other connected

ultra peers.

} Once the query is resolved the concerned nodes

connect directly using UDP and initiate file transfer

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Gnutella -II

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Summary

} P2P technologies like web services and

Bittorent make the systems ultra scalable

} P2P technologies also increase the availability

of the systems and resources.

} P2P systems contribute in breaking the

information monopolies of large market players

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