Web Services Overview Ashraf Memon. 2 Overview Service Oriented Architecture Web service overview Benefits of Web services Core technologies: XML, SOAP,

Web Services OverviewWeb Services Overview

Ashraf MemonAshraf Memon

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Overview

• Service Oriented Architecture

• Web service overview

• Benefits of Web services

• Core technologies: XML, SOAP, WSDL

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Service Oriented Architectures• essentially a collection of services.

• services communicate with each other.

Service Provider

ServiceConsumerResponse

Request

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• communication can involve either simple data passing.

Service Oriented Architectures

Service Provider

ServiceConsumer

Response

Request

Service Provider

Procedure/Workflow

Request/Response

Service Provider

Service Provider

Request/Response

Request/Response

Service Consumer

Data

Data

Data

Data

• could also involve two or more services coordinating some activity.

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• Service Oriented Architectures are not new• Previous implementation

– DCOM - Distributed Component Object Model (Microsoft)

– ORB Object Request Brokers based on CORBA Specifications (Java)

• Very Complex – Non standard interchange format– Binary information interchange– Very few tools

• New Implementations– Web Services

Service Oriented Architectures

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What are Web Services?

• A Web Service is programmable application logic accessible using standard Internet protocols.

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Web services

Piece of Code

Database

Files

ToolMS COM

C

Java

Perl

Fortran

Other tools

• Web service is any piece of code that can be made available over the Internet, so that other applications can invoke it and utilize its functionality.

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What are Web Services? ….

Piece of Code

DeploymentScript

Soap Server

Service Provider

Code

ServiceDescription

Soap Client

API

Service Client

SOAPover

HTTP

Service Description

Soap L

istener

Header

Body

ServiceResponse

Response

Soap Body

Request

Header

Request Params

Body

WSDL

SOAP

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Benefits of Web Services

• Facilitates reuse of existing assets• Lower cost of maintenance• Reduced impact of change• Example

– GRIDgrid• AsciiToMap, XMLToMap, ShapeToMap• Benefits include availability of useful functionality on the web

– Arcweb Services• Pool of web services that provide mechanism to access data and GIS

functions on demand.• Benefits include, access to terabytes of spatial data, complex GIS

functionality, etc.

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XML

• XML is a programming/formatting language and is basically another version of HTML

• It provides a mechanism to describe structure and organization of Data

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XML Example<?xml version=“1.0”?>

<Names><Name>Adam Bosworth</Name>

<Title>General Manager </Title> <Phone>222-444-666</Phone> <Company>XYZ Corp.</Company>

<PIN>2468</PIN> </Names>

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SOAP

• SOAP stands for Simple Object Access Protocol.

• SOAP is a simple XML based protocol to let applications exchange information over HTTP.

• SOAP is a protocol for accessing a Web Service.

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SOAP ExamplePOST /InStock HTTP/1.1 Host: www.stock.org Content-Type: application/soap+xml; charset=utf-8 Content-Length: nnn

<?xml version="1.0"?> <soap:Envelope

xmlns:soap="http://www.w3.org/2001/12/soap-envelope" soap:encodingStyle="http://www.w3.org/2001/12/soap-encoding"> <soap:Body

xmlns:m="http://www.stock.org/stock">    <m:GetStockPrice>

<m:StockName>IBM</m:StockName>     </m:GetStockPrice>

</soap:Body></soap:Envelope>

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WSDL

• WSDL stands for Web Services Description Language

• WSDL (Web Services Description Language) is an XML-based language for describing Web services and how to access them.

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WSDL Example

• URL

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Next Chapter

• Establishing a foundation for web services