Web Services Overview
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Transcript of Web Services Overview
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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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Next Chapter
• Establishing a foundation for web services