Applying xml

Applying xml

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  Applying XML
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  XML and WebServices • XML web services are basic building blocks in the era of distributed computing • Demand for XML web services: – Open standards focuses on communication and collaboration between people and applications – Web services have become an platform for the application integration – Applications have been developed with multiple XML web services from various sources work together regardless of where these services resides and how these services are implemented.
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  Contd.. • XML Webservices – Work with standard web protocols like XML, HTTP and TCP/IP – exposes many functionality to the user through the web protocol (SOAP). – provides a means to describe their interfaces, which allows the user to build a client application to interact with them and described in document called WSDL – must be registered so that users can find them and done through UDDI. – allows programs written in different language and in different architecture to communicate with one another in a standard way. • XML web service is defined as the software service exposed on the web through the SOAP protocol and described with a WSDL file and registered in the UDDI
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  Contd.. • Examples: – StockQuotes – Weather Forecasts – Sports Scores – Calendar Service • These services can be accessed freely whereas some might require a subscription to the service • Makes the programmatic access easier and much more reliable. • Exposing existing applications as a web service allows users rapidly to develop new applications based on these web services. – For e.g., a web service for purchasing application is developed where in which this application obtains the price info from a variety of vendors, allowing the user to select a specific vendor, submitting the order and then track the shipment details until it is received – This might in turn use another web service to check the customers credit, manage the customer’s account.
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  SOAP (Simple ObjectAccess Protocol) • A communication protocol for Web services. • A specification which defines the XML format for messages. • SOAP message contains the callable function, parameters required to pass the function which is sent from the client and the server returns the message with the results • SOAP tool kits will translate the function calls from some language to a SOAP message. – For example Apache tool kit translates the java function calls in to SOAP messages • SOAP is been implemented on many different hardware and software platforms.
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  WSDL (Web ServicesDescription Language) • WSDL file describes the message formats and how these messages are exchanged. • It is based on the XML schema standard which makes the web services interfaces accessible from variety of platforms and programming languages. • It also defines where the services are available, what communication protocol is used.
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  UDDI • UDDI standsfor Universal Discovery Description and Integration. • It is like the yellow pages for the Web services. • Yellow pages are used to search for the company that offers services we need, read the services offered and contact someone for more info. • UDDI directory includes several ways to search for the services that we need to build our applications. • Web services can be offered without registering it in the UDDI, but UDDI is required for the customers to find you. • For e.g., we can search for providers of a service in a specified geographic location or for business of a specified type. • The UDDI directory will then supply info, contacts, links, and technical data to allow us to evaluate which services meet our requirements.
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  Web service Architecture
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  HTML with XML •Data in XML can be described by itself. • The question of how data is loaded to the application and displayed to the user is left to the application program. • Normally web application allows user to display the stored data through web browser. • XML data can also be transformed to HTML which can then be viewed in the web page. • The transformation of XML to HTML can be done in two different ways – DOM/SAX parser which helps in loading XML data into html page and formatting it in to a HTML document. – XSLT, which helps in describing the transformation rules from XML to HTML and display it in the web page.
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  XSLT • XSLT standsfor Extensible Style sheet Language Transformations • XSLT is an XML-related Language which helps in manipulating and transforming XML documents.
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  Contd..
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  XSLT Document • Theroot element of the XSL document is <xsl:stylesheet> • To include the XSLT is XML document: <?xml-stylesheet type="text/xsl" href=“filename.xsl"?>