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Web Based Applications
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  1. Web Based Applications

  2. Basic Building Blocks • HTTP/HTTPS • XML • EXtensible Markup Language • Designed to carry data • User-defined tags <?xml version="1.0" encoding="ISO-8859-1"?> <note id="501"> <to>ABC</to> <from>XYZ</from> <heading>Reminder</heading> <body>Call 123</body> </note>

  3. XML Namespace <root> <h:table xmlns:h="http://www.w3.org/TR/html4/"> <h:tr> <h:td>Apples</h:td> <h:td>Bananas</h:td> </h:tr> </h:table> <f:table xmlns:f="http://www.w3schools.com/furniture"> <f:name>African Coffee Table</f:name> <f:width>80</f:width> <f:length>120</f:length> </f:table> </root>

  4. XML Schema <?xml version="1.0"?> <note xmlns=“http://www.w3schools.com” xmlns:xsi=“http://www.w3.org/2001/XMLSchema-instance” xsi:schemaLocation="http://www.w3schools.com note.xsd"> <to>Tove</to> <from>Jani</from> <heading>Reminder</heading> <body>Don't forget me this weekend!</body> </note>

  5. XML Schema <?xml version="1.0"?> <xs:schema xmlns:xs=“http://www.w3.org/2001/XMLSchema” targetNamespace=“http://www.w3schools.com” xmlns=“http://www.w3schools.com” elementFormDefault="qualified"> <xs:element name="note"> <xs:complexType> <xs:sequence> <xs:element name="to" type="xs:string"/> ….. </xs:sequence> </xs:complexType> </xs:element> </xs:schema>

  6. Web Services • Defined as “a software system designed to support interoperable Machine to Machine interaction over a network “ • Components are • SOAP • WSDL • UDDI

  7. SOAP • Simple Object Access Protocol • A protocol for exchanging XML-based messages over computer networks • Works on top of HTTP/HTTPS • Advantage • Work over http proxies • Disadvantage • Slower

  8. SOAP Message A SOAP message contains: • Envelope element • Header element (optional) • Body element • Fault element (optional)

  9. SOAP Message Example <?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:header> ... ... </soap:header> <soap:Body> ... ... <soap:fault> ... ... </soap:fault> </soap:Body> </soap:Envelope>

  10. Request <?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> <m:GetPrice xmlns:m="http://www.w3schools.com/prices"> <m:Item>Apples</m:Item> </m:GetPrice> </soap:Body> </soap:Envelope>

  11. Response <?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> <m:GetPriceResponse xmlns:m="http://www.w3schools.com/prices"> <m:Price>1.90</m:Price> </m:GetPriceResponse> </soap:Body> </soap:Envelope>

  12. WSDL • Web Service Description Language • Provides a model for describing Web Services • Defines services as collections of network endpoints, or ports • Client program parses the WSDL description of the services offered by the server

  13. Document Structure <definitions> <types>…………definition of types........……</types> <message>.……definition of a message......</message> <portType>.……definition of a port...............</portType> <binding>………definition of a binding……..</binding> </definitions>

  14. WSDL Example <message name="getTermRequest"> <part name="term" type="xs:string"/> </message> <message name="getTermResponse"> <part name="value" type="xs:string"/> </message> <portType name="glossaryTerms"> <operation name="getTerm"> <input message="getTermRequest"/> <output message="getTermResponse"/> </operation> </portType>

  15. Example contd. <binding type="glossaryTerms" name="b1"> <soap:binding style="document“ transport="http://schemas.xmlsoap.org/soap/http" /> <operation> <soap:operation soapAction="http://example.com/getTerm"/> <input> ……<soap:body use="literal"/> …….</input> <output>…..<soap:body use="literal"/>………</output> </operation> </binding>

  16. UDDI • Universal Description, Discovery and Integration • A platform-independent, XML-based registry for businesses worldwide to list themselves on the Internet • Open industry initiative, sponsored by OASIS • Consists of the following components • White Pages • Information about WS providers • Yellow Pages • Available Web services • Green Pages • Technical interfaces for to access and manage WS

  17. Models of Web Services • RPC • Message Oriented • Service Oriented • Resource Oriented • Policy Based

  18. BPEL4WS • Used for defining a new Web service by composing a set of existing services • Primitive activities • Invoke, Receive, Reply, Wait, Assign, Throw, Terminate. • Structure activities • Sequence, Switch, While, Pick, Flow • Partners

  19. Example

  20. Semantic Web • Goal is to express the web content in such a format, which can be read and used by software • Uses the following standards • XML • XML Schema • RDF • RDF Schema • OWL • SPARQL

  21. Semantic Web Contd. • RDF • a general method of modeling information, through a variety of syntax formats • Expresses knowledge about resources in the form of subject-predicate-object expressions • Resource is named by Uniform Resource Identifier (URI).

  22. Semantic Web contd. • XML Schema • expresses a schema: a set of rules to which an XML document must conform in order to be considered 'valid' according to that schema • RDF Schema • Knowledge representation language • Describes predominantly in terms class, subclass, domain and range

  23. Semantic Web contd. • OWL • Web Ontology Language • adds more vocabulary for describing properties and classes than RDF Schema • SPARQL • protocol and query language for semantic web data sources