Web Based Applications
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>
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>
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>
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>
Web Services Defined as “a software system designed to support interoperable Machine to Machine interaction over a network “ Components are SOAP WSDL UDDI
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
SOAP Message A SOAP message contains: Envelope element Header element (optional) Body element Fault element (optional)
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>
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>
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>
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
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>
WSDL Example <message name="getTermRequest"> <part name="term" type="xs:string"/> </message> <message name="getTermResponse"> <part name="value" type="xs:string"/> <portType name="glossaryTerms"> <operation name="getTerm"> <input message="getTermRequest"/> <output message="getTermResponse"/> </operation> </portType>
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>
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
Models of Web Services RPC Message Oriented Service Oriented Resource Oriented Policy Based
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
Example
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
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).
Semantic Web contd. XML Schema RDF 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
Semantic Web contd. OWL SPARQL Web Ontology Language adds more vocabulary for describing properties and classes than RDF Schema SPARQL protocol and query language for semantic web data sources