Web Based Applications

sounderslipInternet and Web Development

Oct 22, 2013 (4 years and 6 months ago)

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Web Based Applications

Basic Building Blocks

•
HTTP/HTTPS

•
XML

–
E
X
tensible
M
arkup
L
anguage

–
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"/>

</message>

<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

–
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

–
Web Ontology Language

–
adds more vocabulary for describing properties
and classes than RDF Schema

•
SPARQL

–
protocol and query language for semantic web
data sources