1

Understanding Web Services

Presented By: Woodas Lai

2

Understanding Web Services By Jaideep Roy and Anupama Ramanujan

What is Web Services? Architecture Core technologies

XML SOAP WSDL UDDI

3

What is Web Services?What is Web Services?

A Web Services is a unit of application logic providing data and services to

other applications

They are published to the Web in such a way

that other applications can find and use them

4

Examples of Web Services

a credit card service thatprocesses credit card transactionsfor a given account

a market data service thatprovides stock market dataassociated with a specifiedstock symbol

5

Architecture

6

Core Technologies Technologies for Web Services

XML UDDI ( XML Based ) SOAP ( XML Based ) WSDL ( XML Based )

7

SOAP

Simple Object Access Protocol (SOAP)http://www.w3.org/TR/SOAP/

A lightweight XML communication message protocol

8

Role of SOAP

.NETapplication

J avaApplication

SOAP ClientSOAPServer

.NET function callrequest

Binary

Perform Serialization orMarshalling

Perform De-Serializationor Un-Marshalling

XML (Text Based)

Binary J ava function callrequest

SOAP Message

9

SOAP Overview

Describe the messaging format for machine-to-machine communication

Enable procedure calls on remote objects Define elements to specify remote function

names, parameters and return types

10

SOAP Overview

Support different Internet protocols, such as HTTP, SMTP, FTP (Protocol neutral)

SOAP = XML + RPC + HTTP (Typical use) A SOAP document is an XML document

designed to invoke methods on remote computers over HTTP

11

SOAP Structure

Header (Optional)

Body (Mandatory)

SOAP Message

Envelope

12

SOAP Example<env:Envelope xmlns:env="http://www.w3.org/2001/06/soap-envelope" >

<env:Header>……

</env:Header><env:Body>

<m:GetLastTradePrice env:encodingStyle= "http://www.w3.org/2001/06/soap-encoding

" xmlns:m="http://example.org/2001/06/quotes"><symbol>DIS</symbol>

</m:GetLastTradePrice></env:Body>

</env:Envelope>

13

WSDL Web Services Description Language (WSDL)

http://www.w3.org/TR/wsdl

Description of Web Services via XML-based standard format

Define the set of functions supported by the server and the formats a client should be used to request the service, like IDL in CORBA

14

WSDL WSDL is used to describe the web

services. So, how to describe? WSDL has its own XML vocabulary

defined so as to describe the web service

15

WSDL has a well-defined XML vocabulary to answer

the following questions regarding the web service

involved: What does the service do?

Both in machine and human-readable forms What language does the service speak?

The format/data structure of the message exchanged

WSDL

16

How does the client talk to the service? HTTP/SMTP/FTP

Where is the location of the web service? The access point (URL)

WSDL

17

WSDL  <?xml version="1.0" encoding="UTF-8" ?> <wsdl:definitions

targetNamespace="http://137.189.94.136:8080/axis/echo.jws" xmlns="http://schemas.xmlsoap.org/wsdl/" xmlns:apachesoap="http://xml.apache.org/xml-soap" xmlns:impl="http://137.189.94.136:8080/axis/echo.jws" xmlns:intf="http://137.189.94.136:8080/axis/echo.jws" xmlns:soapenc="http://schemas.xmlsoap.org/soap/encoding/" xmlns:wsdl="http://schemas.xmlsoap.org/wsdl/" xmlns:wsdlsoap="http://schemas.xmlsoap.org/wsdl/soap/" xmlns:xsd="http://www.w3.org/2001/XMLSchema"><wsdl:message name="echoStringResponse">  <wsdl:part name="echoStringReturn" type="xsd:string" />   </wsdl:message><wsdl:message name="echoStringRequest">  <wsdl:part name="str" type="xsd:string" />   </wsdl:message>

18

WSDL <wsdl:portType name="echo"> <wsdl:operation name="echoString" parameterOrder="str">  <wsdl:input message="intf:echoStringRequest"

name="echoStringRequest" />   <wsdl:output message="intf:echoStringResponse"

name="echoStringResponse" />   </wsdl:operation>  </wsdl:portType> <wsdl:binding name="echoSoapBinding" type="intf:echo">  <wsdlsoap:binding style="rpc" transport="http://schemas.xmlsoap.org/soap/http" /> <wsdl:operation name="echoString">  <wsdlsoap:operation soapAction="" /> <wsdl:input name="echoStringRequest">  <wsdlsoap:body encodingStyle="http://schemas.xmlsoap.org/soap/encoding/" namespace="http://137.189.94.136:8080/axis/echo.jws" use="encoded" />   </wsdl:input>

19

WSDL <wsdl:output name="echoStringResponse"> 

<wsdlsoap:body encodingStyle=http://schemas.xmlsoap.org/soap/encoding/

namespace=http://137.189.94.136:8080/axis/echo.jws

use="encoded" />   </wsdl:output>  </wsdl:operation>  </wsdl:binding> <wsdl:service name="echoService"> <wsdl:port binding="intf:echoSoapBinding" name="echo">  <wsdlsoap:address location="http://137.189.94.136:8080/axis/echo.jws" />   </wsdl:port> 

</wsdl:service>  </wsdl:definitions>

20

UDDI Universal Description, Discovery, and Integration Specifications for service description and discovery Open-Standard

Raised By Ariba, IBM and Microsoft http://www.uddi.org (by Oasis)

XML-based message

21

Service Architecture

UDDI defines a way to publish and discover information about Web services

22

UDDI

• Information about the business (company name, company address ……)

• Categorization of the business and its services

• Technical information about services provided by a business (like the URL to invoke the Web Services)

White Page

Yellow Page

Green Page

23

Core Structures of UDDI

• Business Entity• White Pages information

• Business Services• Yellow Pages information

• Binding Templates• Green Pages information • Contains references to tModels

• tModels• Service Type Definitions• Interface specifications for a service (WSDL)

Business Entity

BusinessService

tModel

tModel

BindingTemplate

BindingTemplate

24

Research Challenge How to secure the Web Services

Invocation? How to ensure the reliability of the

Web Services? How to deal with the Quality of

Services?

25

Q&A