Understanding Web Services

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?

• 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 that
• processes credit card transactions
• for a given account
• a market data service that
• provides stock market data
• associated with a specified
• stock 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

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Role of SOAP
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

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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

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SOAP Structure
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SOAP Example

• ltenvEnvelope xmlnsenv"http//www.w3.org/2001/06
  /soap-envelope" gt
• ltenvHeadergt
• lt/envHeadergt
• ltenvBodygt
• ltmGetLastTradePrice envencodingStyle
  "http//www.w3.org/2001/06/soap-encoding"
  xmlnsm"http//example.org/2001/06/quotes"gt
• ltsymbolgtDISlt/symbolgt
• lt/mGetLastTradePricegt
• lt/envBodygt
• lt/envEnvelopegt

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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

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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

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WSDL

• 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

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WSDL

• How does the client talk to the service?
• HTTP/SMTP/FTP
• Where is the location of the web service?
• The access point (URL)

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WSDL

•   lt?xml version"1.0" encoding"UTF-8" ?gt
• ltwsdldefinitions
• targetNamespace"http//137.189.94.1368080/axis/
  echo.jws" xmlns"http//schemas.xmlsoap.org/wsdl/"
  xmlnsapachesoap"http//xml.apache.org/xml-soap"
  xmlnsimpl"http//137.189.94.1368080/axis/echo.
  jws" xmlnsintf"http//137.189.94.1368080/axis/e
  cho.jws" xmlnssoapenc"http//schemas.xmlsoap.org
  /soap/encoding/" xmlnswsdl"http//schemas.xmlsoa
  p.org/wsdl/" xmlnswsdlsoap"http//schemas.xmlsoa
  p.org/wsdl/soap/" xmlnsxsd"http//www.w3.org/200
  1/XMLSchema"gt
• ltwsdlmessage name"echoStringResponse"gt 
• ltwsdlpart name"echoStringReturn"
  type"xsdstring" /gt  
• lt/wsdlmessagegt
• ltwsdlmessage name"echoStringRequest"gt 
• ltwsdlpart name"str" type"xsdstring" /gt  
• lt/wsdlmessagegt

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WSDL

• ltwsdlportType name"echo"gt
• ltwsdloperation name"echoString"
  parameterOrder"str"gt 
• ltwsdlinput message"intfechoStringReq
  uest"
• name"echoStringRequest" /gt  
• ltwsdloutput message"intfechoStringResponse
  " name"echoStringResponse" /gt  
• lt/wsdloperationgt 
• lt/wsdlportTypegt
• ltwsdlbinding name"echoSoapBinding"
  type"intfecho"gt 
• ltwsdlsoapbinding style"rpc"
  transport"http//schemas.xmlsoap.org/soap/http"
  
• /gt
• ltwsdloperation name"echoString"gt 
• ltwsdlsoapoperation soapAction"" /gt
• ltwsdlinput name"echoStringRequest"gt 
• ltwsdlsoapbody encodingStyle"http//schem
  as.xmlsoap.org/soap/encoding/"
• namespace"http//137.189.94.1368080/a
  xis/echo.jws" use"encoded" /gt  
• lt/wsdlinputgt

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WSDL

• ltwsdloutput name"echoStringResponse"gt 
• ltwsdlsoapbody
• encodingStylehttp//schemas.xmlsoap.org/
  soap/encoding/
• namespacehttp//137.189.94.1368080/ax
  is/echo.jws
• use"encoded" /gt  
• lt/wsdloutputgt 
• lt/wsdloperationgt 
• lt/wsdlbindinggt
• ltwsdlservice name"echoService"gt
• ltwsdlport binding"intfechoSoapBinding"
  name"echo"gt 
• ltwsdlsoapaddress location"http//137.1
  89.94.1368080/axis/echo.jws" /gt  
• lt/wsdlportgt 
• lt/wsdlservicegt 
• lt/wsdldefinitionsgt

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

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

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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

• QA