Web Services

1
Web Services

• Representation and Management of Data on the Web

2
"Web services are loosely coupled software
components delivered over Internet standard
technologies."
3
Example Scenario Get Online Information
Stock Broker Application
Stock Exchange
4
Example Scenario Online Trade
Book Store
The Hobbit (5) Price 25.95 Copies in Stock 1
The Hobbit (5) Price 25.95 Copies in Stock 0
5
Example ScenarioGrid Computation
Grid Computation
Using seamlessly the combined resources of many
computers that are connected to the Internet
6
What is a Web Service?

• Self-contained, modular Web application that can
  be published, located and invoked across the Web
• A Web service can perform functions of varying
  complexities
• Once deployed, other applications (and other Web
  services) can discover and invoke the deployed
  service

7
Why is it Difficult to Use Ordinary Web Sites as
Services?

• Consider an application that should return the
  price of the book The Hobbit
• How can your application find suitable online
  stores?
• How can your application find the price of the
  book in a Web page?
• How can your application fill forms, if needed?

8
How can we find this URL?
What is the price here?
9
Calling Remote FunctionsCould Help

• It would help if we could call functions, such
  as
• Amazon.getPrice(The Hobbit")
• Amazon.buyBook(The Hobbit", myId)

getPrice()
The Internet
10
Difficulties in UsingRemote Functions

• How can the calling application know in what
  language the functions are written?
• How can the application know what functions are
  available and what are their signatures?
• How can an application call a function that
  resides behind a firewall?

11
The Solution

• Use an agreed interface and a syntax that all
  applications are familiar with (e.g., XML)
• For example, SOAP
• Use HTTP to transfer data through port 80
• Use a standard for publishing methods, their
  signatures and their usage
• For example, WSDL
• Use standard directory structures for publishing
  available services
• For example, UDDI

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(No Transcript)
13
Web Services that areAlready Available

• Google search (http//www.google.com/apis)
• Weather reports
• Stock prices
• Currency exchanges
• Sending SMS messages, faxes
• Prices of books in Barnes and Nobles
• Dictionaries
• etc.

14
Implementing Web Services

• Programmers are given tools that spare the need
  to directly write SOAP or WSDL documents
• In Java
• JAX-RPC part of SUN tools for publishing and
  deploying Web Services
• AXIS Apaches tool for handling Web services in
  Java

15
SOAPSimple Object-Access Protocol
16
What is SOAP?

• SOAP is a protocol for accessing Web Services
• SOAP is XML based
• Thus, SOAP provides interoperability
• In SOAP, applications exchange information over
  HTTP
• Thus, SOAP is not restricted by firewalls
• SOAP allows to exchange structured and typed
  information on the Web
• XSchema types are used to add types to XML
• SOAP specification http//www.w3.org/2000/xp/Grou
  p/

17
POST /soap HTTP/1.0 SOAPAction
"" Content-Length 520 lt?xml version"1.0"
encoding"UTF-8"?gt ltsoapenvEnvelope
xmlnssoapenv"http//schemas.xmlsoap.org/soap/e
nvelope/" xmlnsxsd"http//www.w3.o
rg/2001/XMLSchema"
xmlnsxsi"http//www.w3.org/2001/XMLSchema-instan
ce"gt ltsoapenvBodygt ltns1getRate
soapenvencodingStyle"http//schemas.xmlsoap.o
rg/soap/encoding/" xmlnsns1"urnxmethod
s-CurrencyExchange"gt ltcountry1
xsitype"xsdstring"gtEurolt/country1gt
ltcountry2 xsitype"xsdstring"gtIsraellt/country2gt
lt/ns1getRategt lt/soapenvBodygt lt/soapenvEnvel
opegt
A request to http//services.xmethods.net80/soap
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HTTP/1.0 200 OK Date Sat, 07 May 2005 232621
GMT Content-Length 492 Content-Type
text/xml lt?xml version'1.0' encoding'UTF-8'?gt lt
soapEnvelope xmlnssoap'http//schemas.xml
soap.org/soap/envelope/'
xmlnsxsi'http//www.w3.org/2001/XMLSchema-instan
ce' xmlnsxsd'http//www.w3.org/2001/XMLS
chema' xmlnssoapenc'http//schemas.xmlsoap
.org/soap/encoding/' soapencodingStyle'htt
p//schemas.xmlsoap.org/soap/encoding/'gt
ltsoapBodygt ltngetRateResponse
xmlnsn'urnxmethods-CurrencyExchange'gt
ltResult xsitype'xsdfloat'gt5.5825lt/Res
ultgt lt/ngetRateResponsegt
lt/soapBodygt lt/soapEnvelopegt
The Response
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A SOAP Message

• A SOAP message is an ordinary XML document
  containing the following elements
• Envelope identifies the XML document as a SOAP
  message required
• Header contains header information optional
• Body contains call or response information
  required
• Fault provides information about errors that
  occurred while processing the message optional

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SOAP Simplification (1)

• Consider the Java interface
• Suppose that a client wants to call the server's
  sayHelloTo method
• Could send an XML message

public interface Hello public String
sayHelloTo(String name)
lt?xml version"1.0"?gtltHellogt    ltsayHelloTogt   
     ltnamegtLisalt/namegt    lt/sayHelloTogtlt/Hellogt
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SOAP Simplification (2)

• The Server could respond with

lt?xml version"1.0"?gtltHellogt    ltsayHelloToRespo
nsegt       ltmessagegtHello Lisa, How are
you?lt/messagegt    lt/sayHelloToResponsegtlt/Hellogt
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SOAP Intuition
23
Skeleton SOAP Message
lt?xml version"1.0"?gt ltsoapEnvelope
xmlnssoap"http//schemas.xmlsoap.org/soap/envelo
pe/" soapencodingStyle"http//schemas.xmlsoap.or
g/soap/encoding/"gt ltsoapHeadergt ... ...
lt/soapHeadergt ltsoapBodygt ... ...
ltsoapFaultgt ... ... lt/soapFaultgt
lt/soapBodygt lt/soapEnvelopegt
Envelope
Header
Body
Fault
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encodingStyle Attribute

• The SOAP encodingStyle attribute indicates the
  encoding rules used to serialize parts of a SOAP
  message
• Needed when sending data structures
• This attribute may appear on any SOAP element,
  and it will apply to that element's content and
  all child elements
• A SOAP message has no default encoding
• Unencoded data may be used in SOAP messages
• The SOAP default XMLSchema for SOAP encoding and
  data types is
• http//www.w3.org/2002/12/soap-encoding
• Other encoding rules may be used

25
Actual Soap Request

• ltSOAP-ENVEnvelope
• xmlnsSOAP-ENV"http//schemas.xmlsoap.org/soap
  /envelope/"
• xmlnsxsi"http//www.w3.org/1999/XMLSchema-ins
  tance"
•    xmlnsxsd"http//www.w3.org/1999/XMLSchema"gt 
     ltSOAP-ENVHeadergt lt/SOAP-ENVHeadergt    ltSOAP-
  ENVBodygt         ltns1sayHelloTo
   xmlnsns1"Hello"
• SOAP-ENVencodingStyle"
• http//schemas.xmlsoap.org/s
  oap/encoding/"gt           ltname
  xsitype"xsdstring"gtLisalt/namegt        
  lt/ns1sayHelloTogt    lt/SOAP-ENVBodygt
• lt/SOAP-ENVEnvelopegt

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Actual Soap Request

• ltSOAP-ENVEnvelope
• xmlnsSOAP-ENV"http//schemas.xmlsoap.org/soap
  /envelope/"
• xmlnsxsi"http//www.w3.org/1999/XMLSchema-ins
  tance"
•    xmlnsxsd"http//www.w3.org/1999/XMLSchema"gt 
     ltSOAP-ENVHeadergt lt/SOAP-ENVHeadergt    ltSOAP-
  ENVBodygt         ltns1sayHelloTo
   xmlnsns1"Hello"
• SOAP-ENVencodingStyle"
• http//schemas.xmlsoap.org/s
  oap/encoding/"gt           ltname
  xsitype"xsdstring"gtLisalt/namegt        
  lt/ns1sayHelloTogt    lt/SOAP-ENVBodygt
• lt/SOAP-ENVEnvelopegt

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Actual Soap Request

• ltSOAP-ENVEnvelope
• xmlnsSOAP-ENV"http//schemas.xmlsoap.org/soap
  /envelope/"
• xmlnsxsi"http//www.w3.org/1999/XMLSchema-ins
  tance"
•    xmlnsxsd"http//www.w3.org/1999/XMLSchema"gt 
     ltSOAP-ENVHeadergt lt/SOAP-ENVHeadergt    ltSOAP-
  ENVBodygt         ltns1sayHelloTo
   xmlnsns1"Hello"
• SOAP-ENVencodingStyle"
• http//schemas.xmlsoap.org/s
  oap/encoding/"gt           ltname
  xsitype"xsdstring"gtLisalt/namegt        
  lt/ns1sayHelloTogt    lt/SOAP-ENVBodygt
• lt/SOAP-ENVEnvelopegt

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Actual Soap Request

• ltSOAP-ENVEnvelope
• xmlnsSOAP-ENV"http//schemas.xmlsoap.org/soap
  /envelope/"
• xmlnsxsi"http//www.w3.org/1999/XMLSchema-ins
  tance"
•    xmlnsxsd"http//www.w3.org/1999/XMLSchema"gt 
     ltSOAP-ENVHeadergt lt/SOAP-ENVHeadergt    ltSOAP-
  ENVBodygt         ltns1sayHelloTo
   xmlnsns1"Hello"
• SOAP-ENVencodingStyle"
• http//schemas.xmlsoap.org/s
  oap/encoding/"gt           ltname
  xsitype"xsdstring"gtLisalt/namegt        
  lt/ns1sayHelloTogt    lt/SOAP-ENVBodygt
• lt/SOAP-ENVEnvelopegt

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Actual Soap Response

• ltSOAP-ENVEnvelope
• xmlnsSOAP-ENV"http//schemas.xmlsoap.org/soap
  /envelope/"
•    xmlnsxsi"http//www.w3.org/1999/XMLSchema-ins
  tance"
• xmlnsxsd"http//www.w3.org/1999/XMLSchema"gt 
     ltSOAP-ENVBodygt          ltns1sayHelloToRespon
  se xmlnsns1"Hello"                SOAP-ENVenco
  dingStyle"
• http//schemas.xmlsoap.org
  /soap/encoding/"gt                 ltreturn
  xsitype"xsdstring"gt
• Hello Lisa, How are you doing?
• lt/returngt          lt/ns1sayHelloToResponsegt 
     lt/SOAP-ENVBodygt
• lt/SOAP-ENVEnvelopegt

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Actual Soap Response

• ltSOAP-ENVEnvelope
• xmlnsSOAP-ENV"http//schemas.xmlsoap.org/soap
  /envelope/"
•    xmlnsxsi"http//www.w3.org/1999/XMLSchema-ins
  tance"
• xmlnsxsd"http//www.w3.org/1999/XMLSchema"gt 
     ltSOAP-ENVBodygt          ltns1sayHelloToRespon
  se xmlnsns1"Hello"                SOAP-ENVenco
  dingStyle"
• http//schemas.xmlsoap.org
  /soap/encoding/"gt                 ltreturn
  xsitype"xsdstring"gt
• Hello Lisa, How are you doing?
• lt/returngt          lt/ns1sayHelloToResponsegt 
     lt/SOAP-ENVBodygt
• lt/SOAP-ENVEnvelopegt

Body
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Actual Soap Response

• ltSOAP-ENVEnvelope
• xmlnsSOAP-ENV"http//schemas.xmlsoap.org/soap
  /envelope/"
•    xmlnsxsi"http//www.w3.org/1999/XMLSchema-ins
  tance"
• xmlnsxsd"http//www.w3.org/1999/XMLSchema"gt 
     ltSOAP-ENVBodygt          ltns1sayHelloToRespon
  se xmlnsns1"Hello"                SOAP-ENVenco
  dingStyle"
• http//schemas.xmlsoap.org
  /soap/encoding/"gt                 ltreturn
  xsitype"xsdstring"gt
• Hello Lisa, How are you doing?
• lt/returngt          lt/ns1sayHelloToResponsegt 
     lt/SOAP-ENVBodygt
• lt/SOAP-ENVEnvelopegt

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SOAP Header Element

• The SOAP Header element is optional
• It contains application specific information
  (like authentication, payment, etc) about the
  SOAP message
• If the Header element is present, it must be the
  first child element of the Envelope element
• Attributes that the namespace defines
• Actor used to address the Header element to a
  particular server (e.g., proxy) on the message
  path through the Internet
• mustUnderstand used to indicate whether a
  header entry is mandatory or optional for the
  recipient to process
• encodingStyle as explained before

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SOAP Header Element

• Example
• ltSOAP-ENVHeadergt     lttTransaction
  xmlnst"some-URI"
• SOAP-ENVmustUnderstand"1"gt5lt/tTransa
  ctiongt
• lt/SOAP-ENVHeadergt
• 5 is the transaction ID of which this method is a
  part
• In the above example, the SOAP-envelope attribute
  mustUnderstand is set to 1, which means that the
  server must either understand and honor the
  transaction request or must fail to process the
  message

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SOAP Response on Error

• There can be many errors in processing a SOAP
  request
• Error in Running Methods For example, suppose
  that the "Hello Server" does not allow anyone to
  say hello on Tuesday
• Error in Processing SOAP Headers For example, a
  problem running the method as part of a
  transaction

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The Fault Element May Include the Following
Sub-Elements

• ltfaultcodegt A code for identifying the fault
• ltfaultstringgt A human readable explanation of
  the fault
• ltfaultactorgt Information about who caused the
  fault
• ltdetailgt Holds application-specific error
  information related to the Body element of the
  SOAP request

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SOAP Fault Codes

• VersionMismatch Found an invalid namespace for
  the SOAP Envelope element
• MustUnderstand An immediate child element of the
  Header element, with the mustUnderstand attribute
  set to 1, was not understood
• Client The message was incorrectly formed or
  contained incorrect information
• Server There was a problem with the server so
  the message could not proceed

37
SOAP Error Response for Method Error

• ltSOAP-ENVEnvelope xmlnsSOAP-ENV"http//schemas
  .xmlsoap.org/soap/envelope/"gt  
  ltSOAP-ENVBodygt       ltSOAP-ENVFaultgt          
  ltfaultcodegtSOAP-ENVServerlt/faultcodegt          
  ltfaultstringgtServer Errorlt/faultstringgt         
    ltdetailgt               ltemyfaultdetails
  xmlnse"Hello"gt                
  ltmessagegt                   Sorry, I cannot say
  hello on Tuesday.                
  lt/messagegt                 lterrorcodegt1001lt/error
  codegt               lt/emyfaultdetailsgt         
    lt/detailgt       lt/SOAP-ENVFaultgt  
  lt/SOAP-ENVBodygtlt/SOAP-ENVEnvelopegt

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SOAP Error Response for Header Error

• ltSOAP-ENVEnvelope xmlnsSOAP-ENV"http//schemas
  .xmlsoap.org/soap/envelope/"gt  
  ltSOAP-ENVBodygt       ltSOAP-ENVFaultgt          
  ltfaultcodegtSOAP-ENVMustUnderstandlt/faultcodegt  
           ltfaultstringgtSOAP Must Understand
  Errorlt/faultstringgt      
  lt/SOAP-ENVFaultgt   lt/SOAP-ENVBodygtlt/SOAP-ENVE
  nvelopegt

No detail element may appear when there is an
error in processing the Headers of a SOAP request
39
Sending a Request

• The SOAP request does not contain the address to
  which it should be sent
• Q Where do we put the URL of the Web Service?
• A It depends on the Protocol used to send the
  request (usually HTTP, but could also be another
  protocol, e.g., SMTP)

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SOAP Request via HTTP

• POST http//www.Hello.com/HelloApplication
  HTTP/1.0
• Content-Type text/xml charsetUTF-8
• Content-Length 587
• SOAPAction urnhelloApp
• ltSOAP-ENVEnvelope

Note There are 2 addresses (1) URL of a SOAP
Server (2) URI of an application to run (this
needn't correspond to an
actual Internet address)
41
SOAPAction Header

• Used to indicate the intent of the SOAP HTTP
  request
• The presence and content of the SOAPAction header
  field can be used by servers, such as firewalls,
  to appropriately filter SOAP request messages in
  HTTP
• The header-field value of an empty string ("")
  means that the intent of the SOAP message is
  provided by the URL of the HTTP Request

42
SOAP Response via HTTP

• HTTP/1.0 200 OK
• Content-Type text/xml charsetUTF-8
• Content-Length 615
• ltSOAP-ENVEnvelope

43
Example Currency Rate

• There are many available Web services that you
  can use
• See http//www.xmethods.com/ for a list
• Look, in particular, at those marked "RPC"
  (Remote Procedure Call)
• To get Currency exchange, for example, you can do
  "telnet wwwproxy.cs.huji.ac.il 8080" and then
  send the following request

44

• POST http//services.xmethods.net80/soap
  HTTP/1.0
• Content-Type text/xml
• Content-Length 485
• SOAPAction ""
• ltSOAP-ENVEnvelope xmlnsSOAP-ENV"http//schemas.
  xmlsoap.org/soap/envelope/" xmlnsxsi"http//www.
  w3.org/1999/XMLSchema-instance"
  xmlnsxsd"http//www.w3.org/1999/XMLSchema"gt
• ltSOAP-ENVBodygt
• ltns1getRate xmlnsns1"urnxmethods-CurrencyExcha
  nge" SOAP-ENVencodingStyle"http//schemas.xmlsoa
  p.org/soap/encoding/"gt
• ltcountry1 xsitype"xsdstring"gtUnited
  Stateslt/country1gt
• ltcountry2 xsitype"xsdstring"gtIsraellt/country2gt
  
• lt/ns1getRategt
• lt/SOAP-ENVBodygtlt/SOAP-ENVEnvelopegt

45
And Here is the Response

• HTTP/1.0 200 OK
• Content-Type text/xml
• lt?xml version'1.0' encoding'UTF-8'?gt
• ltsoapEnvelope xmlnssoap'http//schemas.xmlsoap.
  org/soap/envelope/' xmlnsxsi'http//www.w3.org/1
  999/XMLSchema-instance' xmlnsxsd'http//www.w3.o
  rg/1999/XMLSchema' xmlnssoapenc'http//schemas.x
  mlsoap.org/soap/encoding/' soapencodingStyle'htt
  p//schemas.xmlsoap.org/soap/encoding/'gt
• ltsoapBodygtltngetRateResponse
• xmlnsn'urnxmethods-CurrencyExchange'gt
• ltResult xsitype'xsdfloat'gt4.521lt/Resultgt
• lt/ngetRateResponsegt
• lt/soapBodygtlt/soapEnvelopegt

46
Example - Calling Google Spelling

• lt?xml version"1.0" encoding"UTF-8" ?gt
• ltSOAP-ENVEnvelope xmlnsSOAP
• ENVhttp//schemas.xmlsoap.org/soap/envelope/
• xmlnsxsihttp//www.w3.org/1999/XMLSchema-inst
  ance
• xmlnsxsdhttp//www.w3.org/1999/XMLSchemagt
• ltSOAP-ENVBodygt
• ltns1doSpellingSuggestion xmlnsns1urnGoogl
  eSearch SOAP- ENVencodingStyle"http//schemas.
  xmlsoap.org/soap/encoding/"gt 
• ltkey xsitype"xsdstring"gt00000000000000000
  000000000lt/keygt  
• ltphrase xsitype"xsdstring"gtbritney
  speerslt/phrasegt  
• lt/ns1doSpellingSuggestiongt 
• lt/SOAP-ENVBodygt 
• lt/SOAP-ENVEnvelopegt

47
Example - Google Spelling Response

• lt?xml version"1.0" encoding"UTF-8" ?gt
• ltSOAP-ENVEnvelope xmlnsSOAP
  ENV"http//schemas.xmlsoap.org/soap/envelope/"
• xmlnsxsi"http//www.w3.org/1999/XMLSchem
  a-instance"
• xmlnsxsd"http//www.w3.org/1999/XMLSchem
  a"gt
• ltSOAP-ENVBodygt
• ltns1doSpellingSuggestionResponse
  xmlnsns1"urnGoogleSearch
• SOAP-ENVencodingStyle"http//schemas.xmls
  oap.org/soap/encoding/"gt 
• ltreturn xsitype"xsdstring"gtbritney
  spearslt/returngt  
• lt/ns1doSpellingSuggestionResponsegt 
• lt/SOAP-ENVBodygt 
• lt/SOAP-ENVEnvelopegt

48
An alternative to SOAP XML-RPC

• XML-RPC is similar to SOAP but simpler
• You just have to specify what is the method and
  what are the parameters
• See http//www.xmlrpc.com for further details

49
XML-RPC Request Example

• POST /MyRPC HTTP/1.0
• Host www.cs.huji.ac.il
• Content-Type text/xml
• Content-length 181
• lt?xml version"1.0"?gt
• ltmethodCallgt ltmethodNamegtHello.sayHelloTolt/methodN
  amegt
• ltparamsgt
• ltparamgt
• ltvaluegtltstringgtLisalt/stringgtlt/valuegt
  lt/paramgt
• lt/paramsgt
• lt/methodCallgt

50
XML-RPC Response Example

• HTTP/1.1 200 OK
• Connection close
• Content-Length 158
• Content-Type text/xml
• Date Sun, 6 Jun 2004 103308 GMT
• lt?xml version"1.0"?gt
• ltmethodResponsegt
• ltparamsgt
• ltparamgt
• ltvaluegtltstringgtHello Lisalt/stringgtlt/valuegt
  lt/paramgt
• lt/paramsgt
• lt/methodResponsegt

51
Example 1 MD5 Transform
52
Example 2 Baghdad Weather
53
Example 2 Baghdad Weather
54
Example 3 World Cities
55
Example 3 World Cities
56
WSDL Web Services Description Language
57
Describing a Web Service

• Need a standard way to describe a Web Service
• the methods available
• their parameters
• etc.
• WSDL is a standard for describing Web services
  using XML, i.e., it is a language for the green
  pages of UDDI
• WSDL specification can be found at
  http//www.w3.org/TR/wsdl

58
WSDL Can Describe

• What a Web service can do
• Where it resides
• How to invoke it

59
lt?xml version"1.0"?gt ltdefinitions
name"CurrencyExchangeService"
targetNamespace"http//www.xmethods.net/sd/Curren
cyExchangeService.wsdl" xmlnstns"http//www.x
methods.net/sd/CurrencyExchangeService.wsdl"
xmlnsxsd"http//www.w3.org/2001/XMLSchema"
xmlnssoap"http//schemas.xmlsoap.org/wsdl/soap/"
xmlns"http//schemas.xmlsoap.org/wsdl/"gt
ltmessage name"getRateRequest"gt ltpart
name"country1" type"xsdstring"/gt ltpart
name"country2" type"xsdstring"/gt
lt/messagegt ltmessage name"getRateResponse"gt
ltpart name"Result" type"xsdfloat"/gt
lt/messagegt ltportType name"CurrencyExchangePort
Type"gt ltoperation name"getRate"gt
ltinput message"tnsgetRateRequest"
name"getRate"/gt ltoutput
message"tnsgetRateResponse" name"getRateRespo
nse"/gt lt/operationgtlt/portTypegt
60
ltbinding name"CurrencyExchangeBinding"
type"tnsCurrencyExchangePortType"gt
ltsoapbinding style"rpc" transport"http//schema
s.xmlsoap.org/soap/http"/gt ltoperation
name"getRate"gt ltsoapoperation
soapAction""/gt ltinput name"getRate"gt
ltsoapbody use"encoded" namespace"urnxmethods-
CurrencyExchange"
encodingStyle"http//schemas.xmlsoap.org/soap/enc
oding/"/gt lt/inputgt ltoutput
name"getRateResponse"gt ltsoapbody
use"encoded" namespace"urnxmethods-CurrencyExch
ange" encodingStyle"http//schemas.
xmlsoap.org/soap/encoding/"/gt lt/outputgt
lt/operationgt lt/bindinggt ltservice
name"CurrencyExchangeService"gt
ltdocumentationgtReturns the exchange rate between
the two currencieslt/documentationgt ltport
name"CurrencyExchangePort" binding"tnsCurrencyE
xchangeBinding"gt ltsoapaddress
location"http//services.xmethods.net80/soap"/gt
lt/portgt lt/servicegt lt/definitionsgt
61
The Two Layers of WSDL

• The service definition layer describes abstract
  properties
• data types
• message types
• operations
• services

• The binding layer describes concrete properties
  (using SOAP, HTTP, MIME)
• protocols
• data formats

62
More on the Binding Layer

• WSDL defines services as collections of network
  endpoints or ports
• Endpoints are defined by binding a concrete
  network protocol and a concrete message format to
  abstract operations and messages
• In theory, WSDL can describe any endpoint
  regardless of the underlying network protocol or
  message format
• In practice, WSDL is used with SOAP/HTTP/MIME

63
The Elements of WSDL Documents

• Types containing XML Schema element and type
  definitions
• Message an abstract typed definition of the
  data being communicated
• Operation an abstract description of an action
  supported by the service
• Port Type an abstract set of operations
  supported by one or more endpoints
• Binding a concrete communication protocol and
  data format specification for a particular port
  type
• Port a single endpoint defined as a combination
  of a binding and a network address
• Service a collection of named ports, each
  associated with a binding and a network address

64
The Structure of a WSDL Document

• ltdefinitiongt
• lttypesgt
• definition of types.
• lt/typesgt
• ltmessagesgt
• definition of a message
• lt/messagegt
• ltport typegt
• definition of a port
• lt/port typegt
• ltbindinggt
• definition of a binding
• lt/bindinggt
• lt/definitiongt

ltdefinitiongt
lttypesgt
ltmessagesgt
ltportTypegt
ltbindinggt
65
Example

• lt?xml version"1.0" encoding"UTF-8"?gtltdefinition
  s name"HelloService" targetNamespace"http//w
  ww.hello.com/wsdl/HelloService.wsdl"
  xmlns"http//schemas.xmlsoap.org/wsdl/"
  xmlnssoap"http//schemas.xmlsoap.org/wsdl/soap/"
  xmlnstns"http//www.hello.com/wsdl/HelloServ
  ice.wsdl" xmlnsxsd"http//www.w3.org/2001/XML
  Schema"gt

General and specific namespaces
66
Types

• The lttypesgt element defines the data types that
  are used by the Web service
• For maximum interoperability, WSDL uses XML
  Schema syntax to define data types

67
Messages

• The ltmessagegt element defines the data elements
  of an operation
• Each message can consist of one or more parts
• These parts are analogous to the parameters of a
  function call in Java

68
Example
ltmessage name"SayHelloRequest"gt ltpart
name"firstName" type"xsdstring"/gtlt/messagegtltm
essage name"SayHelloResponse"gt ltpart
name"greeting" type"xsdstring"/gtlt/messagegt
String sayHello(String firstName)
69
Port Types

• The ltportTypegt element is the most important WSDL
  element
• The ltportTypegt element is similar to a class in
  Java
• It defines the Web service, the operations that
  can be performed, and the messages that are
  involved

70
Example
ltportType name"Hello_PortType"gt ltoperation
name"sayHello"gt ltinput message"tnsSayHell
oRequest"/gt ltoutput message"tnsSayHelloRes
ponse"/gt lt/operationgtlt/portTypegt
public interface HelloService public String
sayHello(String firstName)
71
Operation Types

• We divide operations to four types
• One-way the operation can receive a message but
  will not return a response (the operation
  includes only input)
• Request-response the operation can receive a
  request and will return a response (the operation
  includes input and output)
• Solicit-response the operation can send a
  request and will wait for a response (the
  operation includes output and input)
• Notification the operation can send a message
  but will not wait for a response (the operation
  includes only output)

72
Binding Using SOAP

• The SOAP ltbindinggt element defines the details of
  the message format and protocol for each port
• The transport attribute defines the SOAP protocol
  to use (e.g., HTTP, FTP, SMTP)
• The style attribute of the binding can be either
  RPC (Remote Procedure Call) or document (document
  is the default)

73
RPC vs. Document

• RPC style indicates that the messages contain
  parameters and return values
• Document style indicates that the messages
  contain document(s)
• Differently from document style
• In RPC, we need to clearly separate the arguments
  from each other
• In RPC, the order of parameters is important

74
The SOAP Binding in WSDL

• Selects document or rpc style
• Selects HTTP/SMTP/ protocol
• Selects encoding (typically, the SOAP encoding)
• Places messages parts in header or body parts of
  the envelope

75

• ltbinding name"Hello_Binding" type"tnsHello_Port
  Type"gt
• ltsoapbinding style"rpc transport"http//sch
  emas.xmlsoap.org/soap/http"/gt
• ltoperation name"sayHello"gt
  ltsoapoperation soapAction"sayHello"/gt
  ltinputgt ltsoapbody
  encodingStyle"http//schemas.xmlsoap.org/soap/enc
  oding/" namespace"urnexampl
  eshelloservice" use"encoded"/gt
  lt/inputgt ltoutputgt
  ltsoapbody encodingStyle"http//schemas.xmlsoap.o
  rg/soap/encoding/"
  namespace"urnexampleshelloservice"
  use"encoded"/gt lt/outputgt
• lt/operationgt
• lt/bindinggt

76
A Service Description in WSDL(defining an
endpoint)
ltservice name"Hello_Service"gt
ltdocumentationgtWSDL File for HelloServicelt/documen
tationgt ltport binding"tnsHello_Binding"
name"Hello_Port"gt ltsoapaddress
location"http//pita8080/soap/servlet/myService"
/gt lt/portgt lt/servicegt lt/definitionsgt
The location attribute associates the binding
with a URL
77
Recall Currency Exchange Example

• POST http//services.xmethods.net80/soap
  HTTP/1.0
• Content-Type text/xml
• Content-Length 485
• SOAPAction ""
• ltSOAP-ENVEnvelope xmlnsSOAP-ENV"http//schemas.
  xmlsoap.org/soap/envelope/" xmlnsxsi"http//www.
  w3.org/1999/XMLSchema-instance"
  xmlnsxsd"http//www.w3.org/1999/XMLSchema"gt
• ltSOAP-ENVBodygt
• ltns1getRate xmlnsns1"urnxmethods-CurrencyExcha
  nge" SOAP-ENVencodingStyle"http//schemas.xmlsoa
  p.org/soap/encoding/"gt
• ltcountry1 xsitype"xsdstring"gtUnited
  Stateslt/country1gt
• ltcountry2 xsitype"xsdstring"gtIsraellt/country2gt
  
• lt/ns1getRategtlt/SOAP-ENVBodygtlt/SOAP-ENVEnvelopegt

78
CurrencyExchange's WSDL

• Next is the WSDL for this service
• Note that it has to describe
• URL
• URI
• Method Name
• Method Namespace
• Parameter Names
• Parameter Types
• Encoding of Parameters

79
lt?xml version"1.0"?gt ltdefinitions
name"CurrencyExchangeService" targetNamespace"ht
tp//www.xmethods.net/sd/CurrencyExchangeService.w
sdl" xmlnstns"http//www.xmethods.net/sd/Currenc
yExchangeService.wsdl" xmlnsxsd"http//www.w3.or
g/2001/XMLSchema" xmlnssoap"http//schemas.xmlso
ap.org/wsdl/soap/" xmlns"http//schemas.xmlsoap.o
rg/wsdl/"gt ltmessage name"getRateRequest"gt ltpar
t name"country1" type"xsdstring"/gt ltpart
name"country2" type"xsdstring"/gt lt/messagegt lt
message name"getRateResponse"gt ltpart
name"Result" type"xsdfloat"/gt lt/messagegt
80
ltportType name"CurrencyExchangePortType"gt
ltoperation name"getRate"gt ltinput
message"tnsgetRateRequest" /gt ltoutput
message"tnsgetRateResponse" /gt
lt/operationgt lt/portTypegt ltbinding
name"CurrencyExchangeBinding"
type"tnsCurrencyExchangePortType"gt
ltsoapbinding style"rpc"
transport"http//schemas.xmlsoap.org/soap/http"/gt
ltoperation name"getRate"gt ltsoapoperation
soapAction""/gt ltinput gt ltsoapbody
use"encoded" namespace"urnxmethods-CurrencyExc
hange" encodingStyle"http//schemas.xmlsoap.org/
soap/encoding/"/gt lt/inputgt
81
ltoutput gt ltsoapbody use"encoded"
namespace"urnxmethods-CurrencyExchange"
encodingStyle"http//schemas.xmlsoap.org/soap/en
coding/"/gt lt/outputgt lt/operationgt lt/bindinggt lt
service name"CurrencyExchangeService"gt
ltdocumentationgtReturns the exchange rate
lt/documentationgt ltport name"CurrencyExchangePort
" binding"tnsCurrencyExchangeBinding"gt ltsoap
address location"http//services.xmethods.n
et80/soap"/gt lt/portgt lt/servicegtlt/definitionsgt
82
UDDI Universal Description, Discovery and
Integration
83
A Telephone Book

• How can you find a Web service?
• How can you register your Web service so that
  others will find it?
• UDDI is a standard for publishing and finding Web
  services
• Think of UDDI as a telephone book

84
How Does UDDI Work?
UDDI Business Registry
Service Type Registrations
BusinessRegistrations
UDDI assigns a universally unique identifier
(UUID) to each registry record
85
"Types" of Pages

• White Pages
• Basic contact information, business name,
  address, etc.
• Allow others to find you based on your
  identification
• Yellow Pages
• Describe Web services by category
• Allow others to find you by category (e.g., car
  sales)
• Green Pages
• Technical information about supported methods of
  Web services

86
UDDI Data Model
87
UDDI Structure

• businessEntity - The top-level XML element
  (includes support for "yellow pages" taxonomies)
• businessService - contains descriptive business
  service information about a group of related
  technical services, including
• the group name
• a brief description
• technical service-description information
• service properties
• service leasing details
• category information

88
UDDI Structure

• bindingTemplate - contains data relevant for
  applications that need to invoke or bind to a
  specific Web Service
• tModel - Descriptions of specifications
  (protocols, formats, etc.) for Web services or
  taxonomies
• its role is to represent the technical
  specification of the Web service, making it
  easier for Web-service consumers to find Web
  services that are compatible with a particular
  technical specification

89
Key Entities Description
Bindings contain references to tModels. These
references declare the interface specifications
for a service.
0..n
0..n
0..n
90
Key Entities Example
91
Categorizing Entities
92
UDDI Business Registry (UBR), Public Cloud

• Nodes contain all UDDI information
• Nodes are synchronized, so they retain the same
  data
• You can query any node
• You can add UDDI information to a node, and it
  will be replicated to all others

93
Registry Nodes Operation

• Peer-operator nodes
• A business can register with any node
• Registrations replicated on a daily basis
• Operates like DNS logically centralized,
  physically distributed

94
Interacting with the UDDI

• UDDI is itself a Web service!!!
• Interaction is via SOAP messages
• The JAXR package defines a standard way to
  interact with registries (can work with other
  types of registries too, e.g., ebXML)
• Two types of interaction
• Inquiry Does not need authentification
• Publish Needs authentification
• Here is a Web interface for a UBR node

95
JAXR

• Java API used to access registries that conform
  to standards, such as UDDI
• Part of Java WSDP

Taken from http//developer.java.sun.com/developer
/technicalArticles/WebServices/WSPack/
96
UDDI API

• Inquiry API

• Publishing API

• find_business
• find_service
• find_binding
• find_tmodel

• save_business
• save_service
• save_binding
• save_tmodel

• delete_business
• delete_service
• delete_binding
• delete_tmodel

• get_businessDetail
• get_serviceDetail
• get_bindingDetail
• get_tmodelDetail

• get_authtoken
• discard_authtoken