WSDL Web Services Description Language

1
WSDL Web Services Description Language

• Neet Wadhwani
• University of Colorado
• 3rd October, 2001

2
Overview

• Introduction
• Definitions
• Working of WSDL
• SOAP Binding
• HTTP GET POST Binding
• MIME Binding
• References

3
Introduction

• WSDL is an XML language that contains information
  about the interface semantics and administrivia
  of a call to a Web Service
• Once you develop a Web Service you publish its
  description and a link to it in a UDDI repository
  so that potential users can find it
• When someone wants to use your service, they
  request the WSDL file in order to find out the
  location of the service, the function calls and
  how to access them
• Then they use this information in your WSDL file
  to form a SOAP request to the computer

4
Definitions

• Definitions
• - WSDL is an XML-based language used to
• define Web Services and describe how to
• access them.
• - WSLD is an XML format for describing
• network services as a set of endpoints
• operating on messages containing either
• document-oriented or procedure-oriented
• information.

5
Working of WSDL

Figure 1. A client invoking a Web service.
6
Working of WSDL contd.

Figure 2. WSDL terminology used for describing
Web services.
7
Working of WSDL (with Java) contd.

8
Working of WSDL contd.

• A client can invoke a web service using SOAP,
  HTTP GET/POST and MIME.
• WSDL Document Structure
• ltdefinitiongt - Root element
• lttypesgt - Provides data type definitions
• ltmessagegt - Represents the abstract definition of
  the data being transmitted
• ltportTypegt - Defines a set of abstract operations
• ltbindinggt - Specifies concrete protocol and data
  format specifications for the operations and
  messages defined by a particular portType
• ltportgt - Specifies an address for a binding
• ltservicegt - Used to aggregate a set of related
  ports.

9
Namespace

• The XML namespace prefix are used to indicate the
  namespace of the element being defined
• All WSDL elements belong to the WSDL namespace,
  defined as http//schemas.xmlsoap.org/wsdl/
• For WSDL SOAP binding,
• http//schemas.xmlsoap.org/wsdl/soap/
• For WSDL HTTP GET and POST binding,
• http//schemas.xmlsoap.org/wsdl/http/
• For WSDL MIME binding,
• http//schemas.xmlsoap.org/wsdl/mime/

10
Service

• A service groups a set of related ports together
• Let is consider an example of a Web Service and
  the GetTemperature method as an operation on that
  service.
• ltdefinitions nameweatherservice
• xmlnshttp//schemas.xmlsoap.org/wsdl/gt
• lttypegt
• ltxsdschema /gt
• lt/typegt
• ltservice nameWeatherService gt
• lt/servicegt
• lt/definitionsgt

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Port

• A port defines an individual endpoint by
  specifying a single address for a binding
• ltport nameWeatherSoapPort bindingwsdlnsWeath
  erSoapBinding gt
• ltsoapaddress
• locationhttp//localhost/demos/wsdl/devx pert/
  weatherservice.asp /gt
• lt/portgt
• Each port has a unique name and a binding
  attribute
• A web service may be accessible on many ports
• A port MUST NOT specify more than one address
• A port MUST NOT specify any binding information
  other than address information

12
Message

• A message is protocol independent
• There is an input or request message, which is
  sent from the client to the service, and there is
  a output or response message, which is sent back
  the opposite way
• Each ltmessagegt element contains one or more
  ltpartgt elements.
• ltpartgt element corresponds to the parameter or a
  return value in the RPC call.
• The part name order reflects the order of the
  parameters in the RPC signature.

13
Message contd.

• ltmessage nameWeather.GetTemperature gt
• ltpart namezipcode typexsdstring /gt
• ltpart namecelsius typexsdboolean /gt
• lt/messagegt
• ltmessage nameWeather.GetTemperatureResponse gt
• ltpart nameResult typexsdfloat /gt
• lt/messagegt

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Operations and PortType

• Operation defines which message is the input and
  which message is the output
• A collection of all operations exposed bythe web
  service is called a portType
• ltportType nameWeatherSoapPortgt
• ltoperation nameGetTemperature
  parameterOrderzipcode celsiusgt
• ltinput messagewsdlnsWeather.GetTemperature
  /gt
• ltoutput messagewsdlnsWeather.GetTemperatureRe
  sponse /gt
• lt/operationgt
• lt! other operations ?
• lt/portTypegt

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Operations and PortType

• WSDL has four transmission primitives that an
  endpoint can support
• One-Way The endpoint receives a message
• ltwsdlinputgt
• Request-response The endpoint receives a
• message and sends a correlated message
• ltwsdlinputgt,ltwsdloutputgt,ltwsdlfaultgt
• Solicit-response The endpoint sends a message
  and receives a correlated message
• ltwsdloutputgt, ltwsdlinputgt, ltwsdlfaultgt
• Notification The endpoint sends a message
• ltwsdloutputgt

16
Binding

• Binding mechanism is used to attach a specific
  protocol, data format or structure to an abstract
  message , operation or endpoint
• Binding MUST specify exactly one protocol
• Binding MUST NOT specify address information
• Extensibility elements are commonly used to
  specify some technology specific binding
• ltbinding nameWeatherSoapBinding
  typewsdlnsWeatherSoapPort gt
• lt/bindinggt

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SOAP Binding

• ltsoapbindinggt - Signifies that the binding is
  bound to the SOAP protocol format Envelope,
  Header and Body
• ltbinding gt
• ltsoapbinding transporturi?
  Stylerpcdocument?gt
• lt/bindinggt
• ltsoapoperationgt - Provides information for the
  document as a whole
• ltbinding gt
• ltoperation gt
• ltsoapoperation soapActionuri?
  Stylerpcdocument?gt
• lt/operationgt
• lt/bindinggt

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SOAP Binding contd.

• ltsoapbodygt - Specifies how the message parts
  appear inside the SOAP Body element
• ltinputgt
• ltsoapbody partsnmtokens? useliteralencoded
  ?
• encodingStyleuri-list? Namespaceuri?gt
• lt/inputgt
• ltsoapfaultgt - Specifies the contents of the
  contents of the SOAP fault
• ltfaultgt
• ltsoapfault namenmtoken useliteralencoded
  encodingStyleuri-list? Namespaceuri?gt
• lt/faultgt

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SOAP binding contd.

• ltsoapheadergt and ltsoapheaderfaultgt - Allow
  headers to be defined that are transmitted inside
  the Header element of the SOAP Envelope
• ltinputgt
• ltsoapheader messageqname partnmtoken
  useliteralencoded? encodingStyleuri-list?
  Namespaceuri?gt
• ltsoapheaderfault messageqname partnmtoken
  useliteralencoded? encodingStyleuri-list?
  Namespaceuri?gt
• lt/inputgt
• ltsoapaddressgt - Used to give a port an address
  (a URI)
• ltbinding gt
• ltsoapaddress locationuri /gt
• lt/bindinggt

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HTTP GET POST Binding

• lthttpaddressgt - Specifies the base URI for the
  port
• lthttpbindinggt - Indicates that this binding uses
  the HTTP protocol
• ltbinding gt
• lthttpbinding verbnmtoken /gt
• lt/bindinggt
• lthttpoperationgt - has an attribute that
  specifies the relative URI for the operation
• ltoperation gt
• lthttpoperation locationuri /gt
• lt/operationgt

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HTTP GET POST Binding contd.

• lthttpurlEncodedgt - Indicates that all the parts
  are encoded into the HTTP request URI using the
  standard URI-encoding rules
• lthttpurlReplacementgt - Indicates that all the
  message parts are encoded into the HTTP request
  URI using a replacement algorithm

22
MIME Binding

• ltmimecontentgt - Used if there is no additional
  information to convey about the format other than
  its MIME type string
• ltmimecontent partnmtoken? Typestring? /gt
• ltmimemultipartRelatedgt - Aggregates an arbitrary
  set of MIME formatted parts into one message
  using the MIME type multipart/related
• ltmimemultipartRelatedgt
• ltmimepartgt
• ? mime element ?
• lt/mimepartgt
• lt/mimemultipartRelatedgt

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MIME Binding contd.

• ltsoapbodygt - When using the MIME binding with
  SOAP requests, it is legal to use the soapbody
  element as a MIME element. It indicates the
  content type is text/xml, and there is an
  enclosing SOAP Envelope
• ltmimemimeXmlgt - Used to specify a concrete
  schema
• ltmimemimeXml partnmtoken? /gt

24
References

• World Wide Web Consortium
• http//www.w3c.org/TR/wsdl
• DevXpert
• http//www.devxpert.com/tutors/wsdl/wsdlprint.asp
  
• Sun Java Website
• http//dcb.sun.com/practices/webservices/overview
  s/overview_wsdl.jsp