WSDL

What is WSDL?

WSDL is stands for Web Services Description Language.Basically WSDL is fully based on XML.Main use of WSDL to describe the web services and also told how to use this web services.It is written on XML. Also WSDL has W3C Recommendation Since 26 June 2007.

How you define WSDL document?

  WSDL given us many element to describe its document. I have only given you four elements which are main elements to describing WSDL document.
These are:

<portType> is an important element to describe WSDL document.Using this element we can perform a task to compare a function library(like: class) in traditional programming language.

each <message> element has more than one parts.we can compare that parts.

using <types> we can define datatypes that are used in web services.

using <binding> for each port we can define the format of messages and details of protocol.

Syntax:
<definitions>
<types>
   To define type here
</types>
<message>
   To define message here
</message>
<portType>
   To define portType here
</portType>
<binding>
   To define binding here
</binding>
</definitions>

How you define Binding in WSDL?

 Basically we use binding in WSDL to define format of messages and detailed information about protocol of web services.
I have given you binding consist of two attributes.These are name attribute and type attribute(name is used to define binding name where as type is used to define binding port.

 I case of SOAP binding it has two attribute. These are style and transport attribute.
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>
<binding type=\"glossaryTerms\" name=\"b1\">
<soap:binding style=\"document\"
transport=\"http://xyzsoap.org/soap/http\" />
  <operation>
    <soap:operation
     soapAction=\"http://soapexample.com/getTerm\"/>
    <input>
      <soap:body use=\"literal\"/>
    </input>
    <output>
      <soap:body use=\"literal\"/>
    </output>
  </operation>
</binding>

What is WSDL and disco file ?

WSDL: Files with the WSDL extension contain web service interfaces expressed in the Web Service Description 
Language (WSDL). WSDL is a standard XML document type specified by the World Wide Web Consortium.

WSDL files are used to communicate interface information between web service producers and consumers. A WSDL description allows a client to utilize a web service?s capabilities without knowledge of the implementation 
details of the web service.


Disco: It is a Microsoft technology for publishing and discovering Web Services. DISCO can define a document 
format along with an interrogation algorithm, making it possible to discover the Web Services exposed on a given 
server. DISCO makes it possible to discover the  capabilities of each Web Service (via documentation) and 
how to interact with it. To publish a deployed Web Service using DISCO, you simply need to create a .disco file and 
place it in the vroot along with the other service-related configuration.

What is the history of the WSDL?

WSDL 1.1 was submitted as a W3C Note by Ariba, IBM and Microsoft for describing services for the W3C XML Activity on XML Protocols in March 2001.WSDL 1.1 has not been endorsed by the World Wide Web Consortium (W3C), however it has just (May 11th, 2005) released a draft for version 2.0, that will be a recommendation (an official standard), and thus endorsed by the W3C.

How WSDL Works in the World of Java Technology?

The Web service is registered in a UDDI repository using the Java API for XML Registries (JAXR), where a business partner or other system can find the service. The registry information from UDDI is used to locate a WSDL document that details the call semantics for the Web service. With the WSDL document in hand, the Java programmer can then feed it to a tool that can generate a Java object proxy to the Web service, or simply use it as a reference document along with a lower-level SOAP API.

What is the Disadvantage of WSDL?

1. Only one web service operation per WSDL.
Embedded schemas don\'t allow modularization of WSDL by importing XML schemas into the types section.
Because of 1 and 2, no ability to reuse XML schema definitions across operations.
No control over generated \"container\" message type names.

What is the advantages of WSDL?

WSDL to Java:

1. Convenient when WSDL document already exists
2. More powerful
3. Requires WSDL and XML Schema knowledge
4. Easy to stray outside of WS-I BP 1.0, harming interoperability 

Java to WSDL:

1. Easy to use
2. No need to learn WSDL or XML Schema
3. Less control over published service contract

What is the Simple Structure Of WSDL Program?

<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>