WSDL Documents
A WSDL document is just a simple XML document.
It contains set of definitions to describe a web service.
The WSDL Document Structure
A WSDL document describes a web service using these major elements:
| Element |
Defines |
| <types> |
The data types used by the web service |
| <message> |
The messages used by the web service |
| <portType> |
The operations performed by the web service |
| <binding> |
The communication protocols used by the web service |
The main structure of a WSDL document looks like this:
<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> |
A WSDL document can also contain other elements, like extension elements, and a service element that makes it possible to group together the definitions of
several web services in one single WSDL document.
WSDL Ports
The <portType> element is the most important WSDL element.
It describes a web service, the operations that can be performed, and the messages that are involved.
The <portType> element can be compared to a function library (or a module, or a class)
in a traditional programming language.
WSDL Messages
The <message> element defines the data elements of an operation.
Each message can consist of one or more parts. The parts can be compared
to the parameters of a function call in a traditional programming language.
WSDL Types
The <types> element defines the data types that are used by the web service.
For maximum platform neutrality, WSDL uses XML Schema syntax to define data types.
WSDL Bindings
The <binding> element defines the message format and protocol details for each port.
WSDL Example
This is a simplified fraction of a WSDL document:
<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> |
In this example the <portType> element defines "glossaryTerms"
as the name of a port, and "getTerm" as the name of an operation.
The "getTerm" operation has an input message called "getTermRequest"
and an output message called "getTermResponse".
The <message> elements define the parts of each message and
the associated data types.
Compared to traditional programming, glossaryTerms is a function library, "getTerm"
is a function with "getTermRequest" as the input parameter, and getTermResponse as
the return parameter.
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