WebSphere Message Brokers
File: ac55750_
Writer: Michael Gibson

Concept topic

This build: July 31, 2007 21:21:11

Web services description

A Web service description is a document that the service provider uses to communicate the specifications for starting the Web service to the service requester. Web service descriptions are expressed in the XML application known as Web Service Description Language (WSDL).

The service description describes the Web service in such a way so as to minimize the amount of shared knowledge and customized programming that is needed to ensure communication between the service provider and the service requester. For example, neither the requester nor the provider needs to be aware of the platform on which the other runs, nor of the programming language in which the other is written.

A service description can conform to either the WSDL 1.1 or WSDL 2.0 specification, and there are differences in both the terminology and major elements that can be included in the service description. WebSphere Message Broker supports WSDL 1.1 only. The following information uses WSDL 1.1 terminology and elements to explain the purpose of the service description.

The structure of WSDL allows a service description to be partitioned into:

A WSDL 1.1 document uses the following major elements in the definition of network services:
<types>
A container for data type definitions using some type system (such as XML Schema). Defines the data types used within the message. The <types> element is not required when all messages consist of simple data types.
<message>
Specifies which XML data types are used to define the input and output parameters of an operation.
<portType>
Defines the set of operations supported by one or more endpoints. Within a <portType> element, each operation is described by an <operation> element.
<operation>
Specifies which XML messages can appear in the input and output data flows. An operation is comparable with a method signature in a programming language.
<binding>
Describes the protocol, data format, security and other attributes for a particular <portType> element.
<port>
Specifies the network address of an endpoint, and associates it with a <binding> element.
<service>
Defines the Web service as a collection of related endpoints. A <service> element contains one or more <port> elements.
Draft comment:
Insert Figure 1. Structure of a Web service description

Figure 1. Structure of a Web service description

The ability to partition the Web service description makes it possible to divide responsibility for creating a complete service description. As an illustration, consider a service which is defined by a standards body for use across an industry, and implemented by individual companies within that industry:
Related concepts
Service publication
Web services architecture
WSDL Version 1.1
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This build: July 31, 2007 21:21:11

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