INTERACTIVE WEB SERVICES WITH JAVA

The WSDL Language

The language can be described as having two layers:

the service definition layer describes abstract properties:
- data types
- message types
- operations
- services
the binding layer describes concrete properties:
- protocols
- data formats
(using SOAP, HTTP, MIME)

An actual WSDL document consists of a set of definitions of the following kinds:

types - containing XML Schema element and type definitions
message - consisting of either
- a number of named parts typed by XML Schema elements, or
- a single part typed by a XML Schema type
portType - describing a set of operations, each being either
- one-way: receiving an input message,
- request-response: receiving an input message and then responding with an output message (like Remote Procedure Calls),
- solicit-response: sending an output message and then receiving an input message, or
- notification: sending an output message
binding - selects communication protocol and data formats for each operation and message
service - describes a collection of named ports, each associated with a binding and a network address

An import mechanism allows modularization of definitions.

(Unfortunately, the binding layer is quite loosely specified...)