Web Services Description Language (WSDL)

WSDL

^Ø   Web Services Description Language (WSDL)

^Ø   Web Services Description Language (WSDL) is a format for describing a Web Services interface. It is a way to describe services and how they should be bound to specific network addresses. WSDL has three parts:

^ü   Definitions

^ü   Operations

^ü   Service bindings

^Ø   Definitions are generally expressed in XML and include both data type definitions and message definitions that use the data type definitions.

^Ø   These definitions are usually based upon some agreed upon XML vocabulary. This agreement could be within an organization or between organizations.

^Ø   Vocabularies within an organization could be designed specifically for that organization. They may or may not be based on some industry-wide vocabulary.

^Ø   If data type and message definitions need to be used between organizations, then most likely an industry-wide vocabulary will be used.

^Ø   XML, however, is not necessary required for definitions. The OMG Interface Definition Language (IDL), for example, could be used instead of XML.

^Ø   If a different definitional format were used, senders and receivers would need to agree on the format as well as the vocabulary. Nevertheless, over time, XML-based vocabularies and messages are likely to dominate.

^Ø   XML Namespaces are used to ensure uniqueness of the XML element names in the definitions, operations, and service bindings.

^Ø   Operations describe actions for the messages supported by a Web service. There are four types of operations:

^ü    One-way: Messages sent without a reply required

^ü    Request/response: The sender sends a message and the received sends a reply.

^ü    Solicit response: A request for a response. (The specific definition for this action is pending.)

^ü    Notification: Messages sent to multiple receivers. (The specific definition for this action is pending.)

^Ø   Operations are grouped into port types. Port types define a set of operations supported by the Web service.

^Ø   Service bindings connect port types to a port. A port is defined by associating a network address with a port type. A collection of ports defines a service. This binding is commonly created using SOAP, but other forms may be used. These other forms could include CORBA Internet Inter-ORB Protocol (IIOP), DCOM, .NET, Java Message

Service (JMS), or WebSphere MQ to name a few.

The following figure shows the relationship of the basic parts of WSDL: