What is WSDL document?

As communications protocols and message formats are standardized in the web community, it becomes increasingly possible and important to be able to describe the communications in some structured way. WSDL addresses this need by defining an XML grammar for describing network services as collections of communication endpoints capable of exchanging messages. WSDL service definitions provide documentation for distributed systems and serve as a recipe for automating the details involved in applications communication.

A WSDL document defines services as collections of network endpoints, or ports. In WSDL, the abstract definition of endpoints and messages is separated from their concrete network deployment or data format bindings. This allows the reuse of abstract definitions: messages, which are abstract descriptions of the data being exchanged, and port types which are abstract collections of operations. The concrete protocol and data format specifications for a particular port type constitutes a reusable binding. A port is defined by associating a network address with a reusable binding, and a collection of ports define a service. Hence, a WSDL document uses the following elements in the definition of network services:

• Types– a container for data type definitions using some type system (such as XSD).
• Message– an abstract, typed definition of the data being communicated.
• Operation– an abstract description of an action supported by the service.
• Port Type–an abstract set of operations supported by one or more endpoints.
• Binding– a concrete protocol and data format specification for a particular port type.
• Port– a single endpoint defined as a combination of a binding and a network address.
• Service– a collection of related endpoints.

These elements are described in detail in Section 2. It is important to observe that WSDL does not introduce a new type definition language. WSDL recognizes the need for rich type systems for describing message formats, and supports the XML Schemas specification (XSD) [11] as its canonical type system. However, since it is unreasonable to expect a single type system grammar to be used to describe all message formats present and future, WSDL allows using other type definition languages via extensibility.

In addition, WSDL defines a common binding mechanism. This is used to attach a specific protocol or data format or structure to an abstract message, operation, or endpoint. It allows the reuse of abstract definitions.

In addition to the core service definition framework, this specification introduces specific binding extensions for the following protocols and message formats:

• SOAP 1.1
• HTTP GET / POST
• MIME

Although defined within this document, the above language extensions are layered on top of the core service definition framework. Nothing precludes the use of other binding extensions with WSDL.

What is WSDL document?

As communications protocols and message formats are standardized in the web community, it becomes increasingly possible and important to be able to describe the communications in some structured way. WSDL addresses this need by defining an XML grammar for describing network services as collections of communication endpoints capable of exchanging messages. WSDL service definitions provide documentation for distributed systems and serve as a recipe for automating the details involved in applications communication.

A WSDL document defines services as collections of network endpoints, or ports. In WSDL, the abstract definition of endpoints and messages is separated from their concrete network deployment or data format bindings. This allows the reuse of abstract definitions: messages, which are abstract descriptions of the data being exchanged, and port types which are abstract collections of operations. The concrete protocol and data format specifications for a particular port type constitutes a reusable binding. A port is defined by associating a network address with a reusable binding, and a collection of ports define a service. Hence, a WSDL document uses the following elements in the definition of network services:

• Types– a container for data type definitions using some type system (such as XSD).
• Message– an abstract, typed definition of the data being communicated.
• Operation– an abstract description of an action supported by the service.
• Port Type–an abstract set of operations supported by one or more endpoints.
• Binding– a concrete protocol and data format specification for a particular port type.
• Port– a single endpoint defined as a combination of a binding and a network address.
• Service– a collection of related endpoints.

These elements are described in detail in Section 2. It is important to observe that WSDL does not introduce a new type definition language. WSDL recognizes the need for rich type systems for describing message formats, and supports the XML Schemas specification (XSD) [11] as its canonical type system. However, since it is unreasonable to expect a single type system grammar to be used to describe all message formats present and future, WSDL allows using other type definition languages via extensibility.

In addition, WSDL defines a common binding mechanism. This is used to attach a specific protocol or data format or structure to an abstract message, operation, or endpoint. It allows the reuse of abstract definitions.

In addition to the core service definition framework, this specification introduces specific binding extensions for the following protocols and message formats:

• SOAP 1.1 (see Section 3)
• HTTP GET / POST (see Section 4)
• MIME (see Section 5)

Although defined within this document, the above language extensions are layered on top of the core service definition framework. Nothing precludes the use of other binding extensions with WSDL.

Web Services in Lotus Notes

There are new things added, and most of us are not came across those special changes. Web services in Lotus notes is one of such changes. With the release of Lotus Notes 7, they have added the facility to create and access the web services with the Lotus Notes.

A Web service is an archive of remote operations that can be called by sending messages over the Internet. A Web service provider publishes a Web service for query and use, and a Web service consumer calls operations from the service. A Web service provider makes available a WSDL (Web Services Description Language) document that defines the service interface. The WSDL document is in XML format. What happens behind the interface is up to the provider, but most providers map the interface to procedure calls in a supported programming language. Incoming requests from a consumer are passed through to the underlying code, and results are passed back to the consumer.
Lotus Domino maps the WSDL interface to an agent-like Web service design element that can be coded in LotusScript or Java. To be used, the Web service must be on a Domino server with HTTP enabled. (We can test the Web service through an HTTP session in the Notes client preview.)

Access is through one of the following Domino URL commands:

?OpenWebService invokes the Web service in response to a SOAP-encoded message sent through an HTTP POST. An HTTP GET (for example, a browser query) returns the name of the service and its operations.

?WSDL returns the WSDL document in response to an HTTP GET.

Several approaches are possible for creating a Web service design element in Domino Designer. We can code it entirely in LotusScript or Java. In these cases, saving the design element generates a WSDL document that reflects the LotusScript or Java code. Or we can import an existing WSDL document. In this case, LotusScript or Java is generated that reflects the operations in the imported WSDL. The Web service design element saves the WSDL document as well as the code. If the public interface has not changed, the WSDL document stays as is. If, in our coding, we change anything that affects the public interface, a new WSDL is generated.

In Domino Designer, the Web service design element resides below Agents under Shared code. The Web service design window looks a lot like the agent design window. Click the New Web Service button to create a new Web service. Double-click an existing Web service to edit it.