Webservice FAQS

* Web services are application components
* Web services communicate using open protocols
* Web services are self-contained and self-describing
* Web services can be discovered using UDDI
* Web services can be used by other applications
* XML is the basis for Web services

How Does it Work?

The basic Web services platform is XML + HTTP.

XML provides a language which can be used between different platforms and programming languages and still express complex messages and functions.

The HTTP protocol is the most used Internet protocol.

Web services platform elements:

* SOAP (Simple Object Access Protocol)
* UDDI (Universal Description, Discovery and Integration)
* WSDL (Web Services Description Language)

Interoperability has Highest Priority

When all major platforms could access the Web using Web browsers, different platforms could interact. For these platforms to work together, Web-applications were developed.

Web-applications are simple applications that run on the web. These are built around the Web browser standards and can be used by any browser on any platform.
# Web Services take Web-applications to the Next Level

By using Web services, your application can publish its function or message to the rest of the world.

Web services use XML to code and to decode data, and SOAP to transport it (using open protocols).

With Web services, your accounting department's Win 2k server's billing system can connect with your IT supplier's UNIX server.
# Web Services have Two Types of Uses

Reusable application-components.

There are things applications need very often. So why make these over and over again?

Web services can offer application-components like: currency conversion, weather reports, or even language translation as services.

Connect existing software.

Web services can help to solve the interoperability problem by giving different applications a way to link their data.

With Web services you can exchange data between different applications and different platforms.

WSDL

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 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 element can be compared to a function library (or a module, or a class) in a traditional programming language.
# WSDL Messages

The 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 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 element defines the message format and protocol details for each port.

A WSDL port describes the interfaces (legal operations) exposed by a web service.
# WSDL Ports

The element is the most important WSDL element.

It defines a web service, the operations that can be performed, and the messages that are involved.

The port defines the connection point to a web service. It can be compared to a function library (or a module, or a class) in a traditional programming language. Each operation can be compared to a function in a traditional programming language.
# Operation Types

The request-response type is the most common operation type, but WSDL defines four types:
Type Definition
One-way The operation can receive a message but will not return a response
Request-response The operation can receive a request and will return a response
Solicit-response The operation can send a request and will wait for a response
Notification The operation can send a message but will not wait for a response
# One-Way Operation

A one-way operation example:











In the example above, the port "glossaryTerms" defines a one-way operation called "setTerm".

The "setTerm" operation allows input of new glossary terms messages using a "newTermValues" message with the input parameters "term" and "value". However, no output is defined for the operation.
# Request-Response Operation

A request-response operation example:

In the example above, the port "glossaryTerms" defines a request-response operation called "getTerm".

The "getTerm" operation requires an input message called "getTermRequest" with a parameter called "term", and will return an output message called "getTermResponse" with a parameter called "value".