IBM Version 5 manual Web services and XML

XSLT has become a critical part of Web applications, because it allows versatility in the presentation logic. W3C has published a working draft for XSLT Version 2.0 and XML Path Language (XPath) Version 2.0 in April 2002. The later had a major IBM involvement.

1.8 Web services and XML

Web services have gained prominence in the last three years. They are the new middleware that will glue all kinds of disparate applications from different vendors. Presently, there are a few major vendors touting middleware: TIBCO, BEA eLink/Tuxedo and IBM’s MQ-series. Web services on the other hand are not proprietary. They are self-contained, modular applications, self explanatory applications that are published on the Web. They provide functions that encapsulate anything from single functions to complex business functions. An example of a simple function may be a calculator, spreadsheet, or a tutorial. An example complex functions could be the processing of a tax return, stock quotes, or processing credit card transactions. Once this Web service has been deployed, anyone (be it another application or Web service) would be able to locate and invoke it.

When we discuss Web services, we involve a few components:

Simple Object Access Protocol (SOAP) is an XML-based protocol that allows applications to invoke applications provided by service provides anywhere on the Web. It is supported by HTTP, and therefore, can be run on the Internet without any new requirements over existing infrastructure. It is independent off any programming language and component technology, and is object neutral. It is also independent of operating systems.

Universal Description Discovery and Integration (UDDI) is a specification for Web registries of Web services. Web users locate and discover services on a UDDI-based registry. There are registries of services distributed over the Internet, and these registry of services are described in a common XML format or schema. For a common format, searching and analysis of applications would be made much easier. A UDDI registry has been made available from IBM’s alphaWorks Web site, and supports users in various department- or company-wide scenarios.

Web Services Description Language (WSDL) is a language that is used to describe a service to the world. The definition of WSDL is:

“WSDL is an XML format for describing network services as a set of end-points operating on messages containing either document-oriented or procedure-oriented information. The operations and messages are described abstractly, and then bound to a concrete network protocol and message

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