18. Web Services

Abstract

The term Web Services describes an application of XML for exposing application functionality to disparate clients via the Web. This paradigm provides access to entire applications, modules, objects, functions, and methods via HTTP and other transport protocols. Web Services are inherently platform- and programming-language independent. Services can be developed in one language and consumed in another; this holds true irrespective of client or server host operating system combinations.

A collection of core XML-based specifications and standards work in concert to fulfill the Web services value proposition. These standards include:

• SOAP - XML notation that describes how messages are assembled and transmitted over HTTP between services and service consumers.
• WSDL - XML notation for describing SOAP services.
• UDDI - Application of the SOAP protocol for registering and publishing information about organizations, contacts within organizations, and Web Services that these organizations have chosen to expose to the public.

Virtuoso enables stored procedures to be exposed as Web services that are consumable by any Web services-aware development tool, application, or environment. The stored procedures exposed by Virtuoso may be native stored procedures, or may be hosted in any third-party database that supports stored procedures, and is accessible via an ODBC or JDBC driver. In Virtuoso, exposing stored procedures as Web services does not require any programming effort. You simply identify the stored procedures to be exposed using the Virtuoso Administrative Interface.

This feature is immensely valuable in situations where organizations are seeking to transform time-tested stored procedures into Web Services without having to upgrade or change databases or host operating systems. In modern enterprises, such stored procedures drive mission-critical solutions; Virtuoso's approach to Web services enables you to maximize current investment while minimizing the need for rework.