84 Lotus Instant Messaging/Web Conferencing (Sametime): Building Sametime-Enabled Applications
4.1 Overview of Web services
As you may already be well aware, Web services have gained tremendous
interest and coverage in the IT industry in recent years. There have been many
books published on the topic, so we do not attempt to cover the complete
spectrum of Web services in this chapter. We do, however, give a brief
introduction, so you may gain an understanding as to why you may want to use
4.1.1 What is a Web service?
A widely accepted definition for a Web service is:
“A self-contained, self-describing, modular application that can be published,
located and invoked across the Web.”
Web services enable the creation of applications that navigate, discover, and use
other applications, in much the same way that people navigate, discover, and
use Web sites and Web-based business applications.
With Web services, any business system can expose its underlying functionality
in new ways. A Web services layer allows developers to easily and dynamically
incorporate that system’s functionality in any application, regardless of the
language it is written in or the platform it runs on. Once a Web service is
deployed, other applications (and other Web services) can discover and invoke
the deployed service. The Web services model shifts the focus to integrating
applications, independent of platform, language, or data structure.
4.1.2 Web service fundamentals
Web services are built on the foundation of two technologies:
XML: The universal language for data description. XML’s separation of
content and presentation allows data to be manipulated in a reliable,
automated way. Instructions or content represented by XML can be
understood by any application that supports XML.
SOAP: The Simple Object Access Protocol uses XML messages to invoke
remote methods. A Web service could interact with remote machines through
HTTP’s POST and GET methods, but SOAP is much more robust and flexible.
In a typical Web services scenario, a business application sends a request to a
service at a given URL using the SOAP protocol over HTTP. The service receives
the request, processes it, and returns a response.