Lotus Instant Messaging/Web Conferencing (Sametime): Building Sametime Enabled Applications

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

Web services.

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.