Overview

Web Services are a recent technology innovation for the World Wide Web. Simply put, a Web Service is a Web-based application program with a defined interface that accepts and processes requests and returns a response back to the requester. A Web Service is not directly bound to a specific requesting application (e.g., a Web Service is "loosely coupled"). In some respects, a Web Service is similar to a client server model, where the Web Service is a server. However, a Web Service is a platform agnostic program that is accessible from the Web. The characteristics of a Web Service include the following:

• The Web Service supports common methods of invocation.

• The interface for a Web Service is generally platform agnostic.

• The method of internal implementation for a Web Service is generally unknown by the requester (i.e., the client).

• The functionality provided by a Web Service implies a context but is not restricted to use by any single application or application type.

Although not a restriction, a typical (external) Web Service operates across the World Wide Web. Almost any communication protocol or form of messaging can be used for invocation (e.g., a Web Service is interoperable). Currently, the most common protocol is HyperText Transmission Protocol (HTTP), but this is not a restriction. In fact a Web Service could be invoked using File Transfer Protocol (FTP), Remote Procedure Call (RPC), or similar methods. The obvious advantage of interoperability is that applications using HTTP to transport information can be readily adapted...