SOAP / XML based Web Services

A Web Service is programmable application logic accessible via standard Web protocols. One of these Web protocols is the Simple Object Access Protocol (SOAP). SOAP uses standards based on technologies (XML for data description and HTTP for transport) to encode and transmit application data.
Consumers of a Web Service do not need to know anything about the platform, object model, or programming language used to implement the service; they only need to understand how to send and receive SOAP messages (HTTP and XML).

Why Web services

Web services, a major new trend in standards-based software technology, is made up of pieces of custom-developed code that lets two or more applications talk to each other. Those services can pull a single piece of data (such as a stock quote) or an entire business process (such as checking a customer’s credit and giving him a credit score).

Web services can help companies integrate disparate systems for less money than traditional methods. Previous solutions have helped companies exchange data for years, but it lacks flexibility and is costly to maintain. And where an enterprise application integration package can run into the hundreds of thousands of dollars, Web services that can meet comparable business goals can be built for tens of thousands of dollars.

How it is useful?

A Single web service can be used by many other applications. With web services your accounting department’s Win 2k servers can connect with your IT supplier’s UNIX server.
Web services enable us to connect many more applications and devices having fully different platform and operating system.

An airline company can share its up to date data of its all the flights with its many travel agents, partner agencies, connected airports and even to the Black Berry of his customer!
Using Web services, amazone.com can plan to make forecasts and reports instantly available to its drop-ship vendors so that they can better match supplies with the company’s demands.
All of them will do have different platform and application to work with but it becomes very easy to connect them all with web services.