The basics

The principles behind web services are stunningly simple, and are nothing new in the world of distributed computing and the Internet:the web service provider defines a format for requests for its service and the response the service will generatea computer makes a request for the web services across the networkthe web service performs some action, and sends the response back

This action might be retrieving a stock quote, finding the best price for a particular product on the net, saving a new meeting to a calendar, translating a passage of text to another language, or validating a credit card number.

Standards support

The reason that we should be suddenly interested in the services model is the incorporation of standard, open protocols for calling services and transmitting data.

While in the past many data and service providers have had proprietary standards or rough and ready data formats, we can now rely on simple  (XML) based access over plain old HTTP. This means easier access and should let developers working with all sorts of technologies start playing the web services game.

The difference between web services and technologies developers have used in the past like DCOM, named pipes, and RMI, is that most web services rely on open standards, are relatively easy to command, and have widespread support across the Unix / Windows divide.