If you are doing anything related to Internet technology you will hear the term "Web Service" used. This is a three minute explanation of what a Web Service is and why it is important.

You know what a Web Site is: a collection of web pages and other resources that provide and store information using the Internet. We interact with Web Sites via a browser (like Internet Explorer) and web server software (like Microsoft Internet Information Server.) You also know that being able to obtain and share information using the above technology has significantly changed the World.

Well, if Web Service technology fulfils the goals of its designers, it will have a major impact on the Internet and on how information systems of the near future are developed.

Here is the essential idea: Web Sites are for Humans Web Services are for Programs.

The intent of Web Services is to permit development of distributed information systems using standard Internet technologies. Over the years several approaches to programming distributed system have been developed and these have been very successful. But, the phenomenon of the Internet has caused programmers to look to new ways of developing systems that can leverage the ubiquitous Internet infrastructure. Therefore, Web Services have been designed to use standard Internet technology and, if successful, may have as big an impact on information sharing as the browser.

Here is an example. Imagine an auto parts distributor's web site with a catalogue of parts and a shopping cart facility for on-line ordering. This works well but is limited to the number of buyers that know about the site. With a bit of programming using Web Services technology, the existing catalogue can be offered to programs that search the Internet for parts, can read catalogue and place orders directly. Other Web Services offering shipping prices, credit card processing, etc., can be combined with the auto parts catalogue Web Service to build smart distributed applications for the buyer.

Industry groups are working on standards to represent their business information formats such as a car part, credit card information and so on for use by Web Services. As these information standards and Web Services technologies mature a new level of Internet functionality will evolve.

Finally, let's take a brief look at the underlying technology that makes Web Services so compelling.

XML stands for eXtensible Markup Language. XML is a standard for defining documents for exchange between programs over the Internet. The power of XML lies in the fact that it is a language for defining languages: a meta-language. Everything about Web Services is expressed in XML. The industry standards mentioned above are specified in XML, the messages that Web Services send back and forth are in XML, and the details of Web Services themselves are specified in XML.

The message format or envelope that Web Services use is called Simple Object Access Protocol or SOAP. Of course, SOAP is specified using XML. SOAP messages invoke functions that get or deposit data on the server. These SOAP messages are sent using HTTP (Hypertext Transport Protocol). This is the same protocol that web browsers use to fetch web pages. Now you see how Web Services fit in with the Internet.

There is a lot more to the technology and it is moving fast. For example, Microsoft's .NET technology and strategy is based on XML and Web Services. The main thing to remember from this article is that the term Web Service means a specific technology that permits opening up all the content on the Web to access by programs in a simple way. If it works out it will represent a next stage in the evolution of the Internet.