Anecdotal evidence has it that the first time web services, in the context of XML-structured messages, were mentioned by Bill Gates was at the Microsoft Professional Development Conference in Orlando, Florida, on July 12, 2000. By that time, many organizations, including Microsoft, Sun, and IBM, had been working on XML Schema and SOAP specifications. Don Box, in his article named Brief History of SOAP, (http://www.xml.com/pub/a/ws/2001/04/04/soap.html) presents an excellent overview of issues, more political than technical, surrounding that development.

The invention of XML was critical to web services development. Electronic Data Interchange (EDI), which dominated the market at that time, presented a quite complex data exchange format. Also, despite the fact that it was published as a standard, EDI was influenced by virtually every software vendor that used it. XML looked much simpler and more generic.

The concept of web services is fluid. There are many...