The W3C Recommendation Process
The W3C is the body that issues standards for the World Wide Web. As a matter of fact, the W3C has no formal power as a standards body. In fact, SGML is not a W3C Recommendation: It is an ISO standard.
That is why the standard documents that are formally published by the W3C are called Recommendations. They are adopted as standards by the Web community through a consensus. That is, manufacturers, authors, and users agree to abide by the recommendations of the W3C, even though none are formally required to do so.
Note
There are numerous examples of deviations from W3C standards. The best examples are browser extensions to HTML, such as the dreaded <BLINK> tag. Both Microsoft and Netscape have strayed from W3C recommendations in the past to extend the functionality of their browsers. The cost, however, is that Web authors using these extended features limited their audiences to users of certain browsers, defeating the purpose of HTML.
The XML Recommendation's origins began with the SGML Editorial Review Board. This board, working in conjunction with the SGML Working Group, was working toward adapting SGML to uses with the World Wide Web.
In 1996, the XML Working Group was formed to develop XML into a formal recommendation. Building on the work of people such as James Clark, Jon Bosak, and Dan Connolly, the final version was authored by Tim Bray, Jean Paoli, and C. M. Sperberg-McQueen. It became an official W3C Recommendation on February 10, 1998, and the final version can be found at the official XML 1.0 Recommendation Web site: http://www.w3.org/TR/1998/REC-xml-19980210.