Like most (but not all) other XML-related specifications from the W3C, this specification was written in XML, using tools that included GNU Emacs and Notepad. The HTML version is produced by the application of a bunch of custom Java code; with any luck, this will be the last time. For example, the XSL Working Drafts have been produced using a much better stylesheet-driven mechanism.
Back-link to specCopyright © 1998, Tim Bray. All rights reserved.