Even after the death-of-XHTML2, syntax debate still dominates the day. Here is my contribution.
The XML story
In the beginning was SGML. There is a lot to be said about SGML so I won't. HTML was specified to be an application of SGML, but that never happened in practice. Among browsers Opera kept the pretence of supporting SGML for the longest time, causing us a lot of trouble because Opera behaved differently from every other browser. DocBook is another known SGML application, but in general SGML was no success.
About a decade ago a small group of people started a reformulation of the old SGML standard, First they did it outside of the W3C and later, when the success became apparent, within the W3C. The story of this simplified SGML, now known as XML, may be best told via the annotated XML, by Tim Bray, one of the principal authors. Essentially XML is angle brackets and a number of production rules on top of Unicode (for a fuller description see Comparison of SGML and XML). …