[html5] general question about the semantic web

[onno de jong]

If this question is too general, please point me to more specific links. I'm wrapping my head around the notion of a semantic web, or making the web friendly for machines to interpret meaning so as to facilitate data such that humans can better consume the content, what Tim Berners-Lee now calls linked data, as I understand it.  

To what extent did these semantic requirements drive the original development of XHTML 2? and what role should these semantic indicators play in the way content ought to be marked up in HTML5?