However, HTML files may have this line in the <head> element:
<link href='http://blueobelisk.sourceforge.net/people/egonw/foaf.xrdf'
rel='meta' title='FOAF' type='application/rdf+xml'/>
This could be the trigger for a Strigi plugin, to download this file and provide that as substream for the HTML file. I am aware for security issues at immediately pop up, but that is something we can surely deal with.
Using this approach the whole semantic desktop takes shape. Say, I am searching what I have on my desktop on some topic, then, additionally, Strigi will make me aware that I recently read the blog from someone who showed interest in that topic too. Moreover, it will even allow Strigi to tell me which projects on SourceForge are related to this topic.
Far fetched? No, it's really just around the corner. If interested, you may find the source code in KDE SVN under trunk/playground/utils/strigi-foaf. The Konqueror history hack is not implemented yet, as I need to know first what efforts are ongoing in that respect.