Easiest way to get your head around the SPARQL thing is to try it.
Download, and run the two .sh files, one for a server, one for a client. You'll need gmail and LiveJournal accounts. Also it'll look in /Users/danbri/foafns/foaf.rdf for some sample data to serve, but you can probably recompile and change that. It's just Jena...
For added realism, do it from different machines :)
