I was puzzled by the big ‘Thing’ blob there. I looked up in the latest foaf spec to see whether there is something new there, but then I realized that you meant owl:Thing… I think everything that is _not_ foaf should be very clearly shown. Which is the case, usually, because you add a namespace stuff for others, so this may be an exception. Maybe separating the foaf blobs from the others via a background colour would even be better.

The ‘Thing’ is, actually, a bit disturbing there, because it is not clear to the casual user that, say, an Agent is a Thing, ie, it could be used as an object for, say, primaryTopic. (I must admit I do not know how to capture that either, but it is always easier to critisize:-)

Adding those extras like sioc might be good but increases the clutter. I am not sure it helps here. If this was in SVG, I would say you should make that part clickable on/off, but that might be complicated for other formats… Maybe you should have two figures, one strictly on FOAF (well, the dc properties are useful, though) and the other with some ‘guests’.

I understand to leave out a bunch of properties to avoid clutter… But listing all the chat ID-s seems to be unnecessary, too. Having 1-2 makes it clear that it is where those would be used…

I hope this helps at least a little bit…