Lojban doesn't really classify relations at all:
the gismu list is a large and disorderly bag whose merit is that it
blankets semantic space,
has this really been demonstrated?
How does one demonstrate that? (Or, for starters, measure semantic
space?)
I would have thought one thing Lojban does very well is classifying
relations. "Semantic space" is just a (sometimes) convenient metaphor.
There is no real space out there to be carved up into concepts.
Well, in a sense there is. If we only had thirty-five gismu (the lowest
minimum I've heard claimed as necessary) then we would need them all to
encompass a great deal of stuff.