Since Wikipedia is the biggest community edited knowledge platform, I would suggest to bind in articles in wikipedia
as classes in your graph.

Wikipedia itself has already many relationsships between "things" hidden in its links.

Maybe you can create a tool to systematically link these
articles together into hirarchies and general classes.


For the articels in Wikipedia itself, you could propose
a special type of "link" to that graph.
Something like

Dog:
[REL:SUBCLASS:Mammal]

with an explanation of its purpose.