I occasionally get obsessed with ontologies, thesauri, hierarchical classifications of general --> specific knowledge. Ok, it's a lifelong obsession since I was a kid, fascinated by the Dewey Decimal System... I mean, how
do you classify knowledge in hierarchies? [trees of interdependent, cross referenced structures that are called webs instead of trees can also be thought of as multidimensional trees with some fascinating properties, such as growing back towards the trunk and intersecting with it... such is where analogies start to take on alien form].
Anyway, my DDC curiosity reasserted itself again, leading me to find some fascinating resources. The Bartoc . org [Basel Register of Thesauri, Ontologies & Classifications] lists 2384 significant ones, which led me to the PLOS thesaurus at:http://www.vocabularyserver.com/plos/index.php
Being PLOS, it's related to Science of course, but what a marvelous job they did of presenting a hierarchical view.
I find "how humans classify reality" to be fascinating.... mostly due to its absurdity and yet, we continue because.