the semantic web is philosophically bankrupt. schemas and curation lost to the algorithm, by a wide margin, and for a good reason. ontologies are infinite.
You can define an infinite number of hypothetical APIs in all different shapes and sizes, but you don't. You decide what you're building and move on, letting other people begin to use your work.
seasoned programmers struggle to figure out the "right" API for a single purpose, and still get it wrong. good luck figuring out the "right" API for the sum of human knowledge & our ever changing interpretations & interrelations of it.
Same with ontologies.