Quora answer: Why are there so many projects to build The One Ontology to Rule Them All?

It is like programming languages only not as bad, why are there so many programming languages being developed now? Because there are a myriad ideas on how to do it and they are fighting out a survival of the fittest sort of game. What is really happening is that a lot of domain specific ontologies are being created. One ontology to rule them all is a pipe dream. The implicit knowledge in the world is just too complex. As far as I know only Cyc has the idea of trying to explicitly cover everything. I recommend Sowa’s approach Guided Tour of Ontology