The Fedora ontology is available online, but LDP clients have a hard time parsing it since it doesn't include a Content-Type header. It really MUST return a Content-Type header. I see that most other ontologies will redirect clients to a URL with a .rdf extension.
HTTP/1.1 200 OK
Date: Sun, 31 Jul 2016 13:09:56 GMT
Last-Modified: Mon, 02 May 2016 15:50:16 GMT