See http://www.markus-lanthaler.com/hydra/spec/latest/core/ I first though the apiDocument referenced with the link header could be an extended ontology document (http://fusepool.eu/ontologies/ecs# / https://github.com/fusepool/fusepool-ecs/blob/master/ontologies/src/main/resources/eu/fusepool/ecs/ontologies/ecs.ttl) but now I see the apiDocument is tied to a particular entry point.
See http://www.markus-lanthaler.com/hydra/spec/latest/core/
I first though the apiDocument referenced with the link header could be an extended ontology document (http://fusepool.eu/ontologies/ecs# / https://github.com/fusepool/fusepool-ecs/blob/master/ontologies/src/main/resources/eu/fusepool/ecs/ontologies/ecs.ttl) but now I see the apiDocument is tied to a particular entry point.