FWIW, only a subset of the Dublin Core has been selected for use inside epubs. That set varies from epub "2" to epub "3.0" to what is the latest epub "3.1" spec.
You really have to read the detailed epub specs to find out the exact subset, attributes allowed, extensions, etc.
For example: Here is the latest epub "3.1" spec for metadata:
http://www.idpf.org/epub/31/spec/epu...c-pkg-metadata
Here is the epub 3.0 spec:
http://www.idpf.org/epub/301/spec/ep...-metadata-elem
And the same for the epub2 spec:
http://www.idpf.org/epub/20/spec/OPF...htm#Section2.2
Whereas the full DC spec is quite extensive and can be much more involved.