I'm not reacting well to the use of the term "keyword". This usually indicates informal topical access rather than structured access like skos concepts or classification schemes. I think that a term like "subject" or "topic" would be better understood as including the formal schemes.
note that the keyword implementation suggested in Appendix 1 allows for both informal 'tags' and concepts-- labels with URIs.
per comments from Karen Coyle
note that the keyword implementation suggested in Appendix 1 allows for both informal 'tags' and concepts-- labels with URIs.