The current draft does not specify how to compare rel values and Property type
URIs. This is a problem since these are not obvious.

Relation-types comparison is defined in Web Linking [1] :

Registered relation type names MUST conform to the reg-relation-type rule, and MUST be compared character-by-character in a case- insensitive fashion.

When extension relation types are compared, they MUST be compared as URIs in a case-insensitive fashion, character-by-character. Because of this, all-lowercase URIs SHOULD be used for extension relations.

I think we should incorporate this language because it might not be obvious to
developers who are not likely to study the Web Linking spec. Since we have a
dependency on Web Linking, we will have to wait for it to get published as an
RFC (at least approved by the IESG), and if this changes, we will follow.

BTW, I have an open issue with the above text because I think "compared as URIs"
is poorly defined (is http://example.com/rel the same as
http://example.com:80/rel?).

As for Property type URIs, I think they must follow the same rules as the
extension relation types.

EHL

[1] http://tools.ietf.org/html/draft-nottingham-http-link-header