The specification has a problem with how the link types are defined.
The prose specification says:
rel
Proposed - Level 1. An attribute rel may give the relationship
(s) described by the hypertext link. The value is a
comma-separated list of relationship values. Values and their
semantics will be registered by the HTML registration
authority. The default relationship if none other is given is
void. rel should not be present unless href is present.
The problem is that the value can be a *comma*-separated list and the
DTD specifies the link type to be a NAME, and names can't contain commas:
<!ENTITY % linkType "NAME"
-- a list of these will be specified at a later date -->
<!ENTITY % URI "CDATA" -- see html-0.dtd -->
<!ENTITY % linkattributes-1
"REL %linkType #IMPLIED -- forward relationship type --
REV %linkType #IMPLIED -- reversed relationship type
to referent data: --
URN CDATA #IMPLIED -- universal resource number --
TITLE CDATA #IMPLIED -- advisory only --
METHODS NAMES #IMPLIED -- supported public methods of the object:
TEXTSEARCH, GET, HEAD, ... --
">
I think that either
1. change it to be a space-separated list and make
the link type NAMES, or
2. make the link type CDATA.
If there is few documents today that uses comma-separated lists, then
the first alternative is preferable.
-- Lennart Staflin <lenst@lysator.liu.se>