The HTML spec has *both* REL and REV. Both attributes can be lists
of relationships. The occurence of a relationship in the REV
(reverse) list indicates a relationship in th ereverse direction.
Otherwise, you have to have a convention for indicating logically
reverse relationships (eg is-child; has-child) or some
out of band system for knowing that
A is-parent-of B
implies and is implied b by
B is-child-of A
Is there any document where REV is present withouit REL?
Tim