Link Relationship for Moving Down a Hierarchy

HTML5 has "up" as a link relationship, but nothing for the opposite
direction. I'd been using rev="up" for this, but since @rev has been
removed from HTML5 I'd like to specify an inverse relationship to use.
Would the obvious name, "down", be most sensible, or something like
"sub", or some other proposal? Has this been discussed before?

Should a "down" link relationship conform to the same repetition
semantics as "up"?

My use case is for archived pages whose contents I can't modify
without of course making them non archived content. I want to link to
ancient pages and mark them up as being sub-pages of the page that
discusses them.

-- 
Sean B. Palmer, http://inamidst.com/sbp/