Is Invisible XML missing from RelaxNG for 3.1?

Hi all,

Am I missing it or are both p:ixml and p:invisible-xml missing from the 
schema(s) for XProc 3.1? 
(https://spec.xproc.org/master/head/xproc/xproc31.rng)  If they really 
aren't there, is this deliberate?  I was expecting the latter, if not 
also the former.

Kind regards,

Sheila