Done: ACTION A-641-14

Done and checked in.  I used the term “associated expression” rather than “fallback expression”.

Jonathan

ACTION A-641-14 on Jonathan and Michael Dyck to agree revised wording to
resolve the potential ambiguity in the resolution of action A-636-08 as
described in
https://lists.w3.org/Archives/Public/public-xsl-query/2016Apr/0020.html.