First off I know asking "Why" for anything
standards related is silly.
But given that, could anyone give me a
rationale or history for restricting xml:id (or the ID type
from DTD) to be NCName which then has to start with
non-numeric ?
I seem to recall asking this once, and being told that the history
lay in the SGML rules for abbreviated syntax. Something like
allowing <e id="xyz"/> to be abbreviated as <e xyz>. Not
that this in itself would make a numeric identifier ambiguous, but
it would account for requiring an ID value to have the same syntax
as an attribute name.
I guess another justification is that it prevents any debate about
whether xml:id="01234" is a duplicate of xml:id="1234".
