And indeed this is what's in the Recommended version of 2.0:
<![ %HTML.Recommended [
<!ENTITY % linkName "ID">
]]>
But case-folding is only part of it. An ID is an SGML NAME,
which given the sdecl must start with A-Za-z and may be followed
only by A-Za-z0-9.- . That is sufficiently restrictive that
given current usage, no intelligent implementor will attempt
to enforce it.
Might as well give up on this one and ditch the Recommended form
(not in 2.0, but when we get around to it).
Regards,
-- Terry Allen (terry@ora.com) O'Reilly & Associates, Inc. Editor, Digital Media Group 101 Morris St. Sebastopol, Calif., 95472A Davenport Group sponsor. For information on the Davenport Group see ftp://ftp.ora.com/pub/davenport/README.html or http://www.ora.com/davenport/README.html
Current HTML 2.0 spec: ftp://ds.internic.net/internet-drafts/draft-ietf-html-spec-04.txt