The W3C Systeam’s blog has a hilarious item W3C’s Excessive DTD Traffic. Apparently, generic XML systems are trying to download the DTD using the DOCTYPE declaration system identifier (i.e. what it is for) on XHTML files, or downloading the schemas from the namespace URI (i.e. not what it is for) for documents with XHTML fragments. And it is a lot of bogus traffic. W3C does not want to cop having to serve dumb XHTML requests for DTDs and schemas. A different DOCTYPE and a lazy loading parser policy would help. But I think all the ISO/MathML special character public entity sets should be built into XML.