Overriding default behavior of XHTML compatibility guidelines

Hi All,

I've recently come across a situation where I'd like to create an XSLT 
1.0 stylesheet that outputs XHTML that conforms to the XHTML 
compatibility guidelines for HTML browser parsers (Appendix C of the 
XHTML 1 specification). Usually, this happens automatically when the XML 
serializer within libxml detects an XHTML doctype. Unfortunately, in my 
case, I'm using the XHTML + RDFa doctype, which isn't in the hard coded 
list of doctypes which trigger Appendix C conformant output. Looking at 
the libxml code, the serialization API does provide an option to 
override this default behaviour regardless of the doctype (see 
xmlSaveOption enum). Unfortunately, it seems libxslt doesn't make use of 
this functionaility at all and simply uses the serialization methods 
which just sniff the doctype against the hard coded list of known XHTML 
doctypes.

My knowledge of this subject is very limited and my conclusions from my 
investigations could well be flawed, so I'd appreciate any input from 
those who know much more than I on this subject.

To be more precise, my <xsl:output> element looks like this...

<xsl:output method="xml"
     doctype-public="-//W3C//DTD XHTML+RDFa 1.0//EN"
     doctype-system="http://www.w3.org/MarkUp/DTD/xhtml-rdfa-1.dtd"
     omit-xml-declaration="yes"
     encoding="UTF-8"
     indent="yes"/>

But looking at xmlsave.c in libxml2, the hard coded list of doctypes 
which trigger Appendix C conformant output looks like this:

#define XHTML_STRICT_PUBLIC_ID BAD_CAST \
    "-//W3C//DTD XHTML 1.0 Strict//EN"
#define XHTML_STRICT_SYSTEM_ID BAD_CAST \
    "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd"
#define XHTML_FRAME_PUBLIC_ID BAD_CAST \
    "-//W3C//DTD XHTML 1.0 Frameset//EN"
#define XHTML_FRAME_SYSTEM_ID BAD_CAST \
    "http://www.w3.org/TR/xhtml1/DTD/xhtml1-frameset.dtd"
#define XHTML_TRANS_PUBLIC_ID BAD_CAST \
    "-//W3C//DTD XHTML 1.0 Transitional//EN"
#define XHTML_TRANS_SYSTEM_ID BAD_CAST \
    "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"

Any help greatly appreciated.