I think instead you should check out 
   <URL:http://www.eit.com/projects/s-http/> - I honestly feel that this 
   kind of information should be dealt with external to the HTML document 
   itself, because a solution that works like that will also work for any 
   kind of datatype.
There is a good intro to SGML principles at
   ftp://www.ucc.ie/pub/sgml/p2sg.ps
///Peter