in old xhtmls we can declare smthing like this:
<!DOCTYPE html PUBLIC A B [ <!ENTITY nbsp " "> ] >
where for example
A := "-//W3C//DTD XHTML+RDFa 1.0//EN"
B := "http://www.w3.org/MarkUp/DTD/xhtml-rdfa-1.dtd"
How to do this properly in xhtml 5 ?
example(s) appreciated, TIA.