As we mentioned earlier, all documents are made up of a prolog and a body.
The document prolog contains the XML Declaration and the document body contains
the actual marked up document. Recall from previous sections that
we had developed a CONTACTS XML document that looked something like the following:
<!--Beginning of prolog-->
<?xml version = "1.0" encoding="UTF-8" standalone = "yes"?>
<!--End of prolog-->
<!--Beginning of body-->
<!--End of body-->
What we did not say earlier was that the prolog also holds the DTD.