Definition:
An XML prolog consists of a declaration of the version of XML being used as well as the DTD that the document will validate against.
XML documents do not have to have the DTD to be well-formed, but it is required to be valid.
Also Known As: declaration
Examples:
<?xml version="1.0">
html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
