set-doctype(doc_name, public_id, system_id, internal_subset?)

Add, change or remove <!DOCTYPE> in the document being modified by the XED script.

When parameter internal_subset is not specified or is the empty string, the <!DOCTYPE> will have no internal subset.

When parameters doc_name, public_id and system_id are all passed the empty string, the <!DOCTYPE> is removed from the document.

Examples:

set-doctype("html", "-//W3C//DTD XHTML 1.0 Strict//EN", "xhtml1-strict.dtd");

set-doctype("html", "-//W3C//DTD XHTML 1.0 Strict//EN", "xhtml1-strict.dtd", 
            '<!ENTITY xxe "XMLmind XML Editor">');

set-doctype("", "", "");