This function checks whether a document is being edited in tagged mode without a DTD. This function returns 1 (True) if the document identified by doc is an XML instance without a DTD declaration. This function also returns 1 if the document's declared DTD declaration cannot be found and the user selected to edit in tagged mode without a DTD. For all other documents, this function returns 0.

The doc argument specifies the identifier of the document to query. If omitted or 0, the current document is used.