Attempting an SGML-PARSE action specifying an element that is not declared in the current SGML DTD.
          #6107   Run-time catchable error
          Attempting an SGML-PARSE action specifying an element that is not declared in the current SGML DTD.
Explanation
This error occurs when an attempt is made in the OmniMark program
to do an SGML parse using INSTANCE and a WITH DOCUMENT-ELEMENT that specifies an element not defined in the
specified DTD (e.g., in an translation-type before ).