Source : Free On-Line Dictionary of Computing

Document Type Definition
     
         (DTD) The definition of a document type in
        {SGML} or {XML}, consisting of a set of {mark-up} tags and
        their interpretation.
     
        {Docbook DTD home (http://www.oasis-open.org/docbook/)}.
     
        {XML DTD Tutorial (http://www.xml101.com/dtd)}.
     
        (2001-04-30)