<!ELEMENT A ( host, iphostname ) > <!ELEMENT CNAME ( host, iphostname ) > <!ELEMENT MX ( host, preference, iphostname ) > <!ELEMENT NS ( iphostname ) > <!ELEMENT host ( #PCDATA ) > <!ELEMENT iphostname ( #PCDATA ) > <!ELEMENT preference ( #PCDATA ) > <!ELEMENT record ( A | CNAME | MX | NS )* > <!ELEMENT soa EMPTY > <!ATTLIST soa email CDATA #REQUIRED > <!ATTLIST soa expire NMTOKEN #REQUIRED > <!ATTLIST soa minimumttl NMTOKEN #REQUIRED > <!ATTLIST soa refresh NMTOKEN #REQUIRED > <!ATTLIST soa retry NMTOKEN #REQUIRED > <!ATTLIST soa serialdate NMTOKEN #REQUIRED > <!ATTLIST soa serialnum NMTOKEN #REQUIRED > <!ATTLIST soa ttl NMTOKEN #REQUIRED > <!ELEMENT zone ( soa, record+ ) > <!ATTLIST zone domain NMTOKEN #REQUIRED >