<!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 >