<!ELEMENT logs (trail|req_machine|req_date)+>
<!ELEMENT req_machine (#PCDATA)>
<!ELEMENT req_date (#PCDATA)>
<!ELEMENT trail (log)+>
<!ELEMENT log (log|sig)>
<!ELEMENT sig (#PCDATA)>
<!ATTLIST log
   sev     CDATA #REQUIRED
   tstamp  CDATA #REQUIRED
   msg     CDATA #REQUIRED
>