<!ELEMENT stuMessages (stuMessage*)>
<!ATTLIST stuMessages
  timeStamp CDATA #REQUIRED
  messageID CDATA #REQUIRED
>
<!ELEMENT stuMessage (esn, unixTime, gps, payload)>
<!ELEMENT esn (#PCDATA)>
<!ELEMENT unixTime (#PCDATA)>
<!ELEMENT gps (#PCDATA)>
<!ELEMENT payload (#PCDATA)>
<!ATTLIST payload
  length CDATA #REQUIRED
  source (pc | unix) #REQUIRED
  encoding CDATA #REQUIRED
>