From:   http://www.imppwg.org/local/draft-mazzoldi-prim-impp-01.txt
Presence and Instant Messaging Protocol (PRIM)

15.7.   Presence Document DTD

      <!ENTITY % URI "CDATA">
      <!ENTITY % statuses "open|closed">
      <!-- The entity "details" is defined as CDATA for
           extensibility. But, the only distiuguished value
           "deferred" has a meaning at present. -->
      <!ENTITY % details "CDATA">

      <!-- the presence tag is the top-level tag for presence. -->
      <!ELEMENT presence (presentity?,contact)>
      <!ATTLIST presence identifier %URI; #REQUIRED>
      <!ATTLIST presence date CDATA #REQUIRED>

      <!ELEMENT presentity (display-name, note?, other-markup?)>

      <!ELEMENT display-name (#PCDATA)>

      <!ELEMENT note (#PCDATA)>

      <!ELEMENT other-markup (#PCDATA)>

      <!-- the contact tag is for each tuple. -->
      <!ELEMENT contact (display-name, status,
                         preference?, note?,
                         other-markup?)>

      <!ATTLIST contact address %URI; #IMPLIED>

      <!ELEMENT status EMPTY>
      <!ATTLIST status value (%statuses;) #REQUIRED>
      <!ATTLIST status detail %details; #IMPLIED>
      <!ELEMENT preference EMPTY>
      <!ATTLIST preference value CDATA #REQUIRED>