/usr/share/tudu/tudu.dtd is in tudu 0.8.1-1.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 | <!ELEMENT todo (title?, date?, priority?, category*, text?, scheduled?,todo*)>
<!ATTLIST todo
done ( yes | no ) "no"
collapse ( yes | no ) "no">
<!ELEMENT title (#PCDATA)>
<!ELEMENT deadline (day, month, year)>
<!ELEMENT day (#PCDATA)>
<!ELEMENT month (#PCDATA)>
<!ELEMENT year (#PCDATA)>
<!ELEMENT priority (#PCDATA)>
<!ELEMENT category (#PCDATA)>
<!ELEMENT text (#PCDATA)>
<!ELEMENT scheduled (day, month, year,position?)>
<!ELEMENT position (#PCDATA)>
|