/usr/share/doc/mkvtoolnix/examples/matroskatags.dtd is in mkvtoolnix 19.0.0-1.
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 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 | <!ELEMENT Tags (Tag*)>
<!ELEMENT Tag (
Targets,
Simple*)>
<!ELEMENT Targets (
TrackUID*,
ChapterUID*,
AttachmentUID*,
EditionUID*,
TargetType?,
TargetTypeValue?)>
<!ELEMENT TrackUID (#PCDATA)>
<!ELEMENT ChapterUID (#PCDATA)>
<!ELEMENT AttachmentUID (#PCDATA)>
<!ELEMENT EditionUID (#PCDATA)>
<!ELEMENT TargetType (#PCDATA)>
<!ELEMENT TargetTypeValue (#PCDATA)>
<!ELEMENT Simple (
Name,
String?,
Binary?,
TagLanguage?,
DefaultLanguage?,
Simple*)>
<!ELEMENT Name (#PCDATA)>
<!ELEMENT String (#PCDATA)>
<!ELEMENT Binary (#PCDATA)>
<!ELEMENT TagLanguage (#PCDATA)>
<!ELEMENT DefaultLanguage (#PCDATA)>
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