/usr/share/dtds/jack_rack_1.1.dtd is in jack-rack 1.4.8~rc1-2ubuntu2.
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 | <!ELEMENT jackrack (channels, samplerate, plugin*)>
<!ELEMENT channels (#PCDATA)>
<!ELEMENT samplerate (#PCDATA)>
<!ELEMENT plugin (id, enabled, wet_dry_enabled, wet_dry_locked,
wet_dry_values, lockall?, controlrow*)>
<!ELEMENT id (#PCDATA)>
<!ELEMENT enabled (#PCDATA)>
<!ELEMENT wet_dry_enabled (#PCDATA)>
<!ELEMENT wet_dry_locked (#PCDATA)>
<!ELEMENT lockall (#PCDATA)>
<!ELEMENT wet_dry_values (value+)>
<!ELEMENT controlrow (lock?, value*)>
<!ELEMENT lock (#PCDATA)>
<!ELEMENT value (#PCDATA)>
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