/usr/share/X11/xkb/rules/xkb.dtd is in xkb-data 2.23.1-1ubuntu1.
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 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 | <?xml version="1.0" encoding="UTF-8"?>
<!--
Description: XKB configuration file DTD
Author: Sergey V. Udaltsov
-->
<!ELEMENT xkbConfigRegistry (modelList,layoutList,optionList)>
<!ATTLIST xkbConfigRegistry
version CDATA "1.1">
<!ELEMENT modelList (model*)>
<!ELEMENT model (configItem)>
<!ELEMENT layoutList (layout*)>
<!ELEMENT layout (configItem,variantList?)>
<!ELEMENT optionList (group*)>
<!ELEMENT variantList (variant*)>
<!ELEMENT variant (configItem)>
<!ELEMENT group (configItem,option*)>
<!ATTLIST group
allowMultipleSelection (true|false) "false">
<!ELEMENT option (configItem)>
<!ELEMENT configItem (name,shortDescription*,description*,vendor?,countryList?,languageList?,hwList?)>
<!ATTLIST configItem
popularity (standard|exotic) "standard">
<!ELEMENT name (#PCDATA)>
<!ELEMENT shortDescription (#PCDATA)>
<!ELEMENT description (#PCDATA)>
<!ELEMENT vendor (#PCDATA)>
<!ELEMENT countryList (iso3166Id+)>
<!ELEMENT iso3166Id (#PCDATA)>
<!ELEMENT languageList (iso639Id+)>
<!ELEMENT iso639Id (#PCDATA)>
<!ELEMENT hwList (hwId+)>
<!ELEMENT hwId (#PCDATA)>
|