/usr/share/xml/dbus-1/introspect.dtd is in libdbus-1-dev 1.12.2-1ubuntu1.
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 | <!-- DTD for D-Bus Introspection data -->
<!-- (C) 2005-02-02 David A. Wheeler; released under the D-Bus licenses,
GNU GPL version 2 (or greater) and AFL 1.1 (or greater) -->
<!-- see D-Bus specification for documentation -->
<!ELEMENT node (node|interface)*>
<!ATTLIST node name CDATA #IMPLIED>
<!ELEMENT interface (method|signal|property|annotation)*>
<!ATTLIST interface name CDATA #REQUIRED>
<!ELEMENT method (arg|annotation)*>
<!ATTLIST method name CDATA #REQUIRED>
<!ELEMENT signal (arg|annotation)*>
<!ATTLIST signal name CDATA #REQUIRED>
<!ELEMENT arg (annotation)*>
<!ATTLIST arg name CDATA #IMPLIED>
<!ATTLIST arg type CDATA #REQUIRED>
<!-- Method arguments SHOULD include "direction",
while signal and error arguments SHOULD not (since there's no point).
The DTD format can't express that subtlety. -->
<!ATTLIST arg direction (in|out) "in">
<!-- AKA "attribute" -->
<!ELEMENT property (annotation)*>
<!ATTLIST property name CDATA #REQUIRED>
<!ATTLIST property type CDATA #REQUIRED>
<!ATTLIST property access (read|write|readwrite) #REQUIRED>
<!ELEMENT annotation EMPTY> <!-- Generic metadata -->
<!ATTLIST annotation name CDATA #REQUIRED>
<!ATTLIST annotation value CDATA #REQUIRED>
|