/usr/share/ontology/kde/kext.ontology is in kde-runtime-data 4:4.8.2-0ubuntu2.
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 | [Ontology]
Version=1.0
Name=KDE Extensions Ontology
Comment=The KDE Extensions Ontology contains extensions to the shared-desktop-ontologies that are not generic enough.
Namespace=http://nepomuk.kde.org/ontologies/2010/11/29/kext#
Path=/usr/share/ontology/kde/kext.trig
MimeType=application/x-trig
Type=Data
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