/usr/lib/libreoffice/share/dtd/officedocument/ is in libreoffice-common 1:5.1.2-0ubuntu1.
This file is owned by root:root, with mode 0o755.
..
/usr/lib/libreoffice/share/dtd/officedocument/1_0/
/usr/lib/libreoffice/share/dtd/officedocument/1_0/Manifest.dtd
/usr/lib/libreoffice/share/dtd/officedocument/1_0/accelerator.dtd
/usr/lib/libreoffice/share/dtd/officedocument/1_0/chart.mod
/usr/lib/libreoffice/share/dtd/officedocument/1_0/datastyl.mod
/usr/lib/libreoffice/share/dtd/officedocument/1_0/defs.mod
/usr/lib/libreoffice/share/dtd/officedocument/1_0/dialog.dtd
/usr/lib/libreoffice/share/dtd/officedocument/1_0/drawing.mod
/usr/lib/libreoffice/share/dtd/officedocument/1_0/dtypes.mod
/usr/lib/libreoffice/share/dtd/officedocument/1_0/event.dtd
/usr/lib/libreoffice/share/dtd/officedocument/1_0/form.mod
/usr/lib/libreoffice/share/dtd/officedocument/1_0/groupuinames.dtd
/usr/lib/libreoffice/share/dtd/officedocument/1_0/image.dtd
/usr/lib/libreoffice/share/dtd/officedocument/1_0/libraries.dtd
/usr/lib/libreoffice/share/dtd/officedocument/1_0/library.dtd
/usr/lib/libreoffice/share/dtd/officedocument/1_0/menubar.dtd
/usr/lib/libreoffice/share/dtd/officedocument/1_0/meta.mod
/usr/lib/libreoffice/share/dtd/officedocument/1_0/module.dtd
/usr/lib/libreoffice/share/dtd/officedocument/1_0/nmspace.mod
/usr/lib/libreoffice/share/dtd/officedocument/1_0/office.dtd
/usr/lib/libreoffice/share/dtd/officedocument/1_0/office.mod
/usr/lib/libreoffice/share/dtd/officedocument/1_0/script.mod
/usr/lib/libreoffice/share/dtd/officedocument/1_0/settings.mod
/usr/lib/libreoffice/share/dtd/officedocument/1_0/statusbar.dtd
/usr/lib/libreoffice/share/dtd/officedocument/1_0/style.mod
/usr/lib/libreoffice/share/dtd/officedocument/1_0/table.mod
/usr/lib/libreoffice/share/dtd/officedocument/1_0/text.mod
/usr/lib/libreoffice/share/dtd/officedocument/1_0/toolbar.dtd