/usr/share/xml/docbook/schema/dtd/4.4/ is in docbook-xml 4.5-7ubuntu1.
This file is owned by root:root, with mode 0o755.
..
/usr/share/xml/docbook/schema/dtd/4.4/calstblx.dtd
/usr/share/xml/docbook/schema/dtd/4.4/catalog
/usr/share/xml/docbook/schema/dtd/4.4/catalog.xml
/usr/share/xml/docbook/schema/dtd/4.4/dbcentx.mod
/usr/share/xml/docbook/schema/dtd/4.4/dbgenent.mod
/usr/share/xml/docbook/schema/dtd/4.4/dbhierx.mod
/usr/share/xml/docbook/schema/dtd/4.4/dbnotnx.mod
/usr/share/xml/docbook/schema/dtd/4.4/dbpoolx.mod
/usr/share/xml/docbook/schema/dtd/4.4/docbook.cat
/usr/share/xml/docbook/schema/dtd/4.4/docbookx.dtd
/usr/share/xml/docbook/schema/dtd/4.4/ent
/usr/share/xml/docbook/schema/dtd/4.4/htmltblx.mod
/usr/share/xml/docbook/schema/dtd/4.4/soextblx.dtd