/usr/share/xml/xhtml/schema/dtd/basic/ is in w3c-dtd-xhtml 1.2-4.
This file is owned by root:root, with mode 0o755.
..
/usr/share/xml/xhtml/schema/dtd/basic/catalog
/usr/share/xml/xhtml/schema/dtd/basic/catalog.xml
/usr/share/xml/xhtml/schema/dtd/basic/xhtml-arch-1.mod
/usr/share/xml/xhtml/schema/dtd/basic/xhtml-attribs-1.mod
/usr/share/xml/xhtml/schema/dtd/basic/xhtml-base-1.mod
/usr/share/xml/xhtml/schema/dtd/basic/xhtml-basic-form-1.mod
/usr/share/xml/xhtml/schema/dtd/basic/xhtml-basic-table-1.mod
/usr/share/xml/xhtml/schema/dtd/basic/xhtml-basic10-f.dtd
/usr/share/xml/xhtml/schema/dtd/basic/xhtml-basic10-model-1.mod
/usr/share/xml/xhtml/schema/dtd/basic/xhtml-basic10.dtd
/usr/share/xml/xhtml/schema/dtd/basic/xhtml-blkphras-1.mod
/usr/share/xml/xhtml/schema/dtd/basic/xhtml-blkstruct-1.mod
/usr/share/xml/xhtml/schema/dtd/basic/xhtml-charent-1.mod
/usr/share/xml/xhtml/schema/dtd/basic/xhtml-datatypes-1.mod
/usr/share/xml/xhtml/schema/dtd/basic/xhtml-framework-1.mod
/usr/share/xml/xhtml/schema/dtd/basic/xhtml-hypertext-1.mod
/usr/share/xml/xhtml/schema/dtd/basic/xhtml-image-1.mod
/usr/share/xml/xhtml/schema/dtd/basic/xhtml-inlphras-1.mod
/usr/share/xml/xhtml/schema/dtd/basic/xhtml-inlstruct-1.mod
/usr/share/xml/xhtml/schema/dtd/basic/xhtml-link-1.mod
/usr/share/xml/xhtml/schema/dtd/basic/xhtml-list-1.mod
/usr/share/xml/xhtml/schema/dtd/basic/xhtml-meta-1.mod
/usr/share/xml/xhtml/schema/dtd/basic/xhtml-notations-1.mod
/usr/share/xml/xhtml/schema/dtd/basic/xhtml-object-1.mod
/usr/share/xml/xhtml/schema/dtd/basic/xhtml-param-1.mod
/usr/share/xml/xhtml/schema/dtd/basic/xhtml-qname-1.mod
/usr/share/xml/xhtml/schema/dtd/basic/xhtml-struct-1.mod
/usr/share/xml/xhtml/schema/dtd/basic/xhtml-text-1.mod
/usr/share/xml/xhtml/schema/dtd/basic/xml1.dcl