/usr/share/xml/ is in xhtml-relaxng 20151127+dfsg-1.
This file is owned by root:root, with mode 0o755.
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/usr/share/xml/xhtml-relaxng/
/usr/share/xml/xhtml-relaxng/exclude/
/usr/share/xml/xhtml-relaxng/exclude/basic-table.rnc
/usr/share/xml/xhtml-relaxng/exclude/basic-table.rng
/usr/share/xml/xhtml-relaxng/exclude/basic.rnc
/usr/share/xml/xhtml-relaxng/exclude/basic.rng
/usr/share/xml/xhtml-relaxng/exclude/form.rnc
/usr/share/xml/xhtml-relaxng/exclude/form.rng
/usr/share/xml/xhtml-relaxng/index.html
/usr/share/xml/xhtml-relaxng/modules/
/usr/share/xml/xhtml-relaxng/modules/applet.rng
/usr/share/xml/xhtml-relaxng/modules/attribs.rng
/usr/share/xml/xhtml-relaxng/modules/base.rng
/usr/share/xml/xhtml-relaxng/modules/basic-form.rng
/usr/share/xml/xhtml-relaxng/modules/basic-table.rng
/usr/share/xml/xhtml-relaxng/modules/bdo.rng
/usr/share/xml/xhtml-relaxng/modules/csismap.rng
/usr/share/xml/xhtml-relaxng/modules/datatypes.rng
/usr/share/xml/xhtml-relaxng/modules/edit.rng
/usr/share/xml/xhtml-relaxng/modules/events.rng
/usr/share/xml/xhtml-relaxng/modules/form.rng
/usr/share/xml/xhtml-relaxng/modules/frames.rng
/usr/share/xml/xhtml-relaxng/modules/hypertext.rng
/usr/share/xml/xhtml-relaxng/modules/iframe.rng
/usr/share/xml/xhtml-relaxng/modules/image.rng
/usr/share/xml/xhtml-relaxng/modules/inlstyle.rng
/usr/share/xml/xhtml-relaxng/modules/legacy.rng
/usr/share/xml/xhtml-relaxng/modules/link.rng
/usr/share/xml/xhtml-relaxng/modules/list.rng
/usr/share/xml/xhtml-relaxng/modules/meta.rng
/usr/share/xml/xhtml-relaxng/modules/nameident.rng
/usr/share/xml/xhtml-relaxng/modules/object.rng
/usr/share/xml/xhtml-relaxng/modules/param.rng
/usr/share/xml/xhtml-relaxng/modules/pres.rng
/usr/share/xml/xhtml-relaxng/modules/ruby.rng
/usr/share/xml/xhtml-relaxng/modules/script.rng
/usr/share/xml/xhtml-relaxng/modules/ssismap.rng
/usr/share/xml/xhtml-relaxng/modules/struct.rng
/usr/share/xml/xhtml-relaxng/modules/style.rng
/usr/share/xml/xhtml-relaxng/modules/table.rng
/usr/share/xml/xhtml-relaxng/modules/target.rng
/usr/share/xml/xhtml-relaxng/modules/text.rng
/usr/share/xml/xhtml-relaxng/xhtml-basic.rng
/usr/share/xml/xhtml-relaxng/xhtml-strict.rng
/usr/share/xml/xhtml-relaxng/xhtml.rng