/usr/include/sdformat-6.0/sdf/ is in libsdformat6-dev 6.0.0+dfsg-4.
This file is owned by root:root, with mode 0o755.
..
/usr/include/sdformat-6.0/sdf/Assert.hh
/usr/include/sdformat-6.0/sdf/Console.hh
/usr/include/sdformat-6.0/sdf/Element.hh
/usr/include/sdformat-6.0/sdf/Error.hh
/usr/include/sdformat-6.0/sdf/Exception.hh
/usr/include/sdformat-6.0/sdf/Filesystem.hh
/usr/include/sdformat-6.0/sdf/Param.hh
/usr/include/sdformat-6.0/sdf/Root.hh
/usr/include/sdformat-6.0/sdf/SDFImpl.hh
/usr/include/sdformat-6.0/sdf/Types.hh
/usr/include/sdformat-6.0/sdf/World.hh
/usr/include/sdformat-6.0/sdf/parser.hh
/usr/include/sdformat-6.0/sdf/parser_urdf.hh
/usr/include/sdformat-6.0/sdf/sdf.hh
/usr/include/sdformat-6.0/sdf/sdf_config.h
/usr/include/sdformat-6.0/sdf/system_util.hh