/usr/include/KF5/Syndication/syndication/rdf/ is in libkf5syndication-dev 17.12.3-0ubuntu1.
This file is owned by root:root, with mode 0o755.
..
/usr/include/KF5/Syndication/syndication/rdf/contentvocab.h
/usr/include/KF5/Syndication/syndication/rdf/document.h
/usr/include/KF5/Syndication/syndication/rdf/dublincore.h
/usr/include/KF5/Syndication/syndication/rdf/dublincorevocab.h
/usr/include/KF5/Syndication/syndication/rdf/image.h
/usr/include/KF5/Syndication/syndication/rdf/item.h
/usr/include/KF5/Syndication/syndication/rdf/literal.h
/usr/include/KF5/Syndication/syndication/rdf/model.h
/usr/include/KF5/Syndication/syndication/rdf/modelmaker.h
/usr/include/KF5/Syndication/syndication/rdf/node.h
/usr/include/KF5/Syndication/syndication/rdf/nodevisitor.h
/usr/include/KF5/Syndication/syndication/rdf/parser.h
/usr/include/KF5/Syndication/syndication/rdf/property.h
/usr/include/KF5/Syndication/syndication/rdf/rdf.h
/usr/include/KF5/Syndication/syndication/rdf/rdfvocab.h
/usr/include/KF5/Syndication/syndication/rdf/resource.h
/usr/include/KF5/Syndication/syndication/rdf/resourcewrapper.h
/usr/include/KF5/Syndication/syndication/rdf/rssvocab.h
/usr/include/KF5/Syndication/syndication/rdf/sequence.h
/usr/include/KF5/Syndication/syndication/rdf/statement.h
/usr/include/KF5/Syndication/syndication/rdf/syndicationinfo.h
/usr/include/KF5/Syndication/syndication/rdf/syndicationvocab.h
/usr/include/KF5/Syndication/syndication/rdf/textinput.h