RDF is listed on the linked page ("known XML languages"): https://xml.coverpages.org/xmlApplications.html https://xml.coverpages.org/xmlApplications.html SVG

RDF is listed on the linked page ("known XML languages"): https://xml.coverpages.org/xmlApplications.html https://xml.coverpages.org/xmlApplications.html SVG and MathML are also listed there, both of which seemed to be used a fair bit.