"Wikidata is a free linked database that can be read and edited by both humans and machines. Wikidata acts as central storage for the structured data of its Wikimedia sister projects including Wikipedia, Wikivoyage, Wikisource, and others. Wikidata also provides support to many other sites and services beyond just Wikimedia projects! The content of Wikidata is available under a free license, exported using standard formats, and can be interlinked to other open data sets on the linked data web."

DCMI Metadata Terms

"This document is an up-to-date, authoritative specification of all metadata terms maintained by the Dublin Core Metadata Initiative. Included are the fifteen terms of the Dublin Core Metadata Element Set, which have also been published as IETF RFC 5013 [RFC5013], ANSI/NISO Standard Z39.85-2007 [NISOZ3985], and ISO Standard 15836:2009 [ISO15836]."