Standards

Desktop files: https://specifications.freedesktop.org/desktop-entry-spec/desktop-entry-spec-latest.html

Desktop files: https://standards.freedesktop.org/desktop-entry-spec/

XMP: https://developer.adobe.com/xmp/docs/XMPSpecifications

IPTC4XMP: http://xml.coverpages.org/IPTC-CoreSchema200503-ImplGuideLines3.pdf

Pango mark up: https://docs.gtk.org/Pango/pango_markup.html

Thumbnails: https://www.freedesktop.org/wiki/Specifications/thumbnails/