This document gives recommendations to manage data reconciliations from Exif, IPTC-IIM and XMP from different points of view, including the one of a "Changer" (XnViewMP for example), as well to read metadatas or to write them.
It would be nice if XnViewMP was MWG Guidelines compliant for the 'XMP only' mode of the Metadata Editor (which mode should be the default one).
http://www.metadataworkinggroup.org/pdf ... idance.pdf
Metadata Working Group Guidelines
Moderators: XnTriq, helmut, xnview