Hello,
I begin a work on an image comment (GPLv2/3) program with capability to read/write Iptc, Exif and Xmp comments (easy with python / pyexiv2 ;).

I wonder if there is already a public OSM "Xmp schema" to load, which will rely an "OSM xml schema fragment" to the "photography subject" (eg: a monument will be registered in a "Xmp.OSM.xmlfragment" container with all its tags (included geolocalisation, which is already given by Xmp GPS details) )?

In case not, would please some studies that, then post back the schema URL?
Python pyexiv2 has capability to load xmp shemas by URI.

Thanks!
TSFH