Right. That's the easy part. But how do you know if you should use "IPTC:Rating", "Rating", "xmp:Rating", or "photoshop:Urgency"? All of those are listed in the various tables in the .cpp files, but only "IPTC:Rating" actually works. If you add an attribute called "Rating" in your example above it just disappears into the void, with no error messages. It would be nice to have the process for choosing the manufactured variable name described in a comment, perhaps in the .cpp file next to the tables with all the id strings? Not a big deal. Just mentioning it because I had to try each variant before I figured out which one worked and wanted to save others the same trouble.