Hi @BHAYT - Now I know! It seems that the dop files are over-written completely. In a very simple test I did the following:
- opened a folder with a dop in it
- made an edit (ClearView)
- Added IPTC data
- Moved away from the folder in the PhotoLibrary navigator
Step 3 created an .xmp file. But only at step 4 was a new dop created. Basically, then, it seems, the new dop will be created, as you say, once you start to edit a file - though it seems it may buffer the changes in memory and only write them when it looks like you have finished - moving away from the folder/closing the app (probably) - and maybe anyway after a certain time or number of changes.
In my case because I accidentally opened some images which I had edited in PL8 in PL7 I lost a lot of changes. For me the solution is simple; I removed PL7 to avoid any confusion.
Thanks for your input