I am *finally* making progress with @minOccurs and @maxOccurs after banging my forehead against the wall for ~9 hours (by throwing all my changes out and starting again), so I may well have time to look into this tomorrow. (There are several other things to be done, too.) Not all that facile with this stuff myself, but willing to give it a go.
I believe I've done the schema-related changes for release-blocking issue #536 (there are still bits of prose to change). Since this was adding a @source attribute in a new global class I did the various changes in a branch. I've not done anything about the testing which I'm sure the changes to classes (att.source and att.readFrom) will break. (But then again, I've never understood the testing and expected results as well as I should.) I'd appreciate someone looking at the changes and seeing if you see anything I've forgotten to do (other than prose updates in the chapters), and also to give me some advice on merging the branch in (or go ahead and do it if it looks good) and/or fixing the needed tests.
See most recent change at https://github.com/TEIC/TEI/tree/att.global.source namely https://github.com/TEIC/TEI/commit/69d00eb5b1f762eded61ad836a723c4ad0e4bc5d This changes 37 files with 96 additions and 119 deletions github tells me.