Can’t I use UDTs in a Tag Driving Provider?
No, unfortunately they cannot. It certainly has been requested a number of times, but I don’t think it will likely happen, at least in the current form of external tags.
What we will likely do is tweak the format just a bit to have a more “hybrid” approach, where the udt/tags are defined internally, but their values are published through the db. This would achieve the main result of sharing tags through the database, but would be a little different than how it currently works.