Updating a schema

If I add an optional element to a sequence within a schema, which means that all of the existing data will still be valid, would I still have to undefine the existing schema and then save the updated schema into Tamino, or is Tamino intelligent enogh to see that the change will not invalidate existing data?

Currently I seem to have to undefine any existing schema and save the new one, no matter how trivial the change. This is cumbersome and dangerous, since all of the data has to be saved first. surely the option to save the data could be added into the undefine process?

Yes, I tried it and it works at any position of the sequence, if the element is optional.