In the tag historian, when you rename a tag it loses reference to the previously named history. It retires the tag, but if you query with the new name you cant see any of the historical data with the old name. If the tag history entry table for tag paths included a self-referencing retired_id column that showed the previous tagid, then you would be able to query tag history even previous to tag name changes. This would be great in scenarios where you get things running in a dev environment and start collecting data, and then down the road you need to rename the tag to match a newer scheme.