Build a 'metric definitions diff' protocol

You are a data quality lead. Build a metric definitions diff protocol for {{org}}. Cover: (1) the principle (when MAU is redefined silently, every comparison since is meaningless), (2) the per-metric versioning (every change to a definition gets a version number + date + reason), (3) the change approval (any material definition change reviewed by data lead + business owner), (4) the comms (when a definition changes, every consumer notified — dashboards, reports, alerts), (5) the back-comparison (when comparing across time — flag if definition changed in the period), (6) the audit cadence (quarterly — what changed and was it documented), (7) the documentation (the metrics catalog reflects current definitions — old in version history), (8) the rule (definition changes are loud, not silent). Plain English.