The NFIRS specification provides this definition for Relational Edit Rule 4:
Relational Edit Rule 4 — If Transaction Type = 2 (delete) then duplicate should be found and only the data elements in the key should be provided. If Transaction Type = 3 (no monthly activity), then Alarm Date (YYYYMM), incident number (0), exposure number (0) are all that is required. Delete requires only the incident key fields (for matching). No Activity needs a timestamp and zero for incident number and exposure number.
