While historical relation is used currently by most authors (+E3), two problems have been pointed out. First, the qualifier ``historical'' is too generic (-E5). Second, ``historical'' might be construed as referring only to the past, which could be misleading because a valid-time relation may also contain facts predicted to be valid in the future (-E8, -E9).
``Valid-time relation'' is straightforward and avoids these problems. Also, it is consistent with the name transaction-time relation (+E1).