While historical relation is used currently by most authors (+E3), two problems have been pointed out. First, the qualifyer ``historical'' is too generic (-E5). Second, ``historical,'' being a reference to the past, is misleading because a valid-time relation may also contain facts valid in the future (-E8, -E9).
``Valid-time relation'' is straight forward and avoids these problems. Also, it is consistent with ``transaction time relation,'' to be discussed next (+E1).