The snapshot natural join can be generalized to incorporate valid time (the valid-time natural join), transaction time (the transaction-time natural join), or both (the bitemporal natural join). In each case, the schema resulting from the join is identical to that of the snapshot natural join appended with the timestamp(s) of the input relations.
``Temporal natural join'' directly generalizes the snapshot term ``natural join'' in that ``temporal'' is used as a modifier consistent with its previously proposed glossary definition (+E7). ``Natural time-join'' is less precise since it is unclear what is natural, i.e., is the join over ``natural time'' or is the time-join ``natural'' (-E7, -E9). ``Time-equijoin'' is also less precise since, in the snapshot model, the natural join includes a projection while the equijoin does not (-E7, -E9).