Contents of Definition

Definition

Informally, two tuples are snapshot equivalent if the snapshots of the tuples at all times are identical.

Let temporal relation schema R have n time dimensions, D_i, i = 1,…, n, and let τⁱ, i = 1,…, n be corresponding timeslice operators, e.g., the valid timeslice and transaction timeslice operators. Then, formally, tuples x and y are snapshot equivalent if

∀t₁∈D₁…∀t_n∈D_n(τⁿ_{t_n}(…(τ¹_t₁(x))…) = τⁿ_{t_n}(…(τ¹_t₁(y))…)) .

Similarly, two relations are snapshot equivalent if at every time their snapshots are equal. Snapshot equivalence is a binary relation that can be applied to tuples and to relations.