Definition:Agreement/Mappings

Definition
Let:
 * $(1): \quad f_1: S_1 \to T_1$ be a mapping from $S_1$ to $T_1$


 * $(2): \quad f_2: S_2 \to T_2$ be a mapping from $S_2$ to $T_2$


 * $(3): \quad X \subseteq S_1 \cap S_2$

If:
 * $\forall s \in X: f_1 \left ({s}\right) = f_2 \left ({s}\right)$

then the mappings $f_1$ and $f_2$ are said to agree on or be in agreement on $X$.