# Serial Relation is not Null

Jump to navigation Jump to search

## Theorem

Let $S$ be a set such that $S \ne \O$.

Let $\RR$ be a serial relation on $S$.

Then $\RR$ is not a null relation.

## Proof

As $S$ is non-empty set:

$\exists x: x \in S$

As $\RR$ be a serial relation on $S$:

$\exists y \in S: \tuple {x, y} \in \RR$

That is:

$\RR \ne \O$

Hence the result by definition of null relation.

$\blacksquare$