sieve

Last updated January 27, 2022

Definition

Let $C$ be a category, $c\in\text{Obj}(C)$. Let $C/c$ be the over category.

• A sieve $S$ is
  • a collection of arrows in $C$ with target $c$ (i.e. $S\subset\text{Obj}(C/c)$)
  • closed under precomposition