Span

$Span$ is the bicategory, or double category, whose

- objects are sets
- (horizontal) morphisms are spans
- 2-cells are morphisms of spans
- (in the double category case) vertical morphisms are functions.

More generally, we have $Span(C)$ consists of spans in $C$ for any category $C$ with pullbacks.

$Span$ is a sort of classifying object for arbitrary functors; see *displayed category*.

There is an (infinity,n)-category of correspondences.

Last revised on May 12, 2017 at 05:58:56. See the history of this page for a list of all contributions to it.