Bicategory of Spans

The bicategory of spans of a category $\mathcal{C}$ with Binary Pullbacks is the Bicategory $\mathrm{Span}(\mathcal{C})$ where

• Objects are objects of $\mathcal{C}$
• 1-cells are Spans $A\leftarrow R\to B$.
• 2-cells are Morphisms of Spans.

References

• https://ncatlab.org/nlab/show/span#UniversalPropertyOfTheBicategoryOfSpans