ScalingStacks

Remark 4.13. For $N=2$ the foam $2$-category $\boldsymbol{\mathrm{Foam}}_{2}$ can be replaced by the $2$-category (or canopolis) of Bar-Natan’s dotted cobordisms [3, Section 11.2]; see [6]. The morphism categories of the latter can also be described as categories of finitely-generated graded projective modules for Khovanov’s arc rings [18].