Directed Multigraph

A directed multigraph consists of a H-Set of vertices V 𝑉 V , an H-Set of vertices E 𝐸 E , and a pair of maps src , tgt : E → V : src tgt → 𝐸 𝑉 \mathrm{src},\mathrm{tgt}:E\to V . More abstractly, a directed multigraph graph is a Presheaf over the Walking Parallel Pair.