subcategory,supercategory,kind
Set,Pfn,total restriction
Top,AdmRep,total restriction
FinOrd,FinSet,skeleton
Mat_k,FinVect_k,skeleton
Pos,Pros,skeleton
Inj,Set,essentially wide
Pfn,Rel,essentially wide
Surj,Set,essentially wide
Bij,Set,core
Hilb₀,Hilb,core
Perm,FinSet,core
SymmRel,Rel,core