Theorem. let C be a category then the section preorder of Hom is the J preorder of C.
Proof. let m: a \to b and n: c \to d be morphisms in C. Then for m \subseteq n in the section preorder of Hom it must be the case that there exists an ordered pair: (i : c \to a, o : b \to d) \in C^{op} \times C o \circ m \circ i = n This is precisely the definition of m \subseteq_J n. It follows that the J preorder of C is the section preorder of Hom. \square
This constructs the overall morphic preordering of a category C from its hom copresheaf Hom : C^{op} \times C \to Sets. There are two other morphic preorders associated with a category C: the L and R preorders, both of which are suborders of J.

Lemma. let F : C \to Sets be a functor and let S \subseteq C be a wide subcategory then the section preorder of F_S is a subpreorder of the section preorder of F.
Proof. let (t_1,x_1) \subseteq (t_2, x_2) in the section preorder of F_S then \exists m : t_1 \to t_2 \in S such that F_S(m)(x_1) = x_2. But since S \subseteq C we have that m : t_1 \to t_2 in C such that F(m)(x_1) = x_2. So a \subseteq_{F_S} b implies that a \subseteq_{F} b, which means that the section preorder of F_S is a subpreorder of that of F. \square
We can use this lemma to construct the specialized L and R preordering on the morphism set of a category as subpreorders of the J preorder produced by the Hom bicopresheaf.
Theorem. let C be a category and Hom : C^{op} \times C \to Sets its hom bicopresheaf. Then the output action preorder L is the the section preorder of the restriction of Hom to the wide subcategory with only output actions and R is the section preorder of the resrtiction of Hom to the wide subcategory containing only input actions.
Proof. if m: a \to b \subseteq_L n: a \to c this means that there exists o : b \to c with o \circ m = n which is the same as saying there is (1_a, o) in the wide subcategory of C^{op} \times C with only output actions. Similarily for the right preorder \subseteq_R, so the L and R preorders are formed by the section preorders of restrictions of the hom bicopresheaf. \square
This produces an interpretation of the morphic preorders of a category C that is much more suitable for our purposes. We can now define the morphic preordering of C to simply be the object preordering of the category of elements of the hom functor. We have now two types of preorders on a category, both of which are object preorders of their respective categories:
- The preorder on Ob(C) is the object preorder of C.
- The preorder on Arrows(C) is the object preorder of the category of elements of the hom functor.
References:
Hom functor
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