Published online by Cambridge University Press: 20 November 2018
In [1] the category of relations in an abelian category
was studied. A relation from A to B appeared as an equivalence class of pairs of
-morphisms (ϕ, ψ),
Moreover, this equivalence class may be written as the composite , where
is canonically embedded in
and
is the image of Γ in the canonical involution on
. Every equivalence class has an essentially unique minimal representative (ϕ0,ψ0), characterized by the property that
where
and if and only if the square
is exact.