On the Addition of Relations in an Abelian Category
P. J. Hilton, Y.-C. Wu · Canadian Journal of Mathematics · 1970
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.