Abstract
A number of authors have observed that regularity of a category A is not necessary for the existence of a "calculus of relations" in A, with an associative composition of relations giving a 2-category Rel A; it suffices that the finitely-complete A have a proper factorization system (ε,M) whose class ε is stable by pullbacks, the classical regular-category case being that where M consists of all the monomorphisms. We show that this generalization is in a sense illusory: if B is the category of "maps" in Rel A, then B is a regular category, and Rel A is isomorphic to the classical Rel B.
The author acknowledges with gratitude the support of the Australian Research Council.
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© 1991 Springer-Verlag
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Kelly, G.M. (1991). A note on relations relative to a factorization system. In: Carboni, A., Pedicchio, M.C., Rosolini, G. (eds) Category Theory. Lecture Notes in Mathematics, vol 1488. Springer, Berlin, Heidelberg. https://doi.org/10.1007/BFb0084224
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DOI: https://doi.org/10.1007/BFb0084224
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