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math.CT2021
Quotients of span categories that are allegories and the representation of regular categories
S. Naser Hosseini, Amir R. Shir Ali Nasab, Walter Tholen +1
We consider the ordinary category Span(C) of (isomorphism classes of) spans of morphisms in a category C with finite limits as needed, composed horizontally via pullback, and give…
math.CT2019
Fraction, Restriction and Range Categories from Non-Monic Classes of Morphisms
S. N. Hosseini, A. R. Shir Ali Nasab, W. Tholen
For a composition-closed and pullback-stable class S of morphisms in a category C containing all isomorphisms, we form the category Span(C,S) of S-spans (s,f) in C with first "leg"…