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  1. Changes made only to the Universal property of the 2-category of spans section. The citations by Urs lead to another citation which, in turn, leads to another citation. With a little effort, I tracked down the a full copy of said universal property, I’ve replicated it here, added the citation used, although I left the previous citations there for convenience; a more experienced editor can remove those if they would like.

    I would like to note that the author whose work I have referenced, Hermida, also notes: “[this universal property] is folklore although we know no references for it.”

    Please make any corrections needed and clean up the language here; this is a fairly direct copy of what is written, but I imagine somebody with more knowledge of all the language used here can rewrite this universal property stuff in a cleaner way.



    diff, v57, current

  2. Correcting Tex errors from previous edit


    diff, v57, current

    • CommentRowNumber3.
    • CommentAuthorUrs
    • CommentTimeOct 20th 2021


    I have touched the formatting a little (here).

    Where the factorization of functors is mentioned, I have added “such functors” and “FF as above” to make sure it’s unambiguous.

    The citation by Hermida I moved up to before Pronk et al. and I added the DOI link.

    Might it make sense to keep some reference from the text to Dawson, Paré & Pronk? (This is a genuine question, as I would have to remind myself on what it is they are saying.)

    diff, v58, current

  3. added definition of spans and correspondences in dependent type theory (those two objects are not the same in dependent type theory)


    diff, v62, current

  4. added definition of span in set theory


    diff, v64, current

    • CommentRowNumber6.
    • CommentAuthorvarkor
    • CommentTimeDec 29th 2023

    Added an early reference for the terminology.

    diff, v66, current

    • CommentRowNumber7.
    • CommentAuthorvarkor
    • CommentTimeMay 14th 2024

    Added two more references of Walker that give universal properties of Span.

    diff, v67, current