and removing the “parallel associativity” or “commutativity” which says that composing $h\in C(y_1,\dots,y_n;z)$ with two morphisms $f\in C(x_1,\dots,x_n ; y_i)$ and $g\in C(w_1,\dots,w_p; y_j)$ can be done in either order.

A morphism $f$ is central if for any $g$ and $h$ as above, the two methods of composition commute: $(h \circ f) \circ g = (h \circ g) \circ f$. So a premulticategory is a multicategory precisely if all morphisms are central.

Relation to premonoidal categories

A premulticategory that has all tensor products and units, in a usual multicategorical sense, is equivalent to a premonoidal category.

References

Sam Staton and Paul Blain Levy, Universal properties of impure programming languages. POPL ‘13: Proceedings of the 40th annual ACM SIGPLAN-SIGACT symposium on Principles of programming languages, 2013, doi

Last revised on November 7, 2023 at 17:46:03.
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