,
Fabio Zanasi
Creative Commons Attribution 4.0 International license
We introduce string diagrams for graded symmetric monoidal categories. Our approach includes a definition of graded monoidal theory and the corresponding freely generated syntactic category. Also, we show how an axiomatic presentation for the graded theory may be modularly obtained from one for the grading theory and one for the base category. The Para construction on monoidal actegories is a motivating example for our framework. As a case study, we show how to axiomatise a variant of the graded category ImP, recently introduced by Liell-Cock and Staton to model imprecise probability [Liell-Cock and Staton, 2025]. This culminates in a representation, as string diagrams with grading wires, of programs with primitives for nondeterministic and probabilistic choices and conditioning.
@InProceedings{sarkis_et_al:LIPIcs.CALCO.2025.5,
author = {Sarkis, Ralph and Zanasi, Fabio},
title = {{String Diagrams for Graded Monoidal Theories, with an Application to Imprecise Probability}},
booktitle = {11th Conference on Algebra and Coalgebra in Computer Science (CALCO 2025)},
pages = {5:1--5:23},
series = {Leibniz International Proceedings in Informatics (LIPIcs)},
ISBN = {978-3-95977-383-6},
ISSN = {1868-8969},
year = {2025},
volume = {342},
editor = {C\^{i}rstea, Corina and Knapp, Alexander},
publisher = {Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
address = {Dagstuhl, Germany},
URL = {https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.CALCO.2025.5},
URN = {urn:nbn:de:0030-drops-235641},
doi = {10.4230/LIPIcs.CALCO.2025.5},
annote = {Keywords: string diagrams, graded categories, probability, nondeterminism}
}