You're reading the public-facing archive of the Category Theory Zulip server.
To join the server you need an invite. Anybody can get an invite by contacting Matteo Capucci at name dot surname at gmail dot com.
For all things related to this archive refer to the same person.
Very broad question but, does there exist a category theoretic approach to machine learning algorithms on multigraphs?
I'm not aware of much existing work—simple graphs are more common—but the main results of Graph Neural Networks are Dynamic Programmers are valid for multigraphs. (they even apply to some hypergraphs, those where edges have one receiver but multiple senders)
Multigraphs are much more natural, categorically, speaking, than simple graphs. A multigraph is exactly a span from a set to itself, and spans are a fundamental concept.
There's also the paper of mine Learning Functors using Gradient Descent that works on multigraphs.
This is from the categorical side. I'd expect there to be many papers in the machine learning community doing various things with multigrpahs.