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Stream: community: events

Topic: Topos Institute colloquium

view this post on Zulip John Baez (Jun 24 2023 at 20:52):

The Topos Institute has a colloquium every week, which (alas) is usually not announced here. But this week it's about work that a bunch of us have been doing on software for modeling epidemics, so I'm going to advertise it!

The talk is by my old grad school pal Nate Osgood. He's a computer scientist, he helped lead Canada's COVID modeling, and he is now spear-heading a project to develop software in AlgebraicJulia that uses ideas such as decorated cospans and operads to create disease models.

I am completely biased, since I'm involved in this - but I am really excited about how category theory, computer science and epidemiology are meeting in this project, and yielding practical tools for public health.

view this post on Zulip John Baez (Jun 24 2023 at 20:54):

His talk is Thursday June 29, 10:00-11:00 Pacific Time; to watch it either live or recorded go here.

Towards Compositional System Dynamics for Public Health

Abstract: For decades, System Dynamics (SD) modeling has served as a prominent, diagram-centric methodology used for public health modeling. Much of its strength arises from its versatile use of 3 types of diagrams, with each serving both to elevate transparency across the interdisciplinary teams responsible for most impactful models, and to reason about patterns of system behavior. Causal loop diagrams (CLDs) are used in semi-qualitative processes early in the modeling process and seek to support insight into feedback structure, behavioral modes, and leverage points. As modeling proceeds, system structure diagrams further distinguish stocks (accumulations) from flows and material from informational dependencies. Stock & flow diagrams build on that representation to characterize mathematical dependencies, quantify parameters and initial values for stocks, and have been particularly widely used in scenario simulation in public health and mathematical epidemiology.

While ubiquitous use of diagrams renders SD modeling markedly effective in supporting team science and shaping stakeholders’ mental models, existing tools suffer from a number of shortcomings. These include poor support for modularity, cumbersome and obscurant model stratification, and an inability to capture the relationships between the 3 diagram types. Within this talk, we describe initial progress towards creating a framework for compositional System Dynamics, including theory, API support via StockFlow.jl within AlgebraicJulia, and ModelCollab -- a real-time collaborative tool to support interdisciplinary teams in modularly building, composing and flexibly analyzing Stock & Flow diagrams.

Our approach separates syntax from semantics, and characterizes diagrams using copresheaves with a schema category. Diagram composition draws on the theory of structured cospans and undirected wiring diagrams, and employs pullbacks for model stratification. Model interpretation is achieved via functorial semantics, with ordinary differential equations being just one of several semantic domains supported. After describing the current state of implementation, we describe plans for future work, including enriching support for CLDs, and adding support for several computational statistics algorithms and additional types of structurally-informed model analyses. This is joint work with John Baez, Evan Patterson, Nicholas Meadows, Sophie Libkind, Alex Alegre and Eric Redekopp.

view this post on Zulip John Baez (Feb 13 2024 at 07:29):

I wish these colloquia were announced here! They are announced here:

Anyway, here's one:

view this post on Zulip Tim Hosgood (Feb 13 2024 at 21:43):

there's also a mailing list you can sign up to, and you can add the calendar to your computer calendar using researchseminars :-)

view this post on Zulip John Baez (Feb 13 2024 at 21:47):

Some smart people have gotten post titles from my Wordpress blog, posts on the category theory mailing list, etc. to be automatically copied here. Could someone do that for Topos colloquium announcements?

view this post on Zulip Tim Hosgood (Feb 14 2024 at 02:55):

quite possibly! but that someone is not me

view this post on Zulip John Baez (Feb 14 2024 at 05:35):

Yeah, there are people here who do such things.