Stock and flow diagrams are already an important tool in epidemiology, but
category theory lets us go further and treat these diagrams as mathematical
entities in their own right. In this chapter we use communicable disease models
created with our software, StockFlow.jl, to explain the benefits of the
categorical approach. We first explain the category of stock-flow diagrams and
note the clear separation between the syntax of these diagrams and their
semantics, demonstrating three examples of semantics already implemented in the
software: ODEs, causal loop diagrams, and system structure diagrams. We then
turn to two methods for building large stock-flow diagrams from smaller ones in
a modular fashion: composition and stratification. Finally, we introduce the
open-source ModelCollab software for diagram-based collaborative modeling. The
graphical user interface of this web-based software lets modelers take
advantage of the ideas discussed here without any knowledge of their
categorical foundations.

该研究论文使用 StockFlow.jl 创建传染病模型解释了范畴论方法的优势，并介绍了使用组合和分层这两种模块化方法构建大规模进出流图的方法，以及介绍了基于图形用户界面的网络软件 ModelCollab。