$$

$$

Scientists and engineers are often interested in representing the state of the world, . We might decide to encode this as the set of possible instances of a class,^{1} or as the set of terms of an algebraic data type,^{2} or as possible databases on a schema (i.e. -sets). We are also often interested in encoding the transition , a relationship between one state of the world and the *next* one. If we can communicate this relationship to a computer, then we can execute simulations to see how hypothetical states of the world evolve over time. The question we explore in this post is: **what is a good syntax for representing these kinds of functions?** Some virtues that we will care about:

This is a companion discussion topic for the original entry at https://blog.algebraicjulia.org/post/2023/07/graphical-schedule/index.html