Regular Languages and Model Theory 3: Constraint Systems and NFAs
In this video, I introduce the notion of a triangular constraint system, and a nondeterministic finite automaton.
You can play with triangular constraint systems here: https://trkern.github.io/constraintsy...
Nondeterministic finite automata can alternately be thought of as deterministic finite automata but with randomness involved, where we say an NFA accepts if there is at least one timeline (at least one set of results of the randomness) in which it accepts. This perspective is perhaps better for thinking about multiple timelines in terms of our experience with NFAs than it is for thinking about NFAs in terms of our experience with multiple timelines.
If you have questions or something didn't make sense to you, please let me know in the comments below.