Great list of languages that don't fit the conventional families. I've been curious about some of them, like Petri nets and term rewriting, and will enjoy exploring the others.

Found a working link to the paper about propagators.

The Art of the Propagator, Alexey Radul and Gerald Jay Sussman. https://groups.csail.mit.edu/mac/users/gjs/6.945/readings/ar... (PDF)