@neauoire :) yes, it is related to petri nets: graph rewriting on a (labelled) discrete graph is equivalent to a petri net. edges make things more fun, so Kappa is more general. we are working on a yet more general variant called CSet rewriting mainly for use in epidemiology (https://johncarlosbaez.wordpress.com/2024/05/13/agent-based-models-part-9/). we do not yet have a very good surface syntax for it, though, so Modal and Thue (less so Maude, it is quite complicated) are good inspiration.