Also a big fan of FMC for architecture diagrams - in bigger systems, being able to easily distinguish "action" vs "state" nodes has been useful in reasoning abo

Also a big fan of FMC for architecture diagrams - in bigger systems, being able to easily distinguish "action" vs "state" nodes has been useful in reasoning about behaviors. Pity it never took off, and there doesn't seem to be much tooling for it. For other uses - yeah, ERD and sequence diagrams are the workhorses.