nice! that's something i stumbled over when re-architecting a 2-sided marketplace (in rails) for one of my startups. the data model they describe is roughly what i ended up with, but it took some iterating to get there. the key understanding was that the relation table in a many-to-many relationship is not just a technical detail but encodes important information about real world systems, especially the human kind. as engineers, we get often get stuck on the entities being the important bits, but more often, the relations are where all the action is.