i am not talking about "full features and mathematical implications" but i would like to see a simpler model with a simple description. The existing model and implementation is already more complicated than justifiable (at least my impression; too many views and materialized maps and triggers). In general, we have to permission problem and the membership problem that has to deal with aggregations. With the current version in head, we have already a recursive query that is much better than the old permission stuff (with its maps, triggers, etc.). I wonder, whether making a few recursive queries to address the membership problem (with or without composition) would not offer a simpler solution.