Furthermore, you can have several metadata tables that represent different types of graphs of the data tables, using all the relational features. For example,

Furthermore, you can have several metadata tables that represent different types of graphs of the data tables, using all the relational features. For example, one can implement role-based ACL on a tree structure in metadata tables, with one data table. Then sql can be used to get permissions, and even join on the data table, if that works for you.