Using relational database functionalities have these bennefits:
well known - everybody knows how it works.
secure - databases implements security and audit functionalities
according to security standard.
hirarchical - representation of user and roles which his permisions.
insert/update - permisions are controled at table level and
individual columns.
delete/select - permisions are controled only a table level.
Last point is a drawback from the point of view of DBPrism CMS because we need
to control the access rigths to the page metadata stored in a same table, so
users must see some rows and musn't see anothers.
