12. The system of claim 11 , wherein said database system is a relational database system, wherein said plurality of data items are stored in the form of a plurality of tables characterized by a set of primary keys and a set of foreign keys, wherein said schema indicates for each table a corresponding primary key and a corresponding subset of foreign keys, wherein each primary entity is a table containing a primary key and a corresponding secondary entity is a table having an associated foreign key tied to said primary key.
11. The system of claim 10 , wherein said identifying comprises examining data representing a schema defining said plurality of entity types in said database system, wherein said schema further defines attributes of each entity type and specifies the primary entity and the secondary entity for each of said plurality of relationships.