Christoph Koch Zsolt Kovacs Jean-Marie Le Goff Richard McClatchey Paolo Petta Tony Solomonides Explicit Modeling of the Semantics of Large Multi-layered Object-Oriented Databases. 52-65 http://link.springer.de/link/service/series/0558/bibs/1920/19200052.htm 2000 ER db/conf/er/er2000.html#KochKGMPS00