Amir Sapir Ehud Gudes Dynamic Relationships and Their Propagation and Concurrency Semantics in Object-Oriented Databases. 94-111 http://link.springer.de/link/service/series/0558/bibs/1649/16490094.htm 1999 conf/ngits/1999 NGITS db/conf/ngits/ngits99.html#SapirG99