title: the ccube constraint object-oriented database system. authors: alexander brodsky , pavel a. exarkhopoulo , victor e. segal , jia chen. venue: sigmod conference. year: 1999
title: schema and database evolution in the o2 object database system. authors: fabrizio ferrandina , thorsten meyer , roberto zicari , guy ferran , jo &#235; lle madec. venue: very large data bases. year: 1995