Mauricio J. V. Silva C. Robert Carlson Modeling Active Object-Oriented Database Application Using Multi-Level Diagrams. 306-311 1996 conf/compsac/1996 COMPSAC http://doi.ieeecomputersociety.org/10.1109/CMPSAC.1996.544181 db/conf/compsac/compsac1996.html#SilvaC96