Reda Alhajj Faruk Polat Closure Maintenance in An Object-Oriented Query Model. 72-79 CIKM1994/P072.pdf 1994 conf/cikm/94 CIKM db/conf/cikm/cikm94.html#AlhajjP94 db/conf/cikm/AlhajjP94.html http://doi.acm.org/10.1145/191246.191262