Haifeng Shen Siyuan Liu Steven Xia Chengzheng Sun Distributed Constraints Maintenance in Collaborative UML Modeling Environments. 367-370 2008 ASE http://dx.doi.org/10.1109/ASE.2008.50 conf/kbse/2008 db/conf/kbse/ase2008.html#ShenLXS08