John F. Roddick Aaron Ceglar Denise de Vries Somluck La-Ongsri Postponing Schema Definition: Low Instance-to-Entity Ratio ( LItER ) Modelling. 206-216 2006 Active Conceptual Modeling of Learning http://dx.doi.org/10.1007/978-3-540-77503-4_16 conf/er/2006acml db/conf/er/acml2006.html#RoddickCVL06