Ernst-Erich Doberkat Eugenio G. Omodeo Algebraic Semantics of ER-Models in the Context of the Calculus of Relations. II: Dynamic View. 50-65 2001 conf/RelMiCS/2001 RelMiCS http://link.springer.de/link/service/series/0558/bibs/2561/25610050.htm db/conf/RelMiCS/RelMiCS2001.html#DoberkatO01