Atsushi Ohori. Semantics of Types for Database Objects. In Marc Gyssens, Jan Paredaens, Dirk Van Gucht, editors, ICDT 88, 2nd International Conference on Database Theory, Bruges, Belgium, August 31 - September 2, 1988, Proceedings. Volume 326 of Lecture Notes in Computer Science, pages 239-251, Springer, 1988. [doi]