Harald Ullrich Sandeep Purao Veda C. Storey An Ontology for Classifying the Semantics of Relationships in Database Design. 91-102 2000 conf/nldb/2000 NLDB http://link.springer.de/link/service/series/0558/bibs/1959/19590091.htm db/conf/nldb/nldb2000.html#UllrichPS00