Conceptually, a database consists of objects and relationships. Object Relationship Notation (ORN) __ is a simple notation that more precisely defines relationships by combining UML multiplicities with uniquely defined referential actions. This book shows how ORN can be used in UML class diagrams and database definition languages (DDLs) to better model and implement relationships and thus more productively develop database applications. For the database developer, it presents many examples of relationships modeled using ORN-extended class diagrams and shows how these relationships are easily mapped to an ORN-extended SQL or Object DDL. For the DBMS developer, it presents the specifications and algorithms needed to implement ORN in