Object Relationship Notation (ORN) for Database Applications

except for brief excerpts in connection with reviews or scholarly analysis. Use in connection with any form of information storage and retrieval, electronic adaptation, computer software, or by similar or dissimilar methodology now known or hereafter developed is forbidden. The use in this publication of trade names, trademarks, service marks, and similar terms, even if they are not identified as such, is not to be taken as an expression of opinion as to whether or not they are subject to proprietary rights. Preface Conceptually, information that is relevant to a database application consists of objects and relationships. Since the advent of object-orientation in the 1980s, much emphasis has been placed on objects and, in my opinion, too little on the relationships that exist among them. Many books have been written about objects. This book is about relationships. The emphasis on objects in software systems analysis, design, and implementation has improved the productivity of developing and maintaining software systems. I believe that placing more emphasis on relationships can have a similar effect, especially for database systems. This book is founded on that belief. Motivation The motivation for this book is the same as the motivation driving the research and its results that are the subject of this book. This motivation originated in 1990 when I attended a class on Ontos, an early object database management system (ODBMS). Despite much support in the system for the storing of objects, i.e., object persistence, I saw little support for relationships, specifically the types of relationships that bind different objects together. A classic example of this type of relationship is the one-to-many relationship that binds each object representing a department to the objects representing the employees who work for the department. The support for such relationships improved little in later ODBMSs and in a subsequent ODBMS standard. I viewed the support for relationships in ODBMSs to be slightly less than that provided by relational database management systems (RDBMSs). And this latter support has, I believe, been dismal, especially when one considers the age and pervasiveness of RDBMSs and the fact that for decades relational databases have been developed based on the Entity-Relationship (ER) model. This belief has provided even more motivation for the contents of this book. When the relationships defined in ER models are implemented in relational databases, much of their meaning—expressed by their one-to-one, one-to-many, many-to-many, and cardinal-ity notations—is lost or very difficult …