Molecular Objects, Abstract Data Types, and Data Models: A Framework

Abstract

Molecular objects occur frequently in CAD and engineering applications. At higher levels of abstraction they are treated as atomic unit,s of data; at lower levels they are defined in terms of a set of tuples possibly from different relations. System R’s complex objects are examples of molecular objects. In this paper, we present a framework for studying a generalized concept of molecular objects. We show that abstract data types unify this framework, which itself encompasses some recent data modeling contributions by researchers at IBM San Jose, Berkeley, Boeing, and Florida. A programming language/data structure paradigm is seen as a way of developing and testing the power of logical data models. A primary consequence of this paradigm is that future DBMSs must handle at least four distinct types of molecular objects: disjoint/non-disjoint and recursive/nonrecursive. No existing DBMS presently supports all these types.