Property Covering: A Powerful Construct for Schema Derivations

Covering is a well known relationship in semantic and object oriented models that holds when a class is the union of a collection of subclasses Covering has been studied in the past only for entity classes In this paper we study covering for properties and we introduce a new relationship called property covering Property covering holds when a property is the union of a collection of subproperties Property covering allows to i partition a property into subproperties ii express property value re nement and iii express a particular form of negative informa tion We demonstrate that property covering is a powerful conceptual modeling mechanism and we use it to provide a set of inference rules for schema derivations