On the Resolution of Representational Diversity in Multidatabase Systems

Abstract

On the Resolution of Representational Diversity Joachim Hammer Department of Computer Science Stanford University Stanford, CA 94305 Dennis McLeoDepartment of Computer Science University of Southern California Los Angeles, CA 90089-0781 September 1995 1 Introduction A major problem that arises frequently when attempting to support information sharg among autonomous heterogeneous database systems is the occurrence of representational differences that exist among related data objects in different component systems. A collection of cooperating but heterogeneous, autonomous component database systems may be termed a multidatabase system (MDBS) [LMR90], or loosely-coupled federated database system [SL90]. Such cooperating systems attempt to support operations for partial and controlled sharing of data with minimal affect on existing applications. In this context, a key to supporting sharing involves folding of non-local data into the schema of an importing (local) component as gracefully as possible. Essential to achieving this is to support the resolution of semantic and representational (modeling) differences between the local and nonlocal perspectives. By resolving representational differences we mean two thin(1) determine as precisely as possible the relationships between sharable objects in different components, and (2) detect possible conflicts in their structural representations that pose problems when folding the non-local data into the local schema later on. In this chapter, we present an approach for resolving representational differences that preserves the autonomy of the participating databases. 2 Related Research Research in the area of collaboration among heterogeneous database systems (HDBSs) began only a decade ago [FS83, SBD + 81]. The term "heterogeneous databases" was originally used to distinguish work which included database model and conceptual schema heterogeneity from work in "distributed databases 1 " which addressed issues solely related to dist