Storing and Querying XML Data in Object-Relational DBMSs

Abstract

As the popularity of eXtensible Markup Language (XML) continues to increase at an astonishing pace, data management systems for storing and querying large repositories of XML data are urgently needed. In this paper, we investigate an Object-Relational DBMS (ORDBMS) for storing and querying XML data. We present an algorithm, called XORator, for mapping XML documents to tables in an ORDBMS. An important part of this mapping is assigning a fragment of an XML document to a new XML data type. We demonstrate that using the XORator algorithm, an ORDBMS is usually more efficient than a Relational DBMS (RDBMS). Based on an actual implementation in DB2 V.7.2, we compare the performance of the XORator algorithm with a well-known algorithm for mapping XML data to an RDBMS. Our experiments show that the XORator algorithm requires less storage space, has much faster loading times, and in most cases can evaluate queries faster. The primary reason for this performance improvement is that the XORator algorithm results in a database that is smaller in size, and queries that usually have fewer number of joins.

This work was supported in part by the National Science Foundation under NSF grant IIS-0208852, by an IBM CAS Fellowship, and by gift donations from IBM and NCR.