Hi John: Much of the XML DB's out there simply serialize the structure. This may work to a degree, but it ignores the power in RDBMS, and makes the XML -> RDBMS mapping (and inverse mapping) slow. Could you provide more details on what your system does? My interest is in part because I have built an XML -> RDBMS mapper which doesn't serialize the data structure, nor ties one to a particular database. Joe -- Joseph Landman, Ph.D Scalable Informatics LLC email: landman at scalableinformatics.com web: http://scalableinformatics.com phone: +1 734 612 4615