Query Object Framework - XML backend module

 QOF is a framework to allow the execution of SQL-type
 queries using collections of in-memory objects as 'tables'.
 .
 This module provides the default XML backend for libqof2
 using a generic XML format called QSF. Any QOF object can
 be written out or loaded from QSF XML. Data can be
 converted to other text-based formats using XSL.