The main motivation for using XQuery is for querying XML databases. Most commercial relational database
systems now offer a way to keep and select information in XML but some XML native databases have been developed.
eXist-db  is an open source database management system that
stores XML data according to the XML data model and features efficient index-based XQuery processing.
java -cp /path/to/the/SAXON.jar net.sf.saxon.Query -s WineCatalog.xml \ -q WineCatalog.xq color=white > whites.html