Where is all the XML? Virtuoso creates XML from relational data. Get Ready to Liberate Your Data. It's that simple.
Virtuoso's SQL creates native XML data from relational data using SQLX extensions. Mapping schemas allow presenting joins of tables as XML entity hierarchies. These 'virtual documents' can be queried with XPATH which is translated to SQL to retrieve the relevant data and generate the XML on demand:
Virtuoso provides a broad range of functions for processing XML with extended SQL functions, including SQLX functions for creating XML, XSLT 1.2 for transformation, XPATH and XQuery, and DOM for manipulating XML trees.
This document is empty and basically useless. It is generated by a web service that can make some statements in HTML Microdata format. This time the service made zero such statements, sorry.