The publishing profiles for Author-it Magellan content use the Saxon parser to generate the output. Saxon-HE "provides implementations of XSLT 3.0, XQuery 3.1, and XPath 3.1 at the basic level of conformance defined by W3C." In other words, Saxon parses XML content and transforms it using XSLT stylesheets when exporting Author-it content.
For instructions on how to install Saxon for Author-it, see Install Saxon in the Author-it Knowledge Center.