XQueryX is not supposed to be a "new and improved" query language. It's just an alternate representation of the XQuery language. See the very first paragraph

XQueryX is not supposed to be a "new and improved" query language. It's just an alternate representation of the XQuery language. See the very first paragraph of the introduction: The [XML Query 1.0 Requirements] states that "The XML Query Language MAY have more than one syntax binding. One query language syntax MUST be convenient for humans to read and write. One query language syntax MUST be expressed in XML in a way that reflects the underlying structure of the query." XQueryX is an XML representation of an XQuery. It was created by mapping the productions of the XQuery grammar into XML productions. The result is not particularly convenient for humans to read and write, but it is easy for programs to parse, and because XQueryX is represented in XML, standard XML tools can be used to create, interpret, or modify queries.