fhttp:get-query-args() returns a node-set consisting of
one 'requestParameters' element, containing one child
element for each item in the HTTP request parameters,
a.k.a. the query arguments (typically HTML form data).
The HTTP server will have already decoded the parameters
and made them available to the XSLT processor; this
function merely provides access to that data as a
node-set. The parameter name becomes the element name,
and the value is the element's content. If there are
multiple parameters with the same name, they'll manifest
as separate elements.