XQuery Recursion

declare function xf:subchannelfunc2($subChannelVal as element(ns1:subChannel)) as element(ns0:keySet) {

let $rs:= for $n in $subChannelVal/ns1:subChannel return xf:subchannelfunc2($n)
return

{ data($subChannelVal/ns1:channelName) }
{$rs}


};

http://www.sersc.org/journals/IJDTA/vol7_no3/16.pdf
google "xquery recursive function example"