[basex-talk] xupdate question

Is there a particular reason why I can't do this (mixing let with copy/modify):

declare namespace ddi = "http://www.icpsr.umich.edu/DDI"; let $codeBook := collection()[1]/ddi:codeBook let $titlStmt := $codeBook/ddi:stdyDscr/ddi:citation/ddi:titlStmt copy $titlStmt1 := $titlStmt modify ( rename node $titlStmt1 as QName('http://www.icpsr.umich.edu/DDI%27,%27CopyOfTitlStmt') ) return $titlStmt1

but this works: declare namespace ddi = "http://www.icpsr.umich.edu/DDI"; copy $titlStmt1 := collection()[1]/ddi:codeBook/ddi:stdyDscr/ddi:citation/ddi:titlStmt modify ( rename node $titlStmt1 as QName('http://www.icpsr.umich.edu/DDI%27,%27CopyOfTitlStmt') ) return $titlStmt1

thanks *P