Hi Pascal,<div><br></div><div>it comes down to a syntax error - there&#39;s a &#39;return&#39; statement missing</div><div>before the &#39;copy&#39;. It should work like this:</div><div><br></div><div><div><i>declare namespace ddi = &quot;<a href="http://www.icpsr.umich.edu/DDI">http://www.icpsr.umich.edu/DDI</a>&quot;;</i></div>

<div><i>let $codeBook := collection()[1]/ddi:codeBook</i></div><div><i>let $titlStmt := $codeBook/ddi:stdyDscr/ddi:citation/ddi:titlStmt</i></div><div><i><b>return</b> copy $titlStmt1 := $titlStmt</i></div><div><i>modify (</i></div>

<div><i>   rename node $titlStmt1 as</i></div><div><i>QName(&#39;<a href="http://www.icpsr.umich.edu/DDI">http://www.icpsr.umich.edu/DDI</a>&#39;,&#39;CopyOfTitlStmt&#39;)</i></div><div><i>)</i></div><div><i>return $titlStmt1</i></div>

</div><div><i><br></i></div><div>I always check queries in the Query Editor of BaseX if I come across</div><div>issues like this. Just as a hint ...</div><div><br></div><div><br></div><div>Cheers,</div><div>Lukas</div>