XQuery node-name() function, how is it work? -

i want add additional pairs each pair.
have kind of code:

<data> <pair>     <key>keyname1</key>     <value>something1</value> </pair> <pair>     <key>keyname2</key>     <value>something2</value> </pair> <pair>     <key>keyname3</key>     <value>             <listofpairs>                 <pair>                     <key>keyname4</key>                     <value>something6</value>                 </pair>             </listofpairs>     </value> </pair> <pair>     <key>keyname5</key>     <value>something9</value> </pair> </data> 

and need insert other pairs after each pair no matter in level, prefix: "copy" different value:

<data> <pair>     <key>keyname1</key>     <value>something1</value> </pair> <pair>     <key>copy_keyname1</key>     <value>another1</value> </pair> <pair>     <key>keyname2</key>     <value>something2</value> </pair> <pair>     <key>copy_keyname2</key>     <value>another2</value> </pair> <pair>     <key>keynamedwithlists</key>     <value>         <listofpairs>             <pair>                 <key>keyname4</key>                 <value>something6</value>             </pair>             <pair>                 <key>copy_keyname4</key>                 <value>another6</value>             </pair>         </listofpairs>     </value> </pair> <pair>     <key>keyname5</key>     <value>something9</value> </pair> <pair>     <key>copy_keyname5</key>     <value>another9</value> </pair> </data> 

for kind of result get, need use function: node-name()? how work? how should use it? ore maybe should use function?

as @jens-erat mentioned, don't need node-name(), instead presumably want this:

<data> { $pair in /data/pair return     ($pair,     <pair>         <key>{concat("copy_", $pair/key)}</key>         <value>some other value</value>     </pair>) }</data> 

update - mentioned in comment, copy outer-most pairs, if want copy pairs no matter depth, need use recursive descent transform input.

i found writing in xquery particular use case quite challenge, although solution rather elegant think :-) interested if else can think of better implementation?

xquery version "1.0";  declare function local:copy-pair($pair element(pair), $copying) element(pair)+ {     (         if(not($copying))then             $pair         else(),         <pair>             <key>{concat("copy_", $pair/key)}</key>                 { local:recursive-descent($pair/key/following-sibling::node(), true()) }             </pair>     ) };  declare function local:recursive-descent($nodes, $copying) {     $node in $nodes     return         (         typeswitch($node)             case element(pair) return                 local:copy-pair($node, $copying)              case element() return                 element {node-name($node)} {                     local:recursive-descent($node/node(), $copying)                 }              case text() return                 if($copying , $node/parent::value , empty($node/parent::value/element()))then                     text { concat("some new value. old value = ", $node) }                 else                     $node              default return                 (                     $node,                     local:recursive-descent($node/node(), false())                 )         ) };  local:recursive-descent(/data, false()) 

the recursive-descent function left-to-right recursive-descent through node tree. element named pair passes of copy-pair function, otherwise copies apart when have copy ($copying) of text node within value element, in instance creates new alternative text value copy.

the copy-pair function determines whether copy original pair depending on if copying or not , creates new copy of original pair, performs recursive descent.