Saxon

Using Saxon 9.8.0.4 HE or EE and an XQuery from the command line where I try to recreate the root element from the input document, then add two nested elements with direct element constructors to contain some descendants elements of the original document I get duplicated namespace declarations on the descendant elements.

Here is a reduced test case:

declare namespace output = "http://www.w3.org/2010/xslt-xquery-serialization";
declare default element namespace "http://example.com/ns1";
declare option output:indent "yes";

/*/element {node-name()} {
  let $root := . return in-scope-prefixes(.)!namespace {.} {namespace-uri-for-prefix(., $root)},
  @*,
  

  
  {
    //item
  }
  
  
}

A sample input document is

	
		a
		b
	

The result I get with Saxon is

   

      
         a
         b
      
   

so the @item@ elements have @xmlns:xsi@ namespace declarations they don't need.

Using XmlPrime or Altova XMLSpy the result is simply

  

    
      a
      b
    
  

so this seems some oddity of Saxon.

Interestingly enough, when trying to reduce the problem a bit more to only have on direct element constructor

declare namespace output = "http://www.w3.org/2010/xslt-xquery-serialization";
declare default element namespace "http://example.com/ns1";
declare option output:indent "yes";

/*/element {node-name()} {
  let $root := . return in-scope-prefixes(.)!namespace {.} {namespace-uri-for-prefix(., $root)},
  @*,
  
  {
    //item
  }
  
}

Saxon gives the same result as XmlPrime or Altova and the @item@ elements don't have the additional namespace declarations:

   
      a
      b