Filtering XML attributes (fn:node-name vs. fn:name)

Question

Using XQuery (in eXist-db 2.2), I am trying to process a set of XML elements and remove a single attribute from each element in the result set.

Example XML:

<results xmlns:abc="http://example.org">
    <abc:element1 abc:selected="false" type="Class"/>
    <abc:element2 abc:selected="false" type="Property"/>        
</results>

The attribute to be removed is @abc:selected . My question is, what is the difference between filtering an attribute set by fn:name vs. fn:node-name, when the attribute has an xs:QName?

If I use fn:node-name and compare to the xs:QName of the attribute, then @abc:selected is not removed.

XQuery:

for $r in $results
let $name := node-name($r)
return
    element {$name} {
        $r/@*[node-name(.) != xs:QName('abc:selected')]             
    }

Result:

<results xmlns:abc="http://example.org">
    <abc:element1 abc:selected="false" type="Class"/>
    <abc:element2 abc:selected="false" type="Property"/>        
</results>

However, if I use fn:name and compare to the string value of the attribute, then @abc:selected is successfully removed.

XQuery:

for $r in $results
let $name := node-name($r)
return
    element {$name} {
        $r/@*[name(.) != 'abc:selected']
    }

Result:

<results xmlns:abc="http://example.org">
    <abc:element1 type="Class"/>
    <abc:element2 type="Property"/>        
</results>

What is the difference here? Why doesn't the first approach, with fn:node-name and xs:QName, work as I expect it to?

Answer 1

Looks like that isn't the proper way to create the expected xs:QName instance. This expression xs:QName('abc:selected') is throwing error "No namespace declared for prefix abc" for me (tested in BaseX).

You can use fn:QName() which return xs:QName instance instead, and that should properly remove abc:selected attributes :

for $r in $results
let $name := node-name($r)
return
    element {$name} {
        $r/@*[node-name(.) ne QName('http://example.org', 'selected')]             
    }