# fn:namespace-uri-for-prefix - XPath XQuery Reference

Returns the namespace URI of one of the in-scope namespaces for $element,
            identified by its namespace prefix.deterministiccontext-independentfocus-independentIf $element has an in-scope namespace whose namespace prefix is equal to
               $prefix, the function returns the namespace URI of that namespace.If $element has no in-scope namespace whose namespace prefix is equal to
               $prefix, the function returns the empty sequence.If $prefix is the zero-length string or the empty sequence, then if
               $element has a default namespace (that is, a namespace node with no
            name), the function returns the namespace URI of the default namespace. If
               $element has no default namespace, the function returns the empty
            sequence.Prefixes are equal only if their Unicode codepoints match exactly.
<z:a xmlns="http://example.org/one" xmlns:z="http://example.org/two">
  <b xmlns=""/>
</z:a>fn:namespace-uri-for-prefix("z", $e)"http://example.org/two"fn:namespace-uri-for-prefix("", $e)"http://example.org/one"fn:namespace-uri-for-prefix((), $e)"http://example.org/one"fn:namespace-uri-for-prefix("xml", $e)"http://www.w3.org/XML/1998/namespace"fn:namespace-uri-for-prefix("xml", $e)"http://www.w3.org/XML/1998/namespace"