# fn:namespace-uri - XPath XQuery Reference

Returns the namespace URI part of the name of $arg, as an
               xs:anyURI value.deterministiccontext-dependentfocus-dependentdeterministiccontext-independentfocus-independentIf the argument is omitted, it defaults to the context node (.). The
            behavior of the function if the argument is omitted is exactly the same as if the
            context item had been passed as the argument.If the node identified by $arg is neither an element nor an attribute node,
            or if it is an element or attribute node whose expanded-QName (as determined by the
               dm:node-name accessor in the )
            is in no namespace, then the function returns the zero-length xs:anyURI
            value.Otherwise, the result will be the namespace URI part of the expanded-QName of the node
            identified by $arg, as determined by the dm:node-name accessor
            defined in ), returned as an
               xs:anyURI value.The following errors may be raised when $arg is omitted:If the context item is absent,
                  dynamic error If the context item is not a node, type error .