The http://xml.org/sax/features/xmlns-uris feature "Controls whether, when the namespace-prefixes feature is set, the parser treats namespace declaration attributes as being in the http://www.w3.org/2000/xmlns/ namespace. By default, SAX2 conforms to the original "Namespaces in XML" Recommendation, which explicitly states that such attributes are not in any namespace. Setting this optional flag to true makes the SAX2 events conform to a later backwards-incompatible revision of that recommendation, placing those attributes in a namespace."