Get prefix of XML namespace from URI - actionscript-3

Question

How can I get the prefix of a xml namespace from URI?
example:
<Name xmlns:tiger="http://www.census.gov">
</Name>
I've got the
"http://www.census.gov"
I want to get the prefix
tiger
How can I do this in Actionscript / Flex?
thx
EDIT
The answer doesn't work with this complex example:
<Name xmlns:tiger="http://www.census.gov" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://www.opengis.net/wfs" xmlns:wfs="http://www.opengis.net/wfs" xmlns:ows="http://www.opengis.net/ows" xmlns:gml="http://www.opengis.net/gml" xmlns:ogc="http://www.opengis.net/ogc" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:it.geosolutions="http://www.geo-solutions.it" xmlns:cite="http://www.opengeospatial.net/cite" xmlns:worldWS="worldWS" xmlns:sde="http://geoserver.sf.net" xmlns:topp="http://www.openplans.org/topp" xmlns:sf="http://www.openplans.org/spearfish" xmlns:nurc="http://www.nurc.nato.int" xmlns:solWS="solWS">
tiger:poly_landmarks
</Name>
I've got empty Array.
ANSWER MY OWN Q
for EDIT example
var xml:XML = <Name xmlns:tiger="http://www.census.gov" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://www.opengis.net/wfs" xmlns:wfs="http://www.opengis.net/wfs" xmlns:ows="http://www.opengis.net/ows" xmlns:gml="http://www.opengis.net/gml" xmlns:ogc="http://www.opengis.net/ogc" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:it.geosolutions="http://www.geo-solutions.it" xmlns:cite="http://www.opengeospatial.net/cite" xmlns:worldWS="worldWS" xmlns:sde="http://geoserver.sf.net" xmlns:topp="http://www.openplans.org/topp" xmlns:sf="http://www.openplans.org/spearfish" xmlns:nurc="http://www.nurc.nato.int" xmlns:solWS="solWS">
tiger:poly_landmarks
</Name>
var ns:Namespace = xml.namespace("http://www.census.gov");
if(ns.uri == "http://www.census.gov")
....

Answer 1

var xml:XML = <Name xmlns:tiger="http://www.census.gov"></Name>;
var ns:Array = xml.namespaceDeclarations();
trace(ns[0].prefix); //output: tiger
UPD for complex xml (output tiger as well):
var xml:XML = <Name xmlns:tiger="http://www.census.gov" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://www.opengis.net/wfs" xmlns:wfs="http://www.opengis.net/wfs" xmlns:ows="http://www.opengis.net/ows" xmlns:gml="http://www.opengis.net/gml" xmlns:ogc="http://www.opengis.net/ogc" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:it.geosolutions="http://www.geo-solutions.it" xmlns:cite="http://www.opengeospatial.net/cite" xmlns:worldWS="worldWS" xmlns:sde="http://geoserver.sf.net" xmlns:topp="http://www.openplans.org/topp" xmlns:sf="http://www.openplans.org/spearfish" xmlns:nurc="http://www.nurc.nato.int" xmlns:solWS="solWS">
tiger:poly_landmarks
</Name>
var nss:Array = xml.namespaceDeclarations();
for each(var ns:Namespace in nss)
{
if(ns.uri == "http://www.census.gov")
{
trace(ns.prefix);
break;
}
}