gistfile1.rb

source = "<a xmlns:x='foo' xmlns:y='bar'><x:b id='1'/><y:b id='2'/></a>"
doc = Document.new source
doc.elements["/a/x:b"].attributes["id"]	                     # -> '1'
XPath.first(doc, "/a/m:b", {"m"=>"bar"}).attributes["id"]   # -> '2'
doc.elements["//x:b"].prefix                                # -> 'x'
doc.elements["//x:b"].namespace	                             # -> 'foo'
XPath.first(doc, "//m:b", {"m"=>"bar"}).prefix              # -> 'y'