Selecione o valor do elemento xml no Oracle

select a.*
from   XMLTABLE(
         XMLNAMESPACES('urn:www.someSite.com/myModel' AS "ns"),
         '/*'
         PASSING my.myColumn           
         COLUMNS
           val  VARCHAR2(2000)   PATH '/a/ns:b/ns:c'
       ) a, myTable my;