When an element carries the attribute <code>xmlns=""</code>, the default namespace for that element and its descendants reverts to "no namespace": that is, unprefixed names are considered not to be in any namespace.
XML Namespaces 1.1 also introduces the option to undeclare other namespace prefixes. For example, if the attribute <code>xmlns:p=""</code> appears on an element, the namespace prefix ''p'' is no longer in scope (and therefore cannot be used) on that element or on its descendants, unless reintroduced by another namespace declaration.
