rule
xmlns-change condition? local-scope
A markup rule that fires when the namespace name of the current element is different form the namespace name of its parent. For the top level element, xmlns-change rules fire if the namespace name is not the empty string.
These rules require a %c or suppress action. They wrap the rule selection of the element rule for the element that caused the namespace change. In other words, the %c in the xmlns-change rule causes rule selection to take place for the element in the new namespace.
xmlns-change when xmlns-name = "www.some-uri.org/authors.xml" using group "authors" output "%c" group "authors" element #base "name" ...