private void activateSelectorFor(IdentityConstraint ic) throws Exception {
Selector selector = ic.getSelector();
if (DEBUG_IDENTITY_CONSTRAINTS) {
System.out.println("<IC>: XMLValidator#activateSelectorFor("+selector+')');
}
FieldActivator activator = this;
XPathMatcher matcher = selector.createMatcher(activator);
fMatcherStack.addMatcher(matcher);
if (DEBUG_IDENTITY_CONSTRAINTS) {
System.out.println("<IC>: "+matcher+"#startDocumentFragment()");
}