ValueStore valueStore =
fValueStoreCache.getValueStoreFor(field.getIdentityConstraint(), initialDepth);
setMayMatch(field, Boolean.TRUE);
XPathMatcher matcher = field.createMatcher(this, valueStore);
fMatcherStack.addMatcher(matcher);
matcher.startDocumentFragment();
return matcher;
} // activateField(Field):XPathMatcher
/**
* Ends the value scope for the specified identity constraint.