protected boolean testTagAt(DataContext data, PropertyKey node) {
String fullTagName = DataRepository
.createDataName(node.path(), tagName);
SimpleData sd = data.getSimpleValue(fullTagName);
return sd != null && sd.test();
}
protected void clearValueAt(DataContext data, PropertyKey node) {
String fullDataName = getDataName(node);
data.putValue(fullDataName, null);