public void doSaveCoordinates() {
String xml = null;
XMLMemento memento = XMLMemento.createWriteRoot("graph"); //$NON-NLS-1$
for (Activity child : children) {
IMemento childMemento = memento.createChild(KEY_ELEMENT);
childMemento.putString(KEY_ELEMENT_TYPE, child.getInputName());
childMemento.putString(KEY_MODEL_CLASS, child.getClass().getSimpleName());
IDOMElement input = child.getInput();
IMemento structureMemento = childMemento.createChild(KEY_STRUCTURE);