Object key = node;
if (node instanceof FromDefinition) {
FromDefinition fromType = (FromDefinition) node;
key = fromType.getUriOrRef();
} else if (node instanceof ToDefinition) {
ToDefinition toType = (ToDefinition) node;
key = toType.getUriOrRef();
}
NodeData answer = nodeMap.get(key);
if (answer == null) {
String id = "node" + (nodeMap.size() + 1);
answer = new NodeData(id, node, imagePrefix);