I have a diagram where a user can add couple of composite nodes and have one or multiple link to/from each node. After adding the nodes, the user can rearrange the diagram by dragging nodes and links.

II want o retain the state of this diagram in the database. And when the user loads the screen again, I want to draw to diagram as it was previously arranged, what are the properties I need to serialize and save? All nodes are of same size so I do not need to save the width and height. Other than these, what can I save to persist the arrangement of nodes and links.