How to save layout?

I am using GoXam and implemented GraphLinksModel. I have a diagram with links and nodes. User can manually move nodes and links.But whenever user closes the diagram and opens again, changes are not getting preserved. How do I preserve those changes when user makes any change without creating or using any external database?

You can have a look at the GoXam intro document here
Save operation is described on page 86 (XML format)