Parent Down Tree-Grid

Hi Isomorphic,

I'm trying to figure out how to use the TreeGrid to suit my purposes.

The documentation and showcase provide plenty of examples of a TreeGrid arranged where the tree is bottom-up, where the leaves have references to a single parent object.
I'm looking for examples where the tree is top-down instead.

I have a hierarchy I want to represent where each node has a list of multiple children, but it is actually possible for a child to have multiple parents.

The following example looks promising. In particular the TreeGrid is bound to with a Datasource provided by XML, and is loaded on demand.
Could you provide an example that is top-down instead of bottom-up.
http://www.smartclient.com/smartgwt/showcase/#tree_databinding_ondemand

My problem with this example is that the entire hierarchy needs to be solved at display time, and it doesn't show how to connect it to a datasource: http://www.smartclient.com/smartgwt/showcase/#tree_databinding_children_arrays

Thanks,
Walker