8. The versioned relational database system set forth in claim 7 wherein: the operations include a change propagation operation that propagates changes to or from a version in a workspace of the multiparent graph, the change propagation operation using the multi-parent graph to determine workspaces whose versions are affected by the change propagation operation.
15. The versioned relational database system set forth in claim 8 wherein: the change propagation operation is a refresh operation that propagates a change in a version in a non-leaf node in the multi-parent graph to a version in the leaf node in the multi-parent graph.