Support for Subgraphs is important to many different graphical applications. Subgraphs are user-collapsible nodes that contain graphs, supporting links within and across the subgraph boundaries.
That might include the ability to constrain nodes within "swim lanes" or regions of a diagram...
Swimlanes in a SwimmingPool
... or the ability to expand / contract groups of nodes like TreeApp:
The "Planogrammer" sample application illustrates several of these new features by allowing users to drag and drop products onto different displays, such as shelves and racks, with different move and snap-to behaviors appropriate to the different display types:
Planogrammer Sample Application