With a graph model, you can use already-built graphs, nodes, and links that have been developed without Views and apply the layout algorithms of Views. The graph model provides the basic, generic operations for performing the layout. A subclass must be written to adapt the graph model to specific graph, node, and link objects. This subclass plays the role of an “adapter” or bridge between the application objects and the graph model. This often makes it much easier to add graph features to existing applications.

Figure 5.1 shows the relationship between the graph model and graph layout algorithms, Views graphers, non-Views graphers, and manager views.

You can see from this diagram that instead of using a concrete graph class such as IlvGrapher directly, the layout algorithms interact with the graph via the graph model. This is the key for achieving a truly generic graph layout framework. Note that the use of an IlvView to display the result of the layout is not mandatory.