# Traverse Instance

The “Traverse Instance” function can be invoked by selecting an instance node in run mode, and selecting either “Traverse Instance” from the Network Menu, or from the popup-menu (brought up by a right-click with the mouse). This will open a new window containing a compiled version of the class from which the instance is derived (See figure 1).

Figure 1: A traversal frame for the Ann class in the Studfarm network.

The functionality of the traversal frame is very limited. Only operations concerning insertion and propagation of evidence are included.

Traversing instances can be very useful when working with OOBNs. In the main network (i.e., the network with the instance nodes which are to be traversed) there is no way of examining the structure of the instance nodes. The only way of interacting with the nodes in the instance is by clicking on the nodes in the belief bar, and this contains no structural information (except for encapsulating nodes in instances). By traversing the frame, this structure is revealed while still being able to insert and retract evidence. Obviously, recursive traversal is possible as well, so that any instances present in the traversal frame can themselves be traversed.