# Node Inspector¶

When debugging a counterexample or when using probe, FDR allows an individual node (i.e. state) to be inspected in order to allow the actual structure of the node to be understood. The node inspector can be launched on any state in Probe by selecting a row, right-clicking and then selecting Inspect Node in the resulting menu. To launch the node inspector from the Debug Viewer, hover over the desired state and select Inspect Node in the window that appears. For example, suppose the counterexample shown as part of the Debug Viewer is being viewed and that the very first node of the implementation row is hovered over (i.e. the blue node on the SYSTEM line). Clicking Node Inspector in the resulting window will result in the following being displayed:

Clicking on Expand All will result in the full node structure of the selected node being displayed, as shown below:

The above indicates that the selected node is an alphabetised parallel of three alphabetised parallels, the first of which is a parallel of the weak bisimulation of PHIL(0) and the weak bisimulation of FORK(0). Hovering over the nodes in the window will display information various information, such as the synchronisation sets in use. Unknown nodes are indicated using a ?. Note that hovering over the node will reveal some information about it, such as which state machine the node is a member of (if known).