The NetView window (see section 10.6 Network Viewer) is an essential window for us since it provides us with access to the network that we have created for learning the XOR problem. The NetView window has two sets of menus along with lots of pushbuttons and a display area containing a graphical display of the network. Lets take a look at the menus first. The left hand set of menus relate to the Network itself. The right hand set of menus relate to the NetView. The NetView is an object, actually a child of the Network, that provides a view of the Network. We can operate on either one, and we have two separate sets of menus.
The left hand menus allow access to the Network itself and the Networks' children: its .views and its .layers. Most of these menus have the same basic structure as we have already seen, but there is one new menu, namely the Actions menu. This menu allows us to perform actions on the network itself, such as removing things from it, initializing it, etc. Some of the other actions we can perform are accessible through the buttons to which we will turn in the next paragraph. The right hand menus allow us to access the NetView. This is indicated by the label View: on this set of menus. These menus operate on the visual display of the network, or any operation that interacts with the visual display (e.g., the Selections menu operates on things that are selected in the visual display).
The NetView itself, the main body of the NetView window, provides a
graphical depiction of our network. You can think of the layers of the
network arranged vertically, with the units within each layer laid out
on a two-dimensional sheet. The input layer is located at the bottom of
the netview, with the two input units arranged side by side. In
networks with many units per layer the units can be laid out in an X by
Y array. The hidden layer is next above the input layer, and we can see
the two hidden units, again laid out side by side. The output layer,
above the hidden layer, contains just a single unit, aligned to the left
of the netview. At present, each unit is displaying its activation, as
indicated by the depressed appearance of the act
button, together
with the yellow highlight. The activation is shown in color in
accordance with the color bar shown at the right of the NetView, and by
the numeric value printed on it. Either way we see that the activation
of all of the units is 0.
The Network has been initialized so that each unit has a random bias weight and so that there are random weights on the connections between the units. We can examine these biases and weights by displaying them on the netview. First, to look at the bias weights, we can click on the bias.wt button. Once we do this, the units will assume colors corresponding to their bias weights. The biases on the input units are not used and can be ignored.
We can also view weights either coming into or going out of a selected unit. The former are called 'receiving weights'. To view the receiving weights of the left hidden unit we first click on the button labeled r.wt. This activates the View button, and turns the cursor into a little hand, indicating that we may now pick a unit to view its receiving weights. We can now click on the left hidden unit, and its receiving or incoming weights are displayed on the units from which they originate; the selected receiving unit is highlighted. We see that this unit receives incoming weights only from the two input units, both somewhat positive. We can proceed to click on other units to view their incoming weights as well. Note that the input units have no incoming weights. To see the outgoing or 'sending' weights from a unit, we simply click the s.wt button, then click the unit whose sending weights we wish to view. You can verify that the values of the sending weight from the left input unit to the right hidden unit is the same value as the receiving weight to the right hidden unit.
Since all we've done so far is initialize the network's weights there isn't that much else we can look at at this point. However, if we click on the act button, the network will be set to display the activations of units later when we actually start to run the network. Do this now.