It is the labels on the
links and the connections between the nodes that are significant, not the positions
of the nodes and links, nor the numbers on the nodes.
1 A complete command reference for mpv and the other tools appears in Appendix B.
2 In mpv, click on a node to select it. Then use the n key to step forward and p to step backward.
Systems with Finite Models 101
0
2
ShowTitles()
1
SelectMessages() ShowText()
4
SortByFirst()
3
SelectMessages()
SelectTopics()
SortByMostRecent()
6
ShowText()
5
SelectMessages()
SelectTopics()
ShowTitles()
7
SelectMessages()
SelectTopics()
SelectTopics()
Figure 6.4. Newsreader true FSM: state transition diagram drawn by mpv tool.
It can be helpful to view the graph produced by exploration even when you do
not have a precise question in mind, because it might reveal that the model program
does not behave as you intend. For example, you may see many more or many fewer
states and transitions than you expected, or you may see dead ends or cycles you
did not expect.
We recommend that you explore and view your model program as you develop
it, so you can check frequently that it behaves as you intend. There is no need to
finish the model program first; you can begin exploring as soon as you have coded
a few actions.
6.2.3 Interactive exploration and simulation
The mpv tool can also explore interactively, executing and displaying a fewtransitions
at a time, under the user??™s control.
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