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Hit "setup" and you will see a network for information flow related to fire emergencies in California. We assembled this from statutes in California, showing mandated linkages between agents (agencies, organizations & groups), for information flow related to fire. Yet the same general model could apply to any information flow network. Green shows uninformed nodes. When you hit setup you assign information to one node, randomly chosen.

Hit "go" then click on any node to give it information. See the information spread. Information spreads only in the direction of the arrows, because this is a directed network. Some nodes may be isolated from receiving information if there are no arrows towards it.

If you assign information to one node that is only a receiver of information, then the information will not spread.

The info-spread-chance slider only sets the chance per time step that information will spread from one node to another. You can think of this as representing the fact that information does not flow perfectly, and may fail. Yet because there are so many time steps in this model, information always eventually flows through nodes along the directions indicated.

Receiving nodes are not immediately aware of information a neighboring agent is trying to share. That's because all nodes only check their information every so often (like the frequency with which one checks their messages), set by the information checking frequency slider.

Delete a node at random to see how it affects spread of information. We want fire agencies to receive the information and indeed, they have the most in-links. However, nodes with the highest "betweenness"--those with the highest number of pathways crossing through, are the most crucial for the spread of information through a large proportion of the network.

You may try informing a node at random, rather than choosing a specific node to inform--just select "inform random node" and then hit "setup."

Note: You can make the network "spring," meaning nodes repel one another to avoid crowding while keeping more connected nodes relatively central. Thus when you "delete" nodes, the network takes a new shape. Hit "spring" and try deleting nodes.

Note: Once you hit "go" you can drag any node to move it.


Chris Keane developed this interactive information flow network. The California legal network itself was developed by Keane, with Patt Sweeney and her legal analysis team.

Netlogo: Copyright 2008 Uri Wilensky. All rights reserved.