Bayesian Belief and Decision Networks |
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There are two ways to create a problem in the Bayes Network Applet.
Load A Sample Graph
This is the way to load a prebuilt Bayes graph. You can load from a set of sample problems, or load from a URL.
On the menu bar, select File->Load Sample Graph. A dialog will pop up with a choice of sample problems. Choose one.
On the menu bar, select File->Open Location. Type in the URL of the graph, and click load.
Create a network manually
Click the Create mode tab to display the Create panel. Click on the Create Node radio button and then click on the canvas. A dialog will pop up to ask the user what the node's name is and what is the domain of the node. Click 'Done' to create the node. Place additional nodes in this manner. To create arcs, click the Create Arc radio button and click on a node to define the starting point of that arc. Click on another node to define the end point of that arc. Arcs define probabilistic dependencies. To modify a node's probabilities, click the Modify Probability Table radio button and click on the node to be modified.
If the user wants to create a Decision Network (as opposed to a Belief Network), he or she should go to Query Control Options->Show Decision Net Controls. This will allow the user to set the node type as normal, decision, or value while creating nodes.
Click the Solve mode tab to go to Solve mode. Click the Query Node radio button. If the network is a Belief Network, one can query nodes immediately. However, if it is a Decision Network, some nodes (particularly decision nodes) cannot be queried until the network is optimized.
There are two ways to solve a query. To switch between modes, go to Query Control Options->Query Modes, and select either Brief Query Mode, Verbose Query Mode, or Prompt For Query Mode. If Prompt For Query Mode is selected, every time a query or optimization problem is solved, a dialog will pop up prompting the user to select either Brief or Verbose Query mode.
Brief Query Mode. Just click on a node after depressing the Query Node radio button. This will solve for the probabilities of the domain of the node, and will pop up a dialog informing the user of the results of the query. For Decision Nets, clicking on the Optimize Decisions button will optimize the decision nodes.
Verbose Query Mode. Clicking on a node after depressing the Query Node radio button will pop up a new canvas where the user can manually do variable elimination.