Models are created in MSBNX as new model documents. Once the empty document window appears, you can add variables and dependency arcs for your model.
By default, variables (or nodes) are created without prior probability distributions. You can easily and automatically supply uniform distributions of different kinds at any time.
After the applications loads, you can click the "new document" button on the main application toolbar. An empty diagram document is created and given the default name model0. (The document is shown maximized here.)
To create the elliptical nodes that represent random variables, right click anywhere in the diagram to activate the diagram context menu. Choose "New Node..." from the menu. An edit box will appear on the diagram with a default name for the new variable and you can enter a new name.
When you strike the Enter key, the new node appears.
To create a conditioning arc between two nodes, do the following steps.
Click the left mouse button anywhere on the canvas. This de-selects any selected nodes or other objects.
Position the mouse button in the ellipse representing the parent variable.
While holding down the control (CTRL) key, also hold down the left mouse button and drag the mouse into the node representing the child variable.
By default, MSBNX will create a discrete distribution for every node created. You can change this behavior using the diagram window context menu. You have the choice of automatically creating standard discrete distributions, causally independent distributions or no distribution.
When dependency arcs are added or removed, the dimensionality of the distribution of the child node is changed accordingly.