Input Nodes

So far, all the example models in this guide have been designed with simple input nodes that have constant values. The input nodes are the nodes on the ends of tree branches. They contain the basic input data on which a model operates. To examine a model's behavior with different input values you simply edit the input node definitions individually and recalculate. It is quite easy to transform these models into models that prompt users for input data.

Consider the model below. It calculates the monthly payment required on a home mortgage loan.

There are four input nodes: Price, Down Payment, Interest, and Term. If you want to find out what the mortgage payment will be using different interest rates, you edit the Interest node. However, if you had developed this model for someone else to use, and if the model were more complex, the user would not necessarily know which node values to change.

You can alter the model so that it is obvious which nodes are inputs and outputs, or you can have the model ask the user for all required information whenever the model is recalculated. This type of model can be developed by one person for others to use.