In Freedombase, all attributes are validated against their data type, every time an instance (record) is updated into a class (table) through Freedombase.

In the example below, we have also added a validation calculation, that will validate that the contents of the attribute are alpha. If any attribute within a class fails any kind of validation, then that instance will not be written into the Class. Instead, the instance will be displayed back to the user, with an appropriate error message.

For the sakes of demonstration, we will validate that any values entered into the STATE attribute on the STATE class are alpha only, ie cannot contain numeric values. In the Validation field for the STATE attribute, enter the calculation ALPHA(STATE). For the sakes of efficiency, enter 1 into the Validation Recurse field.

As with the previous derivation calculation, this is a very simple example of a validation calculation. More complex validation calculations can be created as needed. More complex calculations are covered in more detail further on in this tutorial.