We have already seen how business logic can be added using calculations, for example converting the STATE attribute to uppercase, validating that the STATE value entered was alpha, and generating a unique customer number when no customer number was already set.

However, these examples are among the most simple calculations possible; they only involve one or two functions or statements, and they only refer to the data of the attribute that they are attached to. In a full system, the calculations would be much more complex, ie they would include many more functions or statements in each calculation; and they would also refer to other attributes within the current instance, and data in other, directly or distantly related instances.

Please note that it is also possible to apply business logic using custom code (subroutines or functions) in Freedombase; however, applying business logic using custom code (suboutines or functions) is covered in a separate tutorial. This tutorial only covers applying business logic using derivation, validation, and error message calculations.