Assume that we want to display a message only if the value of the amountOwed data element is greater than zero. One approach is to use a script to examine the value of amountOwed and alter the show/hide property of the message field, depending on the value of the data element.
Alternatively, you could bind the data to a subform. Binding data to a subform is more efficient than binding data to a field, although both methods produce the same result. Here, we add the status element to the data structure and bind this element to a subform. The subform includes the message field and the amountOwed field. With the minimum count of the subform set to zero, the message appears only if the status element exists.
In the data context, the decision to add the status node to the data file should be done at generation time, only if the value is greater than 0. This technique moves the logic to determine whether a subform is required in the data context design.