Preconditions

You use preconditions to check incoming data to determine whether a decision table can process the information. You can also use the preconditions to modify incoming data and define variables for the decision table. The variables are exclusive to the decision table.

The preconditions of a decision table are managed outside the decision table, typically in a separate dialog that you access from the decision table editor. You state preconditions as rules, for example:

definitions
   set ‘wealthy customer’ to a customer
      where the average monthly balance of this customer 
                                      is more than $1 000 000
if
   the state of residence of ‘wealthy customer’ is NY

These preconditions start by defining the variable wealthy customer. The preconditions then limit the scope of the rules in the decision table to customers who have an average monthly balance of $1 million, and reside in the state of New York.

The preconditions are tested before each rule in a table is executed. If an application presents data that passes the preconditions of a decision table, the data is tested by the preconditions before each rule in the decision table is executed. For example, if a table contains 10 rules, the preconditions can be tested 10 times.

Setting preconditions

To change the preconditions:

1. Click Preconditions in the decision table editor.
2. Define the preconditions in the rule editor.
3. Click OK to apply the preconditions.