About Constants
There are two types of predefined constants:
EMPTY_STRING.
NULL.
They can be used in decision table condition values, decision table assignment result values, decision tree condition values, decision tree assignment result values and event rule assignment result values.
If EMPTY_STRING is assigned to a parameter element in a condition value of a decision table or a decision tree, the condition is fulfilled if the parameter element contains an empty string as a value in a parameter instance at runtime.
If NULL is assigned to a parameter element in a condition value of a decision table or a decision tree, the condition is fulfilled if:
The parameter element is missing in a parameter instance at runtime.
The parameter element exists and contains null as a value in a parameter instance at runtime.
The superordinated parameter element is missing in a parameter instance at runtime.
Example
You work with a customer parameter that contains the parameter elements name, age and address, and the parameter element address contains the subordinated parameter elements street, street_number, zip and city. You assign the constant NULL to the parameter element customer.address.zip in a decision table condition value.
Then the condition is fulfilled if:
The parameter element
zip is missing in a specific instance of the
customer parameter at runtime.
The parameter element
zip exists but contains null as a value in a specific instance of the
customer parameter at runtime.
The superordinated parameter element
address is missing in a specific instance of the
customer parameter at runtime.
