SAP Message 28137 - Object variable &1 is declared but not used

Diagnosis
If you define variables that are not used in a constraint or rule, thevariables are saved, but you see a warning message.
Object variable &v1& is declared in the OBJECTS section, but is notused again in the source code.
For example:
OBJECTS:
?x is_a (300)printer, <-- Not used again in constraint or rule
?y is_a (300)table