SAP Message 28136 - Characteristic variable &2 (facet &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.
The variable for the characteristic facet pair (for example, DOMAINCOLOR) of an object is declared in the OBJECTS section, but is not usedagain:
OBJECTS:
?x is_a (300)printer
where ?dc = domain color