Simplify the following text for a Grade 15 native English-speaking person.
Original: Where nominal data must be used , the ideal is to use `` hard '' , objective criteria for assigning the classifications ( see Operational definition ) , such that different classifiers would produce the same assignments .
Simplified: Where data must need be used , the ideal is to use `` hard '' , `` objective '' criteria for assigning the classifications ( see definition ) , such that different classifiers would produce the same assignments .