Who is the "you" in this? The party that knows the truth of your personal data isn't the same party that you want to rely on your personal data. The idea here

Who is the "you" in this? The party that knows the truth of your personal data isn't the same party that you want to rely on your personal data. The idea here is, say, the DMV in your state knows your age. But you don't want to show your driver's license credential which includes your home address and exact birthdate at a bar, because it's not their need-to-know. So you can ask the DMV to issue you with a "drinker's permit" which only has your photo and ageOver=21. A bar just validates you match your picture and knows you're of legal drinking age.