A,B,C,D Graded properties??

[Jason Huber]

I hear all the time about A-B-C-D properties. These letters are used as a guide to describe the condition and the quality of renter one should expect. I get that. My question is, Is this grading subjective or based on a certain criteria? Is it possible that my "B" graded property could be looked at as a "C" grade by someone else? Or, is it because said property has a certain set of characteristics it would be labeled factually in a certain grade. 

Would love to hear about if there is a guideline posted somewhere.