12. A rating system in the sense of point (1) of Article 142(1) of Regulation (EU) No 575/2013 should cover all those exposures where the obligors or facilities show common drivers of risk and credit-worthiness and fundamentally comparable availability of credit-related information. The PD and LGD model within a rating system may comprise various calibration segments. Where all obligors or exposures within the range of application of the PD or LGD model are jointly calibrated the whole scope of application of the model is considered one calibration segment.

13. Exposures covered by the same rating system should be treated similarly by the institution in terms of risk management, decision making and credit approval process and should be assigned to a common obligor rating scale for the purposes of Article 170(1)(b) of Regulation (EU) No 575/2013 and a common facility rating scale for the purposes of Article 170(1)(e) of that Regulation.