The CBB has decided to allow only the foundation approach for corporate, sovereign and bank asset classes. However, banks are required to adopt the advanced approach for retail asset class. Under the foundation approach, as a general rule, banks provide their own estimates of PD and rely on CBB's estimates for other risk components. Under the advanced approach, banks provide more of their own estimates of PD, LGD and EAD, and their own calculation of M, subject to meeting minimum standards. For both the foundation and advanced approaches, banks must always use the risk-weight functions provided in this chapter for the purpose of deriving capital requirements. The full suite of approaches is described below.