Another challenge of modeling market risk is choosing and validating the appropriate models. Market risk models can be classified into different types, such as value-at-risk (VaR), expected shortfall (ES), stress testing, or scenario analysis. Each type of model has its own advantages and disadvantages, depending on the purpose, scope, and complexity of the market risk measurement. For example, VaR is widely used to measure the maximum loss that a bank can expect to incur over a given period and confidence level, but it does not capture the tail risk or the severity of losses beyond the VaR threshold. ES, on the other hand, measures the average loss that a bank can expect to incur in the worst cases, but it is more difficult to estimate and backtest. Moreover, market risk models may have different assumptions and parameters, such as distribution, correlation, volatility, or sensitivity, which may affect the accuracy and reliability of the models. Therefore, banks need to select the models that best suit their objectives and risk profiles, as well as to validate the models regularly and rigorously, using both quantitative and qualitative methods.