 Okay, so this session is about the validation rules. So we are still talking about identity data. The validation rules is about the data entry form validation. So, yeah, in GTK, we have the validation rule engine that can evaluate the evaluation rules, but always in the context of data entry form. It means this engine is not intended to be used to evaluate validation rules across the whole system, but only those validation rules that are triggered in the data entry form. You know these validation rules, there's a bottom in the data entry form in web that says RAM validation. So these validation rules are those ones. So the good thing here is that this validation rule engine uses the same parser of the expression than the backend. So this is something that is quite new. This was done like one year ago. In this test, too, there is a common parser of the expressions, the expressions that are used by the validation rules or by the program indicators, by the indicators also, by the program rules as well. So all those expressions are being parsed by the parser that is served between the backend and Android. So we could expect the same result in the backend and Android. The validation rule, the validation engine is in the validation module to trigger the validation of a particular data set instance. You only have to call the validate method like this. Okay, what about the result? The result of the validation method is a list of validation errors. So when you execute this method, what you get is a list of errors and each error contains some information, some context information about the error to make it easy to identify. So for example, it includes the validation rule that triggered the error. Then some information about both sides. You know that the validation rule is composed of two sides, the right side and the left side, and an operator. You can say that this part should be read there or equal to that part. So the etiquette also evaluates both parts and includes this evaluation in the result. So you can, for example, print something more meaningful to the user. It also includes the list of data element operand so you can highlight in the data entry form the data elements that are involved in this validation rule. Also the evaluative value, the display expression, it means each side of the evaluation rule but in a human-readable way. And also the evaluated expression. So as an example about this, you can print to the user some descriptive feedback. For example, total population should be greater than under 5 population. Or you can print to the user the values. Assuming that in this case total population is 500 and under 5 is 800, so this is not true. Or, for example, the formula, the regenerative, what is called the regenerative expression. And finally, you have the UIDs of the data element that are involved in the evaluation rule. So you can highlight in the data entry form those values that have caused the error. So that's all about the theory.