XSD syntax, is it possible to implement an if else construct?

Question

XSD

The question is, is it possible to implement something like this:

Если элемент <frist_name>Вася</> то <last_name></> обязательно к заполнению.
Если элемент <frist_name>СуперВася</> то <last_name></> не обязательно к заполнению.

I read the doc, used Google, with my weak English, I realized that this cannot be done. But I would like to be 100% sure. Maybe someone knows the answer to this question and can immediately give an answer.

Answer 1

There are substitution groups. That is, we can say that either such content is valid, or such. I think this is a good example of using groups: stackoverflow.com/questions/39868769/xsd-element-s...
But are you sure you should use XSD for this task? This should also be a means of formal validation. That is, if your component received a valid XSD as input, it means that it can parse such a document. And even then you can conduct business validation, check invariants, etc.