Validating co-constrains in XML Schema 1.1 using xs:alternative

(Andrew Welch) Rather than mess around with loads of assertions to check your co-constraints, XML Schema 1.1 introduces the xs:alternative instruction which allows you to change the type used to validate the element based on some condition. Instead of defining one type and then adding assertions to check the variations, just define one type per variation, then assign that type based on the condition.