Every XMLType instance has a special internal "is validated" flag; The first successfull call of the member function XMLType.schemaValidate() will set this flag to 1 indicating that next such calls are redundand and should do nothing. If a given XMLType instance is made by a procedure that guarantees the match of the result to an expected schema then one can set this flag without running actual validation. It is also possible to reset this flag to 0 in order to force the next call of XMLType.schemaValidate() to perform a validation.
The function returns a new value of the flag.