rcase-NameAndTypeOK.2: Error for the particle whose {term} is the element declaration 'aa....aa'. The element declaration's {nillable} is true, but the corresponding particle in the base type has an element declaration whose {nillable} is false.

This is an error for a particle whose item is the element declaration aa....aa. Nillable of the element declaration is true, but nillable of the element declaration of particle of the corresponding base type is false.