Complex types can be restricted by means of an ``++xs:restriction++`` element. But ``++restriction++`` is anti-inheritance: the derived type has less information than the base type. Further, restriction causes the redefinition of the complex types elements and attributes, which leads to fragility in your XML schema; any change to a super type will require corresponding changes in all restricting subtypes, even those in other schemas. For example, if the base type defines a mandatory "color" element of type ``++xs:int++``, the restricting type must also define a "color" element whose type cannot be, say, ``++xs:string++``.
``++xs:extension++``, on the other hand, allows the extending element to inherit the base class' elements and add new ones.
