xml schemas: Is there a way to bind key and keyref definitions to a complex type ?

Hello,

Up to now, I defined key, unique and keyref constraints on a element
definition.  I now have to define other elements of the same type as
the existing element.

So I've created a complex type with the content of the existing
element.  I would like to associate the key and keyref constraints to
the type, because these constraints must always be obeyed, and so that
they can be shared beween all elements referencing this type.

Is there a way to do that ?

Thanks for your replies

Vincent De Groote