using types from an included file in a different namespace

Hi all,
Maybe the subject is not very clear but I'll try to explain my question.
I have a schema file A.xsd including another file B.xsd (so in the same ns
as A.xsd), and B.xsd importing F.xsd (so in a differente ns). Can I use
types/elements defined in F.xsd from A.xsd?

It looks like XML Spy allows this, but Saxon produces this error:
"Cannot reference schema components in namespace http://myns as it has not
been imported".

What behaviour is correct?

Thanks you.

Regards,
Leo.