RE: redefine and target namespace

> I thought the element 'b' was defined in the target namespace, but it
seems it has to be in no namespace.

Just as if you didn't use redefine, your local element declaration will only
be in the target namespace if you specify elementFormDefault="qualified" on
your xs:schema element. (Or, of course, form="qualified" on the local
element declaration itself, but no-one ever does that.) 

> Is it really the intent of the spec?

Yes. I've never heard an adequate explanation of why this extraordinary
decision was made, but in practice everyone changes the default by using
elementFormDefault="qualified".

Regards,

Michael Kay
http://www.saxonica.com/
http://twitter.com/michaelhkay