docbook w3c schema and Xmetal 4

Hello all,

I am trying to use the docbook schema (DocBook W3C XML Schema 4.4b1) 
with Xmetal (3.1 and 4) but  am running into all kinds of errors that 
prevent me from getting started,: the error message is: "Importation of 
a schema with no target namespace is not supported".

Is this a known and fixable issue?, I do not have access to my docbook 
archive so i cannot search it,

Thanks for any pointers and tips,

Regards,

Gerrit Kuilder