rdfs:subClassOf and XSD derivation by restriction

Suppose I have two XML Schema simple types that are suitable 
for use with RDF, one of which is derived by restriction 
from the other.  A simple example might be xsd:integer which 
is derived from xsd:decimal.

These are both datatypes in RDF, that is, we can say:

   xsd:decimal a rdfs:Datatype .
   xsd:integer a rdfs:Datatype .

And RDF Schmea tells us that all instances of rdfs:Datatypes 
are subclasses of rdfs:Literal, so:

   xsd:decimal rdfs:subClassOf rdfs:Literal .
   xsd:integer rdfs:subClassOf rdfs:Literal .

My question is this: can I use the fact that the xsd:integer 
simple type derives by restriction from xsd:decimal to say 
that there is a rdfs:subClassOf relation between them?  I.e. 
is the following true?

   xsd:integer rdfs:subClassOf rdfs:decimal .

Intuitively it seems like it ought to be, but I'm struggling 
to find chapter and verse saying this is so.

The examples in §7.2.1 of RDF 1.1 Semantics tells us that 
any valid statement of the form

   ex:a ex:p "sss"^^xsd:decimal .

D-entails

   ex:a ex:p "sss"^^xsd:integer .

And §2 of RDF Schema 1.1 says "If a class C is a subclass of 
a class C', then all instances of C will also be instances 
of C'", but it does not say the converse is true.  All 
instances of xsd:integer are also instances of xsd:decimal, 
but can we say xsd:integer is a subclass of xsd:decimal?

Richard