RDF semantics: problems with entailment rules rdfs5 and rdfs9

Two rdfs entailment rules do not seem to be stated
in sufficient generality.
This is indicated by the following two counterexamples
to the rdfs entailment lemma.

Example: graph G consists of triples
  x subPropertyOf y
  y subPropertyOf z
where x y and z are blank nodes.
In this case the semantics shows that
G rdfs-entails the triple
  x subPropertyOf z
However this triple is not derived by rule rdfs5,
since this rule requires x y and z to be URIs.


A similar problem occurs with rule rdfs9.

Example: graph H consists of triples
  x subClassOf y
  z type x
where z is a blank node.
According to the semantics, H rdfs-entails the
triple 
  z type y
This triple is however not derived by rule rdfs9
since this rule requires z to be a URI.


Herman ter Horst