Everything is a Resource

Hi,

I have this problem with comprehending how entailment rules are 
constructed for RDFS concerning "everything is a resource".

There are rules rdfs4a and rdf4b which state that subject and object of 
every triple are resources.

These rules seem to me, however, as special cases of rdfs2 and rdfs3 
which are saying that subject/object of a triple can be assinged a type 
according to defined domain/range of a property in a triple. Only 
condition is that It would have to be given that for every property, its 
domain and range is class of all resources.

Btw.
It is noted in RDF Semantics in section 7.3.1 "Extensional Semantic 
Rules" that they have exactly this consequence (that domain and range of 
every property is rdfs:Resource). Although I don't see how it's possibly 
from rules that are listed, it's evident from extensional semantic 
conditions in section 4.2.

I would really appreciate if someone could explain rationale behind this 
to me.

Thank you very much.


Svatopluk Šperka