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 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