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.
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