esource and shares 
rdfs:Class as its type with rdfs:Resource. The line 6 to 8 demonstrates that 
vin:Wine is added into the rdfs:subClassOf slot of vin:Zinfandel. Exactly, the 
superclass of vin:Zinfandel is refined from rdfs:Resource to vin:Wine, because 
it is directed, and rdfs:Resource as superclass of vin:Zinfandel is involved by 
the transitivity of subsumption through vin:Wine. Thus, the automatic 
redefinition in SWCLOS is possible and knowledge monotonously increases. The 
forward reference involv