Re: [ANN] Working drafts by SW Best Practices group -- request for comments

> The explanation that I often found useful is to think of classes as sets 
> of their instances (so, the class of Lions is a set of all lions). Then 
> subclass-of is a subset relationship  (the set of African lions is a 
> subset of a set of all lions). instance-of is set membership: Simba is a 
> member of the set of African lions (and lions, of course).

Thanks! Extending "is a" to "is a subset" (rdfs:subClassOf) or "is a 
member" (rdf:type) makes the distinction perfectly clear.