Re: less-restrictive range and domain terms

Benja Fallenstein writes:
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 > Phil Dawes wrote:
 > |  > >
 > |  > > x:schnak rdfs:range aoeuii
 > |  > > =====>
 > |  > > x:schnak phil:rangeIncludes aoeuii
 > 
 > Let's recapitulate: "There is a triple with property x:schnak and value
 > of type aoeuii" seemed an appropriate interpretation of the second
 > statement above.
 > 
 > | Peter F. Patel-Schneider writes:
 > |  > Perhaps, but this doesn't follow from the intuitive meaning that
 > you said
 > |  > you were thinking of.  Either the intuitive meaning or the
 > inference rule
 > |  > are wrong.
 > |
 > | I'm not sure I understand.
 > 
 > This is about the 'edge case' of empty sets.
 > 
 > ~    x:schnak rdfs:range aoeuii
 > ~    "All triples with prop x:schnak have values of type aoeuii"
 > 
 > ~    x:schnak phil:rangeIncludes aoeuii
 > ~    "There exist triples with prop x:schnak have values of type aoeuii"
 > 
 > The first is true even if there are *no* triples with property x:schnak
 > at all. The second is not. That's why you cannot infer the second from
 > the first.


Ah - I understand now - 

Many thanks,

Phil