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Re: Handling multiple rdfs:ranges

From: Reto Gmür <reto@wymiwyg.com>
Date: Wed, 02 Mar 2016 09:14:22 +0100
Message-Id: <1456906462.43449.537093538.0395AF8F@webmail.messagingengine.com>
To: Pat Hayes <phayes@ihmc.us>
Cc: David Booth <david@dbooth.org>, semantic-web@w3.org


On Wed, Mar 2, 2016, at 05:45, Pat Hayes wrote:
> 
> On Feb 29, 2016, at 2:50 AM, Reto Gmür <reto@wymiwyg.com> wrote:
> 
> > On Mon, Feb 29, 2016, at 03:04, David Booth wrote:
> >> On 02/26/2016 06:04 AM, Reto Gmür wrote:
> >>> Sure, still I think that schema:rangeIncludes is not meaningless (as it
> >>> restricts the rdfs:range statements that are possible) and that
> >> 
> >> Under the standard open world assumption (OWA) I do not think it is 
> >> correct to say schema:rangeIncludes *restricts* anything.  Bear in mind 
> >> that given the statement:
> >> 
> >>   :p schema:rangeIncludes :Cat .
> >> 
> >> one could always add an arbitrary additional class to the property's 
> >> "expected type(s)" by adding another statement like:
> >> 
> >>  :p schema:rangeIncludes :Dog .
> >> 
> >> Therefore, the original statement cannot be *restricting* anything 
> >> (under the OWA).
> > 
> > I did not say that it restricts the possible values of the properties,
> > but I'm saying that it restricts the possible rdfs:range statements that
> > are possible without creating a contradiction.
> > 
> >> 
> >> Personally, I think a reasonable way to interpret its meaning is that it 
> >> says 'there exists an individual :d such that :d rdf:type :Dog'.
> >> 
> >>> it has
> >>> some pragmatic usefulness such as when building editors that suggest
> >>> values for a specific property.
> >> 
> >> Agreed.  And it's also useful if you're doing closed world reasoning.
> > 
> > Well, even if you're closing the world I'm not sure you can do reasoning
> > about the instance data based on this property.
> > 
> > I claim that for something to be expected it must be possible, based on
> > this one can create a contradiction with statements of necessity
> > expressed with rdfs:range.
> 
> Nothing in the RDFS namespace can express anything about necessity. RDFS
> is not a modal logic. 

Well, According to the Necessitation Rule, any theorem of logic is
necessary (⊢ p →⊢ ◻ p). 

So if - as you do - agree that p rdfs:range t and x p y together entail
y rdf:type t, you cannot at the same time state that it is not
*necessary* for y to be of rdf:type t when p rdfs:range t and x p y,

Reto

> 
> Pat Hayes
> 
> > 
> > However, I don't think that only what is expected is possible. So even
> > if we know that only :Cat and :Dog are expected the unexpected :Mouse is
> > still possible.
> > 
> > Reto
> > 
> > 
> 
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Received on Wednesday, 2 March 2016 08:14:47 UTC

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