W3C home > Mailing lists > Public > semantic-web@w3.org > March 2016

Re: Handling multiple rdfs:ranges

From: Pat Hayes <phayes@ihmc.us>
Date: Wed, 2 Mar 2016 22:17:44 -0600
Cc: David Booth <david@dbooth.org>, semantic-web@w3.org
Message-Id: <092B3F35-FC00-41E8-A27D-F180B21898CD@ihmc.us>
To: Reto Gmür <reto@wymiwyg.com>

On Mar 2, 2016, at 2:14 AM, Reto Gmür <reto@wymiwyg.com> wrote:

> 
> 
> 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). 

You have to be very careful when citing this rule. It is a valid rule of *some* *modal* logics, not a generally valid principle of reasoning. It is not an inference rule in all modal systems. And even for those systems in which it is used, it applies to logical derivability *in that same system*, not derivability in (for example) RDFS. 

> So if - as you do - agree that p rdfs:range t and x p y together entail
> y rdf:type t,

They do so in RDFS and OWL, yes. 

> 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,

I can, and do, claim this; since (to repeat) neither RDFS nor OWL are modal logics, so the question of whether some RDFS or OWL statement is or is not *necessary* is meaningless. Or at any rate, it is meaningless until you or someone else provides a semantics for the appropriate modal extension of RDFS or OWL in which these assertions can be meaningfully stated. 

Pat

> 
> 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
>>> 
>>> 
>> 
>> ------------------------------------------------------------
>> IHMC                                     (850)434 8903 home
>> 40 South Alcaniz St.            (850)202 4416   office
>> Pensacola                            (850)202 4440   fax
>> FL 32502                              (850)291 0667   mobile (preferred)
>> phayes@ihmc.us       http://www.ihmc.us/users/phayes
>> 
>> 
>> 
>> 
>> 
>> 
> 
> 

------------------------------------------------------------
IHMC                                     (850)434 8903 home
40 South Alcaniz St.            (850)202 4416   office
Pensacola                            (850)202 4440   fax
FL 32502                              (850)291 0667   mobile (preferred)
phayes@ihmc.us       http://www.ihmc.us/users/phayes
Received on Thursday, 3 March 2016 04:18:16 UTC

This archive was generated by hypermail 2.3.1 : Thursday, 3 March 2016 04:18:20 UTC