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Re: Handling multiple rdfs:ranges

From: Peter F. Patel-Schneider <pfpschneider@gmail.com>
Date: Tue, 23 Feb 2016 08:41:23 -0800
To: Reto Gmür <reto@wymiwyg.com>, semantic-web@w3.org
Message-ID: <56CC8BB3.2080308@gmail.com>
On 02/23/2016 08:24 AM, Reto Gmür wrote:
> On Tue, Feb 23, 2016, at 17:05, Peter F. Patel-Schneider wrote:
>> On 02/23/2016 07:31 AM, Reto Gmür wrote:
>>> [...]
>>>
>>> Granted, the semantics of :rangeIncludes are very weak (under OWA) but
>>> the fact that you can create contradictions with it shows that it's not
>>> completely meaningless.
>>>
>>> ex:prop1 s:rangeIncludes :Cat .
>>> :Cat owl:disjointWith :Dog .
>>> ex:prop1 owl:range :Dog .
>>>
>>> The above graph evaluates to false in every possible world, this is not
>>> the case if you omit any of the 3 triples, this shows that
>>> `s:rangeIncludes` is not a meaningless decoration.
>>>
>>> Reto
>>
>> I don't think that this follows from the semantics of :rangeIncludes,
>> even if
>> you augment schema.org semantics with disjointness.
> 
> In the example I also used "owl:range" to create what I thought is a
> contradiction.

OK, but I saw that.  (I actually missed that there are no values for ex:prop1.
 Without any such values you don't get a contradiction even if you made both
of the ranges be OWL ranges, and used OWL semantics.)

>> Perhaps one could also count the documentation of
>> rangeIncludes as authoritative as well.  So from
>> https://schema.org/rangeIncludes, rangeIncludes "[r]elates a property to
>> a
>> class that constitutes (one of) the expected type(s) for values of the
>> property" would also be part of the semantics of schema.org ranges.
> 
> I considered only this definition. And based on that I still think there
> is a contradiction, if the owl:range of a property excludes :Cat (which
> is expressed with the statements using owl-properties), :Cat cannot at
> the same time "be (one of) the expected type(s) for values of the
> property".
> 
> Reto

Here is where we differ.  In my view, adding "expected" weakens the statement
considerably.

Without any official formal semantics for schema.org or other guidance from
the schema.org people we are reduced to considering the meaning of English
phrases on the schema.org website.  Worse, the phrases used there are
generally quite informal.

peter
Received on Tuesday, 23 February 2016 16:41:53 UTC

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