Re: Handling multiple rdfs:ranges

On 02/26/2016 01:52 AM, Reto Gmür wrote:
> 
> On Thu, Feb 25, 2016, at 06:18, Pat Hayes wrote:
>>
>> On Feb 23, 2016, at 10:24 AM, Reto Gmür <reto@wymiwyg.com> 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.
>>>>
>>>> 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".
>>
>> Of course it can. It only follows that the values of this particular
>> property are all in some other part of the range. According to the
>> schema.org definition of rangeIncludes, this is quite permissible. 
> 
> I'm not getting you.
> 
> from
> 
> (1) :Cat owl:disjointWith :Dog .
> (2) ex:prop1 rdfs:range :Dog .
> 
> It follows that: (3) "no value of the property ex:prop1 can be an of
> type :Cat".
> 
> Do we agree till here?
> 
> (4) ex:prop1 s:rangeIncludes :Cat 
> 
> means: (5) "The class :Cat is an expected type for values of the
> property ex:prop1"
> 
> Do you agree that (5) follows from (4) when using the definition from
> http://schema.org/rangeIncludes?

No.  This sentence reads as if each expected type for a property is the type
of all values of the property.  This is not the case at all in schema.org.

Even the slightly weaker statement at https://schema.org/rangeIncludes is not
suitable.  The wording there "Relates a property to a class that constitutes
(one of) the expected type(s) for values of the property." also reads as if
each expected type is supposed to be a type of all values of the property.

> Agreeing to both (4) and (5) boils down to:
> 
>  - :cat is an impossible type for values of the property ex:prop1
>  - :cat is an expected type for values of the property ex:prop1

Not exactly.  "Impossible" is a very strong word here, even stronger than
contradictory.  It is certainly possible for a value of a property to have a
type that contradicts the range of the property.  It just triggers a
contradiction (or maybe even something with even less import), which does what
contradictions (or whatever) do in the setup one is currently working in.

> Using the first definition of "Expect" from the oxford dictionary as
> "Regard (something) as likely to happen", I think there is a
> contradiction between asserting that something is impossible and that
> something is expected.

Certainly there would be something odd going on in an extended schema.org
setup if one of the rangeIncludes of a property were disjoint from a true
range of the property.  I do not, however, believe that this oddness is
anything near a strong contradiction (i.e., something that causes all
information to be meaningless).

> 
> I would really like to learn where you think my reasoning is wrong.
> 
> Cheers,
> Reto
>  
>> If you disagree, please suggest how to express the schema semantics as a
>> precise model-theoretic condition in such a way that it produces the
>> contradiction you expect. 
>>
>> Pat Hayes
>>
>>>
>>> Reto

peter

Received on Friday, 26 February 2016 13:28:40 UTC