Re: Handling multiple rdfs:ranges

On Tue, Feb 23, 2016, at 17:41, Peter F. Patel-Schneider wrote:
> 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.)
You're right, forgot [] ex:prop1 [].

> 
> >> 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".
> 
> Here is where we differ.  In my view, adding "expected" weakens the
> statement considerably.
> 
Right, "one of the possible types" was my interpretation, but something
may be considered as "expected" even if there is only one irrational
entity expecting it.

> 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.  

Could it be triples all the way down? Doesn't the justification chain
typically ends at some definitions in natural language?

> Worse, the phrases used there aregenerally quite informal.

This makes it difficult indeed.

Reto

Received on Tuesday, 23 February 2016 17:13:09 UTC