Re: Handling multiple rdfs:ranges

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.


One can try to make guesses as to the semantics of schema.org (and I have),
and one can ask the schema.org people (and I have), but the data model at
https://schema.org/docs/datamodel.html appears to be the main thing that is at
all authoritative.  That document says for ranges that "each property may have
one or more types as its ranges. The value(s) of the property should be
instances of at least one of these types."  (I wonder what happens if a
property has no ranges.)  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.

Neither of these appear to be strong enough to infer a contradiction if a
value is known to not belong to any of the "ranges" of a property.


I had been looking at actual schema.org data from the web to find out how
schema.org ranges are used in practice.  It turns out that there are quite a
few violations of schema.org ranges.  However, this project is now in hiatus
due to lack of people resources to continue it.


Peter F. Patel-Schneider
Nuance Communications

Received on Tuesday, 23 February 2016 16:05:54 UTC