Re: Semantics TF: 'weak' transparency and entailments driven by reification

On 1/14/25 8:04 AM, Thomas Lörtsch wrote:
> Hi SemanticsTF-ers,
> 
> 
> maybe someone has a moment to explain to me in more detail what is going on with entailments on reified triple terms (or rather the lack thereof) - because the revelation during the last Semantics TF meeting before christmas that triple term reifications don’t support entailment really came as quite a shock to me (both the fact itself and that I seem to have missed it for quite some time), and it took me some time to wrap my head around it. As it stands I’m pretty sure I disagree with what Dörthe and Niklas said about the subject, so we probably will need to discuss this (probably not this week, as we’re still discussing triple terms themselves, but soon-ish, and I always need some time to process these issues).
> 
> 
> Niklas' example from the chat (https://www.w3.org/2024/12/20-rdf-star-minutes.html) was:
> 
>      :loves rdfs:subPropertyOf :knows .
>      :a rdf:reifies <<( :bob :loves :sue )>> ;
>          a :Lie .
> 
>      should not imply
> 
>      :a rdf:reifies <<( :bob :knows :sue )>> ;
>          a :Lie .
> 
> At first sight this sounds convincing. However, the example uses some kind of negation which can be a tricky subject in itself, so let’s try something more middle-of-the-road and take an example that just adds more detail:
> 
>      :loves rdfs:subPropertyOf :knows .
>      :a rdf:reifies <<( :Bob :loves :Sue )>> ;
>          :since :CarolsBirthdayParty .
> 
>      should not imply
> 
>      :a rdf:reifies <<( :Bob :knows :Sue )>> ;
>          :since :CarolsBirthdayParty .

I don't see that moving from a negated context, even a modal negated context, 
to a temporal one makes anything less tricky.

> 
> By intuition, that seems more convincing. However, the intuition might rely on a closed world assumption: when we say (in RDF) that Bob knows Sue since 2023, we’re not saying he didn’t know here in 2022.  Is that contrived? When it comes to reasoning, "normal" intuitions do not always hold. So, I’m still not convinced.
> 
> 
> What could be a more abstract description, what is "really" going on? It seems to me that the root of the problem is that the reifier refers to the more specific subtype, and - of course(!) - annotations on the subtype are not necessarily true of the supertype. This is also the case with standard triples. Take for example:
> 
>      <http://ex.org/GrumpyPerson>
>          rdfs:subClassOf <http://schema.org/Person> ;
>          a <http://ex.org/DifficultPerson> .
> 
>  From that we wouldn’t entail that
> 
>       <http://schema.org/Person>  a <http://ex.org/DifficultPerson> .
> 
> because what we said about the more specific <http://ex.org/GrumpyPerson> doesn’t necessarily apply to the more general <http://schema.org/Person> - that is how sub classes are defined. On the other hand we know that everything that is true about a <http://schema.org/Person> is also true about an <http://ex.org/DifficultPerson>. Now let’s apply that to triple terms:
> 
>      :loves rdfs:subPropertyOf :knows .
>      :a rdf:reifies <<( :Bob :knows :Sue )>> ;
>          a :Lie .
> 
>      _should_ (at least by my intuition) imply
> 
>      :a rdf:reifies <<( :Bob :loves :Sue )>> ;
>          a :Lie

The question is not whether this is intuitive, but whether it can be part of 
RDF.  So don't ask whether something should intuitively imply, but whether it 
should imply in RDF.

It is, however, the case that if something doesn't intuitively imply then it 
is unlikely that it should imply in RDF.

> This seems to work, and I guess that's because it respects the flow direction of inheritance in subproperty relations. In other words: it looks like applying entailment on triple terms is not the problem per se, it must just not be applied the wrong way round.
> Let’s check on the example that doesn’t rely on negation but just adds more detail:
> 
>      :loves rdfs:subPropertyOf :knows .
>      :a rdf:reifies <<( :Bob :knows :Sue )>> ;
>          :since :SuesBirthdayParty .
> 
>      should not imply
> 
>      :a rdf:reifies <<( :Bob :loves :Sue )>> ;
>          :since :CarolsBirthdayParty .
> 
> And it doesn’t since :knows doesn’t entail :loves.
> 
> So, aren't we okay? What is the problem with entailing reified triple terms as long as we observe the proper direction of entailment? Or what am I missing?

You are missing the issue of whether this sort of reasoning is part (or can be 
part) of RDF.

> 
> 
> Best,
> Thomas

peter

Received on Tuesday, 14 January 2025 15:24:31 UTC