W3C home > Mailing lists > Public > public-vocabs@w3.org > April 2014

Re: How to avoid that collections "break" relationships

From: Peter F. Patel-Schneider <pfpschneider@gmail.com>
Date: Sat, 12 Apr 2014 18:07:11 -0700
Message-ID: <5349E33F.7080705@gmail.com>
To: Ruben Verborgh <ruben.verborgh@ugent.be>
CC: Markus Lanthaler <markus.lanthaler@gmx.net>, Pat Hayes <phayes@ihmc.us>, Linked Data community <public-lod@w3.org>, W3C Web Schemas Task Force <public-vocabs@w3.org>, Dan Brickley <danbri@danbri.org>

On 04/12/2014 05:20 PM, Ruben Verborgh wrote:
> Hi Peter,
>
>> Ok, I describe ex:BaseballPlayer as
>> ex:BaseballPlayer owl:equivalentClass _:x .
>> _:x owl:intersectionOf ( ex:Person  [ owl:onProperty ex:plays; owl:hasValue ex:Baseball ] )
>>
>> Is this RDF?
> Yes.
I would say that this is OWL in RDF clothing.

>> Should all consumers of RDF understand all of this?
> Yes, depending on your interpretation of "understand".
> All of them should parse the triples. This is where RDF ends.
This I totally disagree with.  RDF is much more than just triples. RDF  
includes a meaning for triples.
>
> Those that can interpret OWL will be able to infer additional things.
> This is OWL and not part of the RDF model
> (and thus also not extending the RDF model).
>
>      <h1>Baseball player</h1>
> doesn't extend HTML.
> It just applies HTML to describe a baseball player.

As using ex:BaseballPlayer doesn't extend RDF.

However, using owl:disjointWith as a predicate in triples, and expecting it to 
have some relationship to disjointness of RDF class extensions, is an 
extension of RDF.
>
>>> No, quantification is not part of RDF.
>> Why not?
> It is not in the spec.

But you appear to be using only part of the RDF spec.  Why just that part and 
not the whole RDF spec?  If *you* leave parts out, surely it is just as 
legitimate for *'me* to add parts.

>
>> I could certainly define an encoding of quanfification in RDF and use it to define predicates.
> You indeed can.
>
>>> Predicates may not influence non-related triples,
>>> however, other triples might be influenced through a cascade of relations.
>> Why not?  I can define predicates however I want, after all?
> Because, by definition of "related",
> if your predicate is defined to influence a certain (kind of) triple,
> that triple is related to the usage of the predicate.

Sure, but if I can add things to the RDF spec, then I could add something like:

The triple <a> <b> <c> means that all subclassOf relationships are strict.

>
>>>> What does using owl:differentFrom in RDF commit you to?
>>> It says that two things are different.
>>> Clients that can interpret this predicate can apply its meaning.
>>> This application does not change the model.
>> What model?
> The RDF model.
>
>> Do  you mean that all you care about is the abstract syntax?
> No.

But, but, but, isn't that what you said above?  All that counts is triples, 
i.e., the abstract syntax.
>
>> What about rdf:type?  What about rdfs:domain?  Do all consumers of RDF need to commit to the standard meaning of these predicates?
> Yes.

But this goes beyond triples.
>
>>> RDF is just the model. Giving a predicate meaning is not extending the model.
>>
>> How so?  What else is giving a predicate meaning besides extending the  model?
> It defines something on top of the model.
> Building a home with bricks does not extend the bricks; it uses them.

Yes, sure, which is why using rdfs:domain to infer rdf:type triples is not 
going beyond RDF(S).  However, using owl:sameAs as equality and inferring 
other triples from this is going beyond RDF(S).  It's just like turning a 
little brick into a long I-beam - you are no longer working with a little brick.
>
>> I am really struggling to understand your view of RDF.
> Likewise. But maybe further discussing this doesn't really help the community.
> My view on RDF works for what I want to do and in my opinion, it's by no means an unreasonable view.
> But there might be other views… and that might just be fine.

Well that's a bit debatable.  Standards, even W3C standards, are there so that 
there is commonality of understanding.  If different people take different 
views of RDF, then its utility is weakened, particularly if everyone still 
thinks that they are all using the same thing.

My view is that getting these differences of opinion out in the open is very 
helpful.

My view is that RDF is defined by the W3C RDF recommendation and that going 
beyond the inferences sanctioned here is no longer RDF.



>
> Best,
>
> Ruben

Petter
Received on Sunday, 13 April 2014 01:07:42 UTC

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