W3C home > Mailing lists > Public > public-rdf-wg@w3.org > September 2012

Re: "no-semantics" semantics

From: Antoine Zimmermann <antoine.zimmermann@emse.fr>
Date: Wed, 19 Sep 2012 01:47:59 +0200
Message-ID: <5059082F.4010506@emse.fr>
To: Pat Hayes <phayes@ihmc.us>
CC: Ivan Herman <ivan@w3.org>, RDF WG <public-rdf-wg@w3.org>
Le 18/09/2012 18:54, Pat Hayes a écrit :
>
> On Sep 18, 2012, at 5:55 AM, Ivan Herman wrote:
>
>>
>> On Sep 18, 2012, at 07:56 , Pat Hayes wrote:
>>
>>> <summary> The "RDF no-semantics" proposal does not make sense as written, and I do not think that it makes sense at all. If part of the current proposal depends upon the use of a semantics weaker than simple entailment, then it needs to be reconsidered. </summary>
>>>
>>
>> Short answer is: the current proposal does _not_ depend on that one.
>
> Then I suggest deleting mention of it from the wiki page describing the current proposal, because that is where I read it.

You've read it from 
http://www.w3.org/2011/rdf-wg/wiki/TF-Graphs/Dataset-semantics-2.0#RDF_no-semantics 
which is *not* where the current proposal is.

The current proposal is at 
http://www.w3.org/2011/rdf-wg/wiki/TF-Graphs/Minimal-dataset-semantics 
and it only says in the design issues that we have to consider the idea 
of a weaker semantics. Yes, it links to the document above, but it's 
only mentioned as a possible way to define it, if we ever want to do so. 
I am fine with removing the link if it really causes you stress.


AZ


>
> Pat
>
>>
>> Ivan
>>
>>
>>
>>> According to http://www.w3.org/2011/rdf-wg/wiki/TF-Graphs/Dataset-semantics-2.0#RDF_no-semantics, the no-semantics semantic condition is:
>>>
>>> I(G)=true if IR contains (an RDF graph isomorphic to) G.
>>>
>>> This does not really make any sense. Why would the presence of an object (of any kind) in the universe cause a graph to be true? This does not bear any relationship to the truth of the triples in the graph or the denotations of the URIs in the graph.  Notice that this would give the same entailments if any other part of the semantic conditions were required to contain G, for example if we were to say that i(G)=true if for some IRI R  in a triple in G, I(R)=G, or that I(G)=true if IP contains G. All that matters is that the 'truth' of G is defined so that the interpretation structure is required to contain G, and then entailment holds only for identity (or isomorphism) of the graph, trivially. But this 'tricks' the standard notion of truth to achieve the weaker entailment, and this trickery has the consequence that the usual notions of entailment are no longer strengthenings of this one.
>>>
>>> There is a standard way to relate a stronger notion of entailment to a weaker one, which is used extensively in the 2004 RDF semantics. One does it by restricting the class of possible interpretations. A entails B means that every interpretation which makes A true also makes B true. The more interpretations one allows in that "every", the weaker the entailement. So one gets RDF entailment from simple entailment by only allowing RDF interpretations (that is, simple interpretations which satisfy the RDF semantic conditions), and RDFS from RDF by only allowing RDFS interpretations, and so on. This is basic textbook stuff, model theory 101. But this does not work for this trick. A simple RDF interpretation is not a no-semantics interpretation with extra conditions added. The two kinds of interpretation bear essentially no relationship to one another: the "no-semantics" truth conditions are completely unrelated to the normal truth conditions, and the simple interpretation is not requ
ired to contain a graph in its universe.
>>>
>>> This trick also violates the basic intuitions underlying model theoretic semantics. The whole idea is to define the truth of complex expressions in terms of the semantic values of their subexpressions. In logic, for example, the truth of a sentence like (forall (x)(if (and (P x)(Q x)) (P x)))  is defined in terms of the denotations of (if (and (P x)(Q x)) (P x)), which in turn is defined in terms of the truth of  (and (P x)(Q x)) and of (P x), and so on. The "no-semantics" semantics does not do this.
>>>
>>> I am not willing to include this option as a part of a standard semantics document authored by me.
>>>
>>> Pat
>>>
>>>
>>> ------------------------------------------------------------
>>> IHMC                                     (850)434 8903 or (650)494 3973
>>> 40 South Alcaniz St.           (850)202 4416   office
>>> Pensacola                            (850)202 4440   fax
>>> FL 32502                              (850)291 0667   mobile
>>> phayesAT-SIGNihmc.us       http://www.ihmc.us/users/phayes
>>>
>>>
>>>
>>>
>>>
>>>
>>
>>
>> ----
>> Ivan Herman, W3C Semantic Web Activity Lead
>> Home: http://www.w3.org/People/Ivan/
>> mobile: +31-641044153
>> FOAF: http://www.ivan-herman.net/foaf.rdf
>>
>>
>>
>>
>>
>>
>>
>
> ------------------------------------------------------------
> IHMC                                     (850)434 8903 or (650)494 3973
> 40 South Alcaniz St.           (850)202 4416   office
> Pensacola                            (850)202 4440   fax
> FL 32502                              (850)291 0667   mobile
> phayesAT-SIGNihmc.us       http://www.ihmc.us/users/phayes
>
>
>
>
>
>
>


-- 
Antoine Zimmermann
ISCOD / LSTI - Institut Henri Fayol
École Nationale Supérieure des Mines de Saint-Étienne
158 cours Fauriel
42023 Saint-Étienne Cedex 2
France
Tél:+33(0)4 77 42 83 36
Fax:+33(0)4 77 42 66 66
http://zimmer.aprilfoolsreview.com/
Received on Tuesday, 18 September 2012 23:47:54 GMT

This archive was generated by hypermail 2.3.1 : Tuesday, 26 March 2013 16:25:51 GMT