RE: Attempting (vainly?) to change the subject was: Blank nodes must DIE! [ was Re: Blank nodes semantics - existential variables?]

Hi everyone,



[snip]



These different ways of interpreting Named Graphs (and more generally RDF Datasets) have been discussed ad nauseam in the RDF 1.1 Working Group. The group published a note about these options (https://www.w3.org/TR/rdf11-datasets/), that I authored. Although I authored it, it is not supposed to reflect my personal view on the topic. It is meant to reflect the state of the discussions within the working group, and the extent of the possibilities when it comes to interpreting Named Graphs and RDF Datasets.



               It's been a while since we tried plugging Notation3 in the mailing list :-) So here it goes: we illustrated<http://ceur-ws.org/Vol-2438/paper6.pdf> how one can represent different named graph semantics, based on the Antoine’s note (https://www.w3.org/TR/rdf11-datasets/), in Notation3. It allows the author to indicate the intended semantics of the named graph, via the predicate that connects the graph name to the named graph in an N3 triple. We provide a set of rules to implement four of these semantics - partitioning of triples, quoting of triples, isolated contexts, and online graphs (i.e., graph names denoting online graphs that are in some relation to the named graph). It’s neat because these rules allow any N3 system to easily support these four named graph semantics.





Regards,



William



-----Original Message-----
From: Antoine Zimmermann <antoine.zimmermann@emse.fr>
Sent: July-29-20 5:48 PM
To: Patrick J Hayes <phayes@ihmc.us>; Henry Story <henry.story@bblfish.net>
Cc: Semantic Web <semantic-web@w3.org>
Subject: Re: Attempting (vainly?) to change the subject was: Blank nodes must DIE! [ was Re: Blank nodes semantics - existential variables?]



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Le 29/07/2020 à 18:52, Patrick J Hayes a écrit :

>

>



[skip]



> Ahem. https://papers.ssrn.com/sol3/papers.cfm?abstract_id=3199260




Yes. It's important to differentiate between "there is nothing for X"

and "there is no *standard* for X". And also differentiate between "there is something for X" and "there is a *standard* for X".



In this case, there is a well documented formal semantics for Named Graphs, namely the one that Pat references. It also has the privilege to be the first published formal semantics of Named Graphs.



However, not only "Pat's Named Graph semantics" (I'll use this term to denote the semantics defined in Carroll et al.'s paper, that is, the one that Pat references) is not standard, but it also isn't the only one formal semantics for Named Graphs.



If a document D1 contains:



<x> {

   <Superman> <kissed> <LoisLane> .

   <Superman> owl:sameAs <ClarkKent> .

}



does it say the same thing as document D2:



<y> {

   <Superman> <kissed> <LoisLane> .

   <Superman> owl:sameAs <ClarkKent> .

}



? Or, does D1-union-D2 entails "<x> owl:sameAs <y>".



In Pat's Named Graph semantics, it does not. There are good reasons for this, which are explained in Carroll et al.'s paper. Yet, there are also good reasons (arguably) to use Named Graphs with the intent that D1 is equivalent to D2, or that it entails that D1-union-D2 entails "<x> owl:sameAs <y>".



Also, if D3 says:



<x> {

   <ClarkKent> <kissed> <LoisLane> .

}



then, in Pat's Named Graph semantics, it is not the case that D1 entails D3. Yet, there are good reasons (arguably) to use Named Graphs with the intent that D1 entails D3.



There are ways of defining a formal semantics for Named Graphs such that

D1 entails D2, or that D1 entails D3, or both.



These different ways of interpreting Named Graphs (and more generally RDF Datasets) have been discussed ad nauseam in the RDF 1.1 Working Group. The group published a note about these options (https://www.w3.org/TR/rdf11-datasets/), that I authored. Although I authored it, it is not supposed to reflect my personal view on the topic. It is meant to reflect the state of the discussions within the working group, and the extent of the possibilities when it comes to interpreting Named Graphs and RDF Datasets.



Now, personally, I have my preference. I would prefer that D1 entails D3, and I think that Pat's Named Graph semantics could be encoded using a different data structure similar to a "named graph literal".



For instance:



<alice> <likes> "<bob> {<Superman> <kissed> <LoisLane> . <Superman> owl:sameAs <ClarkKent>}"^^pat:NGSemantics .

<bob> {

   <Superman> <kissed> <LoisLane> .

   <Superman> owl:sameAs <ClarkKent>

}



would entail:



<bob> {

   <ClarkKent> <kissed> <LoisLane> .

}



but would not entail:



<alice> <likes> "<bob> {<ClarkKent> <kissed> <LoisLane> .}"^^pat:NGSemantics .



nor:



<alice> <likes> "<nick> {<Superman> <kissed> <LoisLane> . <Superman> owl:sameAs <ClarkKent>}"^^pat:NGSemantics .





Opinions may vary. (huho, I think I opened another big can of worms here...)

--

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 66 03

Fax:+33(0)4 77 42 66 66

http://zimmer.aprilfoolsreview.com/