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

 

Hi all, 

Thank you for this interesting discussion. 

Talking about claims, maybe we have to consider the idea of ​​trust
(from the point of view of the data consumer) in addition to the idea of
​​truth. 

If someone trust two sources, in her query she may want to merge the
graphs asserted by both sources. It is her choice. 

Maybe some of these issues belong to the application layer. 

Best regards, Laufer 

Em 30/07/2020 19:03, Henry Story escreveu: 

> Thanks for a lot of these great links and comments.
> 
> One thing that occurs to me is that there is something very similar going on with named
> graphs and the way intutionistic logicians look at elements of a type. They think of types
> as propositions, and elements of a type as warrants for that proposition.
> 
> In a way named graphs allow us to speak about what warrants an assertion.
> A conclusion I come to may be the consequence of merging a number of graphs,
> which individually or as group may warrant a claim. The name of the graph is
> such a claim.
> 
> Btw. There are some very clear and recent lectures by Peer Martin-Löf that 
> take speech acts as fundamental to logic and emphasize the so put the normative
> at the center of logic. I have a whole thread on Twitter with pointers 
> to papers (some of which are unpublished but for which I managed to get 
> copies by asking Ansten Klev)
> 
> https://twitter.com/bblfish/status/1241425579611750400 [1]
> 
> Now RDF is first order logic and intuitionistic logic is a constructive logic,
> identified in Category Theory as a Topos. Weirdly enough there
> is something like a co-intutionistic logic that turns out to be the logic 
> of falsification, which Popper actually knew about and is it seems 
> the basis of his work.
> https://link.springer.com/article/10.1007/s11225-005-8474-7 [2]
> 
> One can thus think as a debate as one between someone constructing a position
> and someone falsifying it. The result of zipping those two up gives us first
> order logic, where RDF is located.
> 
> On 30 Jul 2020, at 02:29, Patrick J Hayes <phayes@ihmc.us> wrote:
> 
> You did open up an old can, Antoine. I will try not to shake it too hard, just some points for clarification.
> 
> On Jul 29, 2020, at 3:48 PM, Antoine Zimmermann <antoine.zimmermann@emse.fr> wrote:
> 
> Le 29/07/2020 à 18:52, Patrick J Hayes a écrit :
> 
> [skip]
> 
> Ahem. https://papers.ssrn.com/sol3/papers.cfm?abstract_id=3199260 [3] 
> 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> .
> }
> 
> ?

Of course they say the same thing. They are equivalent graphs, in RDF
and in our semantics. But that doesn't make them identical. 

> 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>".

I havn't seen any good reasons for that. If I publish <x> in China on
Wednesday and you publish <y> in Russia on Saturday, and <x> = <y> so
they are the same thing, which of us published it, and when? 

> Also, if D3 says:
> 
> <x> {
> <ClarkKent> <kissed> <LoisLane> .
> }
> 
> then, in Pat's Named Graph semantics, it is not the case that D1 entails D3.

Because they have the same name, but are different graphs. That is
impossible if graph names are rigid names: it is like having xsd:integer
have its usual meaning in one place but mean xsd:real somewhere else. If
D3 hadn't stolen and misused the name, and called their graph <z>
instead of <x>, then the entailment would be fine. 

> 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/ [4]), 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.

The document you wrote is a great survey, but I would remark that it is
oriented towards datasets, where the graph name and the graph it names
are syntactically very close, whereas our paper was thinking of names
being used to refer to graphs out on the open Web. 

> 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".

Could this handle the kind of application we focussed on, with warrants
on the open web? It is a lot more use than using RDF to talk about
Superman :-)

Pat

> 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/ [5]

Henry Story

https://co-operating.systems [6]
WhatsApp, Signal, Tel: +33 6 38 32 69 84‬ 
Twitter: @bblfish

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劳费尔

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Links:
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[1] https://twitter.com/bblfish/status/1241425579611750400
[2] https://link.springer.com/article/10.1007/s11225-005-8474-7
[3] https://papers.ssrn.com/sol3/papers.cfm?abstract_id=3199260
[4] https://www.w3.org/TR/rdf11-datasets/
[5] http://zimmer.aprilfoolsreview.com/
[6] https://co-operating.systems