Re: RDF-star use cases from Amazon Neptune

On 12/3/21 6:31 AM, Pierre-Antoine Champin wrote:
>
> Ora,
>
> thanks for these use-cases? Do you want to add an agenda item in 
> today's call for discussing them?
>
> Below are my 2¢ about this.
>
> > RDF semantics (...) stipulate that a triple <s, p, o> is unique 
> (...). In LPGs, however, no such restriction exists for edges.
>
> I think that presenting this feature of RDF as a "restriction" is 
> unfair, and misses the point. In my view, the impedance mismatch 
> between RDF and PGs is not due to some arbitrary restriction on the 
> RDF model. It is due to the fact that RDF is a logic, that can be 
> represented as a graph, while PG is a graph data model, without any 
> semantic commitment.
>
> An RDF triple (s p o) is a /statement/ before being an edge in a 
> graph. It states that the relation (denoted by) p holds between (the 
> things denoted by) s and o. That statement is either true or false; 
> therefore the triple is either in the RDF graph or it is not.
>
> Either Bob is married to Alice or not. Either there is a pipe between 
> M1 and M2 or there is none. If finer grained information is required 
> (which marriage? which pipe?), then additional nodes must be added (as 
> suggested by Jos in his answer, or in 
> https://w3c.github.io/rdf-star/cg-spec/2021-07-01.html#occurrences). 
> That is a feature of RDF, not a bug.
>
> > [ about the example with "double-nested" triples ]
> > This is of course a perfectly valid approach, but it does not match 
> the typical approach when using LPGs.
> > Note also that, while the example above captures the correct 
> semantics, it is awkward (...
>
> It might be awkward, but if it captures the correct semantics, then 
> maybe that's the way it should be represented in RDF ;-)
>
> More generally, I strongly believe that, because of the different 
> focuses of RDF vs. PG, we should not strive for a one-size-fit-all 
> mapping between the two. Different patterns in PGs convey different 
> semantics, therefore they should be mapped differently to RDF. This is 
> the line of work explored by Julian Bruyat in his PHD (which he also 
> presented at the SCG workshop [1]).
>
>   best
>
> [1] Bruyat et al.  "PREC: Semantic Translation of Property Graphs". 
> 1st Workshop on Squaring the Circle
> on Graphs (SCG2021), SEMANTiCS 2021. 
> https://mosaicrown.github.io/scg2021/#mu-schedule
>

Yes!

In my excitement I inadvertently truncated part of the original response :)


Kingsley

>
> On 02/12/2021 19:43, Lassila, Ora wrote:
>>
>> Folks,
>>
>> Attached is a document that outlines a couple of uses cases (variants 
>> of one modeling pattern ,really) we would like to submit for 
>> consideration by the upcoming RDF-star Working Group. I am submitting 
>> these now just in case this turns out to be relevant to how the 
>> charter gets written. Comments are welcome, and I am happy to discuss 
>> these use cases whenever.
>>
>> Regards,
>>
>> Ora
>>
>> -- 
>>
>> Dr. Ora Lassila
>>
>> Principal Graph Technologist, Amazon Neptune
>>
>> Amazon Web Services
>>
>> ora@amazon.com
>>

-- 
Regards,

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