Re: RDF-star use cases from Amazon Neptune

On 05/12/2021 02:46, Peter F. Patel-Schneider wrote:
> Although RDF is in some sense a logic, this is not really relevant to 
> the discussion here.
I still beg to differ. See below
>
> There is no requirement that a logic be based on sets (or set-like 
> graphs) instead of multi-sets (or multi-set-like graphs).

That's right, but RDF as a logic is.

Rephrasing my point below: this "restriction" of RDF is not an arbitrary 
choice that could be easily revised, because it is linked to the 
underlying semantics of RDF. Furthermore, since PGs do not have an 
underlying semantics, the same construct can be used with a different 
meaning in different contexts (e.g. some edges are considered as 
automatically asserted, while other edges are only asserted 
conditionally to some properties). So even if we changed the RDF 
abstract syntax to better align with the PG data model, I expect that 
there would still be common PG patterns that would not map well to the 
new RDF's semantics.

> SPARQL and SPARQL* do not use the logic of RDF.  They have no more 
> semantic commitment than retrieval from property graphs.

Granted. People can use RDF while totally ignoring its semantics, and 
still query it with SPARQL and maybe get something useful from it. But 
would that still be RDF? If they published this data on the web, would 
it be desirable that they advertise it as RDF?

   pa

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> peter
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>> On 12/3/21 6:31 AM, Pierre-Antoine Champin wrote:
>>> 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.
>