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Re: RDF-star use cases from Amazon Neptune

From: Peter F. Patel-Schneider <pfpschneider@gmail.com>
Date: Sun, 5 Dec 2021 15:47:41 -0500
Message-ID: <b865e392-2b29-b568-1c87-7489f4d85ea2@gmail.com>
To: Pierre-Antoine Champin <pierre-antoine.champin@ercim.eu>, public-rdf-star@w3.org
On 12/5/21 14:08, Pierre-Antoine Champin wrote:

> 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

Whether RDF is a logic or not is not relevant here.  The kind of logic that 
RDF employs is what matters.  It would be possible to create a logic for 
particular PG formalism that supports a semantics-based retrieval that retains 

>> 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?

Anyone can do anything with anything.  But SPARQL and SPARQL* are are 
official.  In my opinion, you can't analyze RDF without taking SPARQL into 
account.  My opinion is that most uses of RDF graphs go through SPARQL and 
thus the behaviour of SPARQL is much more important than the RDF semantics.  
So I would say that you can't consider RDF as strictly a non-counting logic.

This is just like the situation with relational data bases. Although 
relational data bases are strictly defined as sets of tuples, SQL uses 
multi-sets in some places.

>   pa
>> peter
>>> 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.
Received on Sunday, 5 December 2021 20:47:57 UTC

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