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Re: "embedded predicate triples"

From: Pierre-Antoine Champin <pierre-antoine.champin@ercim.eu>
Date: Tue, 1 Dec 2020 12:01:47 +0100
To: james anderson <james@dydra.com>, "public-rdf-star@w3.org" <public-rdf-star@w3.org>
Message-ID: <285dc0f6-0d37-b9c5-5cdf-a8ad9f45a16b@ercim.eu>
James,

First, Singleton Properties (SP) use IRIs in the predicate position. 
They do not attempt to extend the RDF abstract syntax, and this is in 
fact one of their selling points (although, as pointed out by several 
authors, including Olaf [2], it has practical issues in many 
implementations).

Second, the very idea of SP is to have /single-use/ predicates, and 
consider them as identifying /the only triple/ in which they appear. By 
contrast, Jerven's suggestion would allow the same triple to be used in 
predicate position multiple times, but most importantly, to be used as 
the predicate of a triple whose subject and object are different from 
its own subject and object:

     :s2 << :s1 :p :o1 >> :o2.
     :s3 << :s1 :p :o1 >> :o3.

What on earth that would mean, I have absolutely no idea!

On 30/11/2020 12:12, james anderson wrote:
> the 27.11 discussion included a question about whether to permit “embedded triples” in the predicate role and why.
>
>      jerven: Question: why we don't have embedded triples in the property position?
>      ... we need to put in down somewhere in the proposal
>      Olaf: why would it be used for?
>      Is that use case somewhere in the use case list?
>      …
>      <pfps_> Indeed, if the meaning of RDF* is defined as just a vocabulary extension to RDF, and embedded triples are IRIs, then embedded triples should be allowed in predicate position in surface syntaxes. However, it looks as if embedded triples have to be blank nodes in this definition of RDF*, so they can't be in predicate position.
>      pchampin: We should stick for now with the restrictions
>      james_: Embedded quad is actually in one of the use case. I react on the the point of using embedded triples in the predicate
>      ... Describing a use case.
>      <pfps_> I don't see how embedded triples as predicates advances similarity to property graphs. I would need an example of a property graph to see how this might work.
>      Could james_ add that use case somewhere?
>      <Olaf> I don't understand
>
> this is not a new topic.
> the mechanism was described at length by nguyen along with an extended use case in [1] and rejected for rdf* by hartig in [2].
> ---
> [1] https://mor2.nlm.nih.gov/pubs/pdf/2014-www-vn.pdf
> [2] http://ceur-ws.org/Vol-1912/paper12.pdf
> ---
> james anderson | james@dydra.com | http://dydra.com
>
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Received on Tuesday, 1 December 2020 11:01:51 UTC

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