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Re: owl:sameAs/referential opacity Re: Can RDFstar be defined as only syntactic sugar on top of RDF (Re: weakness of embedded triples)

From: thomas lörtsch <tl@rat.io>
Date: Wed, 4 Nov 2020 00:08:53 +0100
Cc: Pierre-Antoine Champin <pierre-antoine.champin@ercim.eu>, public-rdf-star@w3.org
Message-Id: <51059C19-5DC2-491D-B5E0-D38F25839E0B@rat.io>
To: Miel Vander Sande <miel.vandersande@meemoo.be>

> On 2. Nov 2020, at 12:10, Miel Vander Sande <miel.vandersande@meemoo.be> wrote:
>> A simple solution would be that the applications throw an error or a warning if they encounter such triples, so going from TTL* to TTL will simply not happen in practice.
> Yes, that would be much better. But, as I wrote above, it amounts to acknowledge that these statement-encoding IRIs are, in fact, different from other IRIs. So they are a new type of nodes.
> Just to be clear: implementing that new type of nodes by piggybacking the internal IRI type is perfectly fine, as long as the implementation behaves in an interoperable way (i.e. it produces the correct Turtle*, and refrains from producing bogus Turtle). But specifying this interoperable behaviour is better achieved, I think, through an extended abstract syntax and semantics.
> I can only say +1 to this one. Let's not make the same mistake of leaving the semantics undefined. For the applications that are satisfied with RDF and SHACL, this might a less apparent problem. But there are others... And even if you decide to embed them in URIs, you'd still need to know what they mean. Honestly, this approach feels like an engineering hack to me, even without taking the contested theoretical/academic perspective on the matter.
> From working on Triple Pattern Fragments (which is related in a sense, because it defines a standard approach for encoding triples as URIs - tbh, I think we even made the reification argument in the first paper), I can also note that a maximum URI length is an issue in practice, which is a potential issue for anything Linked Data.

RDF* style << … >> triplets in examples are mostly shown with name spaced IRIs but when transmitting them over the wire they would need to be expanded and get just as long as proper IRIs. OTOH Holger linked to an example where they encode namespaced IRIs in other IRIs [0] but again, when transmitting over the wire of course they need to be expanded too. So it’s the same, except that the << … >> syntax is easier to read as it doesn’t require escaping.

That said I’d be really interested to know more about what the issues in practice are that you refer to. I’m sure you’ve seen a lot of IRIs when working on the laundromat.


> Cheers,
> Miel

[0] http://datashapes.org/reification.html#uriReification
Received on Tuesday, 3 November 2020 23:09:18 UTC

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