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Re: Why nested triples?

From: Miel Vander Sande <miel.vandersande@meemoo.be>
Date: Fri, 19 Feb 2021 18:09:08 +0100
Message-ID: <CAHeRLWsONzmRrZ+3HVisssB+jKQh4HptxhACufeW_-T8OQ=1Zw@mail.gmail.com>
To: thomas lörtsch <tl@rat.io>
Cc: Andy Seaborne <andy@apache.org>, public-rdf-star@w3.org
The use cases are not so future. In cultural heritage and GLAM sector, the
need to express uncertainty and claims goes deep.

An example from possible metadata on the graphic novel 'From Hell':
:AlanMoore :used << :StephenKnight :suggested <<:WilliamGull :operatedOn
:AnnieCrook>> >> .

If you don't want to use nesting, then don't? I don't think it will be used
much in practice, but I don't want to get into the situation where we have
to invent stange constructs because we were being too pragmatic. Clearly,
Jena and Ontotext already managed to implement the syntax, so it can't be
that much of a showstopper.

Op vr 19 feb. 2021 om 17:00 schreef thomas lörtsch <tl@rat.io>:

>
>
> > On 19. Feb 2021, at 15:16, Andy Seaborne <andy@apache.org> wrote:
> >
> > It does not have to be as either/or.
> >
> > An application/sub-system can mask nested embedded triples from a
> general parser.
> >
> > Current use cases are not defining the limit of uses in the future.
> >
> > "largely unnecessary" is to me a reason to include them, because we
> don't know the future use cases and patterns
>
> This seems to me to be as arbitrary an argument as it can possibly get.
>
> Thomas
>
>
>
> > - as per Olaf's example.
> >
> >    Andy
> >
> > On 18/02/2021 22:10, Holger Knublauch wrote:
> >> My input:
> >> I think nested triples should not be allowed. They are largely
> unnecessary, will cause extra work and put limitations on the design
> choices.
> >> As an implementer I can say that we don't support nested triples and do
> not want to (have to) support them.
> >> Even in the case that RDF-star introduces a new term type, it would be
> easy to exclude certain combinations, such as that triple terms cannot be
> subject, predicate or object of another triple term. Similar restrictions
> (thankfully) already exist in normal, non-generalized RDF. Such
> restrictions mean that algorithms that actually use/display/consume RDF
> have fewer cases to cover, and this will help the adoption of RDF-star in
> industry.
> >> There are in my experience significant downstream costs to users even
> if it sounds nice, consistent and symmetric from a spec point of view and
> for those who write low-level algorithms, parsers etc.
> >> Holger
> >> On 2021-02-19 12:02 am, Antoine Zimmermann wrote:
> >>> The RDF-star syntax allows for arbitrary nesting of triples like so:
> >>>
> >>> << :s :p << << :a :b :c >> :y :z >> a :nesting .
> >>>
> >>> Why is it so, why is it useful/needed?
> >>> There are no examples of nested triples. There are no justifications
> in the spec for allowing this. As far as I know, there are no examples in
> the past documents that defined RDF*. I did not see any use cases discussed
> for them.
> >>>
> >>> However, I have seen discussions that may serve as counter arguments:
> when asked why embedded triples are limited to single triples rather than
> sets of triples, it has been answered that RDF* is used to model
> property-graph-like annotations that only concern one edge at a time. In
> this case, nested triples should not be allowed, using the same arguments
> (as far as I know, it is not possible to nest edge-annotations in property
> graph systems).
> >>>
> >>> Nesting makes parsers more complicated, makes it more difficult to
> define the semantics of the data model as well as of the query language.
> >>>
> >>> If some use cases justify nested triples, then why not use cases
> justify embedded sets of triples?
> >>>
> >>>
> >>> Also, a question to implementers: do you support nested embedded
> triples?
> >
>
>
>
Received on Friday, 19 February 2021 17:09:48 UTC

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