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Re: A case for a datatype for identifying RDF graphs

From: Maxime Lefrançois <maxime.lefrancois.86@gmail.com>
Date: Wed, 2 Jun 2021 10:44:03 +0200
Message-ID: <CALsPASVcE5m+bcwd79APZzrfYGmrF25T75We2LK31fb7d1t_ag@mail.gmail.com>
To: Pierre-Antoine Champin <pierre-antoine.champin@ercim.eu>
Cc: Antoine Zimmermann <antoine.zimmermann@emse.fr>, Semantic Web <semantic-web@w3.org>
Dear all,

May I draw your attention on LDScript, a Linked Data Script language
proposed by INRIA Sophia Antipolis
There are datatypes (and support thereof in the implementation) for:

@prefix st:  <http://ns.inria.fr/sparql-template/>  .
- RDF graphs - dt:graph
- triple - dt:triple
- SPARQL Query Solution Sequences - dt:mappings
- a SPARQL Query Solution  - dt:mapping

and many others for lists, json and xml documents, etc.
This is a pretty elegant solution IMHO.

see http://ns.inria.fr/sparql-extension/#datatype2

Best regards,
Maxime Lefrançois

Le mar. 1 juin 2021 à 17:56, Pierre-Antoine Champin <
pierre-antoine.champin@ercim.eu> a écrit :

> On 31/05/2021 09:55, Antoine Zimmermann wrote:
>
> >
> >> [...]
> >>
> >>>
> >>>
> >>> Long version:
> >>> ============
> >>>
> >>> Datatypes in RDF are used in order to refer to specific values that
> >>> can be processed adequately by computer systems, as opposed to
> >>> entities from the real world that can merely be referred to in such
> >>> systems without access to the real thing. For instance, if one wants
> >>> to refer to the integer "one", it is much better to use
> >>> "1"^^xsd:integer, that any system understands as the number "one" --
> >>> less than "2"^^xsd:integer and more than "0"^^xsd:integer -- rather
> >>> than using an identifier like
> >>> http://km.aifb.kit.edu/projects/numbers/n1 that may refer to a real
> >>> world entity to which the system has no understanding of.
> >>>
> >>> If one wants to refer to a *specific* instant in time, it is
> >>> preferable to identify it using xsd:dateTime rather than minting a
> >>> URI for the instant and relating it to its year, month, day, etc.
> >>>
> >>> If one wants to refer to a *specific* geometry on the Earth, it is
> >>> better to use a geo:wktLiteral rather than introducing a URI and a
> >>> vocabulary that would partially, and complexly define the geometry.
> >>
> >> Theoretically, literals are cleaner, granted.
> >
> > Theory should tell you what happens in practice.
> I would rather say "what CAN happen" in practice. See more below
> > If practice does not match theory, then you have a bad theory.
> Agreed, of course.
> > "In theory, if you use this amount of fuel with a rocket of this
> > shape, launch it with this angle at this time of the year from this
> > place, you should be able to go to the moon. But in practice, everyone
> > knows that it is impossible to go to the moon."
> >
> >>
> >> In practice, I see this more as a trade-off, and the best answer
> >> depends on your use-cases. For dates, it is sometimes useful to be
> >> able to access their "parts" by simply following an arc.
> >
> > I don't agree that it is simpler to locate a node that stands for a
> > date, find the relevant arcs and get a value for a component of a
> > date. It's much easier to have a node that's self-described as a
> > xsd:date or xsd:dateTime and use standard datetime-functions to
> > extract components.
> >
> > The "follow the arc" solution requires graph matching, which is costly.
> >
> > Nodes and arcs to describe a date are useful if you are uncertain
> > about some components of a date. For instance, birthdates of
> > historical figures of the middle ages are often unknown but
> > identifiable within a certain range.
>
> Note that I didn't write "simpler" or "cheaper", I wrote "sometimes
> useful" ;-) So we seem to agree after all.
>
> Note also that as soon as *some* of your dates are incomplete, dealing
> with two different kinds of representations (literals for complete
> dates, blank nodes with properties for incomplete dates) may become
> complicated, and justify to use the 2nd kind even for complete dates.
>
> But we are getting carried away from the original topic.
>
> >
> >> (this is where N3 shines, by the way, but that's another topic)
> >>
> >>>
> >>> If one wants to refer to a specific RDF graph, that could be
> >>> processed based on the datatype that identifies it as such, it would
> >>> be more efficient and robust to use a literal rather than a URI that
> >>> supposedly identifies it.
> >>>
> >>> I see many discussions that attempts to address the problem of
> >>> identifying specific RDF graphs (or specific triples) using
> >>> extensions of RDF, such as named graphs, or RDF-star, when all we
> >>> need is a datatype that is fully inside the scope of RDF syntax and
> >>> semantics.
> >>
> >> Again, theoretically you are right; however... the specifics of that
> >> datatype would still have to be built into RDF implementations...
> >
> > Again, there is no theory vs practice. You take the specification of a
> > graph-literal datatype, implement it within your RDF API, and then you
> > have a way to refer to RDF graphs, *in practice*.
>
> In practice, no such implementation exists (AFAIK). So this is mere
> theory for the moment.
>
> By saying that, I do not mean to dismiss the proposal as being
> unrealistic or uninteresting -- again, I *like* the proposal, and I do
> think it is worth implementing it!
>
> But in the meantime, I expect people to (ab)use other tools that
> immediately available (such as named graphs), even if not standard (such
> as RDF*), to solve the kind of problems that graph literals are meant to
> solve.
>
> > Such practical implementation is conforming to the RDF specification
> > as is.
> >
> >
> >> RDF datasets, on the other hand, are already largely implemented.
> >> (and so is RDF-star, to some extent :->)
> >
> > RDF datasets should not be seen as a conflicting alternative to the
> > graph-literal datatype. They are compatible and complementary.
>
> I agree. I hope my response above clarifies what I meant here.
>
>    pa
>
> >
> >
> > --AZ
> >
> >>> [...]
> >
>
>
Received on Wednesday, 2 June 2021 08:45:13 UTC

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