Re: Blank nodes must DIE! [ was Re: Blank nodes semantics - existential variables?]

I really appreciate all the replies, thank you.

Why not use the literal?
>

I'm at the edge of my RDF knowledge here, but say I want to define my own
composite value type, like Circle for example?

The way I'd imagine doing it is:

    Circle
    type: rdfs:Datatype

    _:circle1
    type: Circle
    center: _:coordinate1
    radius: 10

Anthony


On Tue, Jul 7, 2020 at 4:48 PM Cox, Simon (L&W, Clayton) <Simon.Cox@csiro.au>
wrote:

> In this specific case it could be rdf:type time:DateTimeDescription from
> OWL-Time.
>
> See https://www.w3.org/TR/owl-time/#time-position
>
>
>
> *From:* Patrick J Hayes <phayes@ihmc.us>
> *Sent:* Wednesday, 8 July, 2020 09:20
> *To:* Anthony Moretti <anthony.moretti@gmail.com>
> *Cc:* thomas lörtsch <tl@rat.io>; Dieter Fensel <dieter.fensel@sti2.at>;
> Hugh Glaser <hugh@glasers.org>; Semantic Web <semantic-web@w3.org>;
> MindLab <mindlab@lists.sti2.at>
> *Subject:* Re: Blank nodes must DIE! [ was Re: Blank nodes semantics -
> existential variables?]
>
>
>
>
>
>
>
> On Jul 7, 2020, at 5:54 PM, Anthony Moretti <anthony.moretti@gmail.com>
> wrote:
>
>
>
> Hmm, not to me they don’t. Blank nodes are basically anonymous variables.
> LIterals are names with a /fixed/ denotation, a meaning fixed by external
> constraints, like a proper name.
>
>
>
> And what about just for the subset of blank nodes whose type is an
> rdfs:Datatype, such as the example?
>
>
>
> Well, I would be inclined to just always use literals as literals, rather
> than as codes for a subgraph with a bnode. But if that were in the graph
> then I would say, treat the bnode like any other bnode. Nothing will break
> if you do.
>
>
>
> Why put a blank node in there?
>
>
>
> Yeah I agree, there's absolutely no need for an identifier, its properties
> are sufficient, and any processing should ignore the ID. I put it in for
> completeness though because it's the only way I know to say something like flight123
> hasArrivalTime _:dateTime1 without using the dateTime literal.
>
>
>
> I must be missing something in this conversation. Why not use the literal?
> That is what literals are for, after all.
>
>
>
> Pat
>
>
>
>
>
> Anthony
>
>
>
>
>
> On Tue, Jul 7, 2020 at 2:47 PM Patrick J Hayes <phayes@ihmc.us> wrote:
>
>
>
>
>
> On Jul 7, 2020, at 1:47 PM, Anthony Moretti <anthony.moretti@gmail.com>
> wrote:
>
>
>
> Very interesting reading, Pat. Pushing my knowledge a bit here, but should
> literals also become a subset of the graffiti of S, and not just blank
> nodes? (Slide 21
> <https://image.slidesharecdn.com/iswc2009pathayes-091028162812-phpapp01/95/blogic-iswc-2009-invited-talk-21-728.jpg?cb=1256747359>
> )
>
>
>
> Literals seem like syntactic sugar for blank nodes,
>
>
>
> Hmm, not to me they don’t. Blank nodes are basically anonymous variables.
> LIterals are names with a /fixed/ denotation, a meaning fixed by external
> constraints, like a proper name.
>
>
>
> so whatever applies to blank nodes seems like it should apply to literals
> too, for example:
>
>
>     "2020-01-01T00:00:00"^^xsd:dateTime
>
>
>
> The literal seems to only exist as a convenient way of writing:
>
>
>
>     _:dateTime1
>
>     type: xsd:dateTime
>
>     year: 2020
>
>     month: 01
>
>     day: 01
>
>     hour: 00
>
>     minute: 00
>
>     second: 00
>
>
>
> Why put a blank node in there? This is like saying “Something which is
> midnight on 1 january 2020” instead of “midnight on 1 january 2020”. I
> mean, you CAN always do this, but the longer form doesn’t gain you anything
> and since the description uniquely specifies what you are talking about, it
> doesn’t add anything new.
>
>
>
> Pat
>
>
>
>
>
> In Swift, you write code the normal way using Int and Float etc., but
> behind the scenes and hidden from users they're actually implemented as
> structures. So one could alternatively argue that literals must die
> (joking).
>
>
>
> Regards
>
> Anthony
>
>
>
>
>
> On Tue, Jul 7, 2020 at 2:41 AM thomas lörtsch <tl@rat.io> wrote:
>
>
>
> > On 7. Jul 2020, at 05:22, Patrick J Hayes <phayes@ihmc.us> wrote:
> >
> >
> >
> >> On Jul 6, 2020, at 3:44 PM, Dieter Fensel <dieter.fensel@sti2.at>
> wrote:
> >>
> >> Hi Hugh,
> >>
> >> yes I agree and thanks for the pointer which we will check carefully.
> Actually we could enfore some strong recommendations for future information
> items in the distributed sources but why should you waste your time when
> you can hid the issue behind same-as. Full agreement! My point was more:
> >>
> >> - we started to define a framework for finding "nice" URIs for
> touristic information coming from heterogeneous sources (events,
> accommodations, trails, PoI, restaurants, etc.). Close to the end of our
> exercise we realized that what we are actually doing is just a special case
> of duplication detection, entity resolution, etc., etc., etc., etc. We even
> started to wonder whether we really need these "nice" URIs or better just
> describe entities by their properties and use a strange blank note as an
> "identifier". The first time after more than 20 years (also through the
> help of Andreas who was eating my ears on this issue) I started to
> understand why some nurts are so dedicated about them.
> >
> > Nurts? Did you mean nurds, or is this a new word? I hope so, because it
> is a wonderful word, with echoes of nut, nurd, hurt and snort.
> Congratulations.
> >
> >> In the end what is better, a random number as identifier or the magic
> of an existential variable.
> >
> > Or Q<number> which Denny likes to use in Wikidata.
> >
> >>
> >> - Especially the comment of Dan on global scale skolems made me a bit
> worrying, too. We seem to try very hard to turn the duplication detection,
> entity resolution, etc., etc., etc. problem to its full potential and we
> somehow would seem to try to give names to formulae and sets of entities.
> Now I know that for FOL even Aidans' super power approach would not work
> (or say semi-work). For a simple logic as RDF it may; but still? [1]
> >>
> >> So summarizing blank notes in a nutshell: I hope very much that they
> are not just another rdf:typo. What I mean: Would it not be nice to have
> RDF as a simple data model and RDFS etc. as a first simple logical
> languages on top of them? Maybe much too late and also wrong, however, can
> we ignore the rumour on the street that steadily (!) pops up quite visible
> on this slightly magic stuff.
> >
> > Let me recommend (re?) reading my ISWC 2009 invited talk. If we provide
> (1) a clear way to indicate bnode scopes and (2) negation to RDF, it is
> already FOL. We can do both with one single, simple extension to the syntax
> (and a small modification ot the semantics, routine stuff). Then we don't
> need all these new languages in 100 different syntaxes all “on top” of RDF.
> This leapfrogs OWL expressivity, and one could always provide
> OWL-Manchester-like macros, or some other “intuitive” notation (maybe
> defined using SHACL?) to keep the poor users from being burnt to death (or
> is turned into salt?) by the sight of actual logic.
> >
> > Best
> >
> > Pat
> >
> > https://www.slideshare.net/PatHayes/blogic-iswc-2009-invited-talk.
> especially starting at slide 15
>
> Also available on videolectures.net:
> http://videolectures.net/iswc09_hayes_blogic/
> 7013 views already!
>
> >>
> >> Greetings,
> >>
> >> Dieter
> >>
> >> [1] Btw, I would not mind if I get harshly corrected as I talk
> alongside the boundaries of my knowledge.
> >>
> >> On 05.07.2020 23:16, Hugh Glaser wrote:
> >>> Hi Dieter.
> >>>
> >>> That sounds very like the sort of thing that we use sameAs services
> for.
> >>> In particular, if you don't bring the data into one store, you can't
> do "normalisation" without writing stuff back into multiple sources stores.
> >>> I guess you are bringing the data into one store, so you can use
> normative URIs.
> >>>
> >>> If not, a while ago we spent a while building an Open Source sameAs
> Lite service (including a lot of benchmarks to optimise the table
> structure.)
> >>> It's at https://github.com/seme4/sameas-lite
> >>> The Github structure seems to have degraded a little since then but
> I'm sure would be serviceable if you found it useful - we'd be happy to
> help.
> >>>
> >>> Even if you are managing URIs, you might find this way of managing
> them has benefits.
> >>>
> >>> Best
> >>> Hugh
> >>>
> >>>> On 5 Jul 2020, at 15:37, Dieter Fensel <dieter.fensel@sti2.at> wrote:
> >>>>
> >>>> Thanks for the pointer. We may use this work in a project where we
> try to normalize URIs for a German Tourstic Knowledge Graph. There may be
> different URIs from different sources and we normalise these and give them
> a normative URl from established data sources on the web if possible (sorry
> in German [1]). Otherwise we some randomly generated IDs. Your work also
> may have relations to ID generation like studies in the OCCAM project or
> general in the IoT field (as Dan indirectly points out).
> >>>>
> >>>> [1]
> >>>>
> >>> ...
> >>>> --
> >>>> Dieter Fensel
> >>>> Chair STI Innsbruck
> >>>> University of Innsbruck, Austria
> >>>> www.sti-innsbruck.at/
> >>>> tel +43-664 3964684
> >>>>
> >>>>
> >> --
> >> Dieter Fensel
> >> Chair STI Innsbruck
> >> University of Innsbruck, Austria
> >> www.sti-innsbruck.at/
> >> tel +43-664 3964684
>
>
>
>
>