Re: [External] The Joy of NULLs (not)

It is strange. The problem is the way Wikidata presents blank nodes in tabular output.
I transformed the query into a CONSTRUCT one (https://w.wiki/74o) to see the blank
node in a standard RDF syntax. Also, I changed the "Accept" parameter in the request:

Accept: text/turtle, application/rdf+xml

The output is an RDF/XML file including:

<rdf:Description rdf:about="http://www.wikidata.org/entity/Q8747">
   <wdt:P19 rdf:nodeID="t517246030"/>
</rdf:Description>

The blank is presented as a blank node.

--
Daniel

 ---- On Tue, 13 Aug 2019 18:25:58 -0400 Hugh Glaser <hugh@glasers.org> wrote ----
 > Hmmm. Wikidata can be strange.
 > There is a lot of indirection around.
 > And the redesign pages can be very misleading.
 > I'm not sure I see any actual blank nodes there, or at least none getting exposed.
 > 
 > I see ?o gets a text value in the SPARQL output - of the form "tnnnnnnn".
 > Whereas for a person for whom more is known about the PoB, it is a URI of a place.
 > 
 > If I dig further (still using the SPARQL engine, the underlying real RDF may be different again!):
 > wd:Q8747           p:P19        ?o   .
 > gives
 > http://www.wikidata.org/entity/statement/Q8747-49454632-42cf-dca0-2ec4-47ece3472edf
 > which doesn't look like a blank node to me.
 > And in fact
 > wds:Q8747-49454632-42cf-dca0-2ec4-47ece3472edf ?p ?o .
 > leads you to "t517245985" via ps:P19
 > 
 > So, clearly the ISBLANK does something, so internally it is probably doing what you say, but that is not being exposed.
 > 
 > 
 > Cheers
 > 
 > > On 12 Aug 2019, at 15:05, Young,Jeff (OR) <jyoung@oclc.org> wrote:
 > > 
 > > Here’s an example showing blank nodes being used to declare the place of birth is unknown in Wikidata:
 > > 
 > > https://w.wiki/6$y
 > > 
 > > In the UI, it is rendered like this:
 > > 
 > > <image001.png>
 > > 
 > > Jeff
 > > 
 > > From: Daniel Hernandez <daniel@degu.cl>
 > > Date: Monday, August 12, 2019 at 9:42 AM
 > > To: "semantic-web@w3.org" <semantic-web@w3.org>
 > > Subject: [External] Re: The Joy of NULLs (not)
 > > Resent-From: <semantic-web@w3.org>
 > > Resent-Date: Monday, August 12, 2019 at 9:37 AM
 > > 
 > > As Enrico pointed, blank nodes can be used to represent unknown values.
 > > An example of this use is Wikidata. I don't know another example.
 > > 
 > > --
 > > Daniel
 > > 
 > > On Mon, 12 Aug 2019 07:36:41 +0000
 > > Franconi Enrico <franconi@inf.unibz.it> wrote:
 > > 
 > >> Mike, this could easily happen in an RDF world if you register a
 > >> vanity licence plate with anything starting with "_". Indeed, bnodes
 > >> would be the right way to represent unknown but existing plates. --e.
 > >> 
 > >> Il giorno 11 ago 2019, alle ore 23:10, Michael F Uschold
 > >> <uschold@gmail.com<mailto:uschold@gmail.com>> ha scritto:
 > >> 
 > >>> This is hilarious. It could never happen in an RDF world! No value,
 > >>> no triple.
 > >>> 
 > >>> He tried to prank the DMV. Then his vanity license plate backfired
 > >>> big time.
 > >>> https://mashable.com/article/dmv-vanity-license-plate-def-con-backfire/<http://flip.it/NIk7FD>
 > 
 > 
 > 
 > -- 
 > Hugh
 > 023 8061 5652
 > 
 > 
 >

Received on Tuesday, 13 August 2019 23:19:44 UTC