You're not really supposed to use a named blank node as if it had a specific meaning.

rdf:nil represents the empty list and is a good stand-in for "no value" situations.

On Fri, Feb 26, 2016 at 7:32 AM, James Heald <j.heald@ucl.ac.uk> wrote:
These are used as placeholders for the meta-values "unknown value" and "no value" aren't they ?


On 26/02/2016 12:27, Markus Kroetzsch wrote:
Hi Stas, hi all,

I just noted that BlazeGraph seems to contain a few erroneous triples.
The following query, for example, returns a blank node "t7978245":

SELECT ?superClass WHERE {
   <http://www.wikidata.org/entity/Q595133> p:P279/ps:P279 ?superClass
}

https://query.wikidata.org/#SELECT%20%3FsuperClass%20WHERE%20{%0A%20%20%3Chttp%3A%2F%2Fwww.wikidata.org%2Fentity%2FQ595133%3E%20p%3AP279%2Fps%3AP279%20%3FsuperClass%0A}


I stumbled upon six cases like this (for P279): Q595133 (shown above),
Q1691488, Q11259005, Q297106, Q1293664, and Q539558. This would be less
than 0.001% of the 623,963 P279 statements, but it's still enough to
have application code trip over the unexpected return format ;-).

Best

Markus



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