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%7B%0A%20%20%3C... https://query.wikidata.org/#SELECT%20%3FsuperClass%20WHERE%20%7B%0A%20%20%3Chttp%3A%2F%2Fwww.wikidata.org%2Fentity%2FQ595133%3E%20p%3AP279%2Fps%3AP279%20%3FsuperClass%0A%7D
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
Wikidata mailing list Wikidata@lists.wikimedia.org https://lists.wikimedia.org/mailman/listinfo/wikidata