Hello Antoine, just to add to what was already said:
a Qualifier in Wikidata is not a "statement about a statement". In RDF semantics, the pattern that we follow is not the reification of the triple and then to make triples with the reified triple as a subject, as per < http://www.w3.org/TR/rdf-mt/#ReifAndCont> but rather the pattern of n-ary relations per <http://www.w3.org/TR/swbp-n-aryRelations/> . The use cases very beautifully visualize how Wikidata maps to RDF: < http://www.w3.org/TR/swbp-n-aryRelations/#useCase1> This is also what Wikidata's mapping to RDF document explains and motivates: <https://meta.wikimedia.org/wiki/Wikidata/Development/RDF> I hope this helps, Denny On Oct 31, 2013 3:40 AM, "Antoine Zimmermann" <[email protected]> wrote: > Hello, > > > I have a few questions about how statement qualifiers should be used. > > > First, my understanding of qualifiers is that they define statements about > statements. So, if I have the statement: > > Q17(Japan) P6(head of government) Q132345(Shinzō Abe) > > with the qualifier: > > P39(office held) Q274948(Prime Minister of Japan) > > it means that the statement holds an office, right? > It seems to me that this is incorrect and that this qualifier should in > fact be a statement about Shinzō Abe. Can you confirm this? > > > > Second, concerning temporal qualifiers: what does it mean that the "start" > or "end" is "no value"? I can imagine two interpretations: > > 1. the statement is true forever (a person is a dead person from the > moment of their death till the end of the universe) > 2. (for end date) the statement is still true, we cannot predict when > it's going to end. > > For me, case number 2 should rather be marked as "unknown value" rather > than "no value". But again, what does "unknown value" means in comparison > to having no indicated value? > > > > Third, what if a statement is temporarily true (say, X held office from T1 > to T2) then becomes false and become true again (like X held same office > from T3 to T4 with T3 > T2)? The situation exists for Q35171(Grover > Cleveland) who has the following statement: > > Q35171 P39(position held) Q11696(President of the United States of > America) > > with qualifiers, and a second occurrence of the same statement with > different qualifiers. The wikidata user interface makes it clear that there > are two occurrences of the statement with different qualifiers, but how > does the wikidata data model allows me to distinguish between these two > occurrences? > > How do I know that: > > P580(start date) "March 4 1885" > > only applies to the first occurrence of the statement, while: > > P580(start date) "March 4 1893" > > only applies to the second occurrence of the statement? > I could have a heuristic that says if two "start date"s are given, then > assume that they are the starting points of two disjoint intervales. But > can I always guarantee this? > > > Best, > AZ > > -- > Antoine Zimmermann > ISCOD / LSTI - Institut Henri Fayol > École Nationale Supérieure des Mines de Saint-Étienne > 158 cours Fauriel > 42023 Saint-Étienne Cedex 2 > France > Tél:+33(0)4 77 42 66 03 > Fax:+33(0)4 77 42 66 66 > http://zimmer.aprilfoolsreview.com/ > > _______________________________________________ > Wikidata-l mailing list > [email protected] > https://lists.wikimedia.org/mailman/listinfo/wikidata-l >
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