Hi Antoine, all, I was also a bit puzzled by this. If you want more discussion I there is stuff on Gerard's blog [1,2]. After some patient explanations of the kind on this list, I think I understood what qualifiers are about.
Still I disagree with a part of what Markus said. Trying to understand claims as "statement about statements", as Antoine did, is not being concerned only about the informal meaning. It is a rather deep data modeling issue. In wikidata a qualifier can be about the object of a claim or about the claim itself (Markus' "meta" level), and there's no means to distinguish one from the other in the form of the data. In fact such "data structure" for qualifiers is much more dependent on an "informal reading" than thought: it fits really well how humans would enter and "read" the data, but less well what a machine would need to exploit it (as the construct is intrinsically ambiguous on whether it's an amendment to the truth conditions of a claim, or a n-ary relation). I'm not saying it's bad per se. The discussion made me understand better why it was designed so, and I can understand the advantages. Still I am not so sure it's really a winner in terms of interoperability with other systems. Best, Antoine http://ultimategerardm.blogspot.nl/2013/10/more-heady-stuff-about-wikidata-and.html http://ultimategerardm.blogspot.nl/2013/10/abdallah-ii-six-times-sultan-of-morocco.html
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" <antoine.zimmerm...@emse.fr <mailto:antoine.zimmerm...@emse.fr>> 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 <tel:%2B33%280%294%2077%2042%2066%2003> Fax:+33(0)4 77 42 66 66 <tel:%2B33%280%294%2077%2042%2066%2066> http://zimmer.__aprilfoolsreview.com/ <http://zimmer.aprilfoolsreview.com/> _________________________________________________ Wikidata-l mailing list Wikidata-l@lists.wikimedia.org <mailto:Wikidata-l@lists.wikimedia.org> https://lists.wikimedia.org/__mailman/listinfo/wikidata-l <https://lists.wikimedia.org/mailman/listinfo/wikidata-l>
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