Hi Antoine,

On Thu, Oct 31, 2013 at 11:39 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?

If I understand the example correctly then yes I agree with you.
Qualifiers are there to qualify a statement. So for example to
indicate how a value was measured or from when to when a given
statement was true.

> 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?

Yes. The difference is that we explicitly state something to not be
there or to be there but we don't know more. Example: We know person X
had children but we don't know who they were.

> 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?

You can't but this is the best you can do I fear for the moment.


Cheers
Lydia

-- 
Lydia Pintscher - http://about.me/lydia.pintscher
Product Manager for Wikidata

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