Hi!

On 10/3/17 4:49 PM, Marco Neumann wrote:
> thank you Lucas and Stas, this works for me.
>
> so it would be fair to say that p:P39 by-passes the semantics of
> wdt:P39 with ranking*. for my own understanding why is a wdt property
> called a direct property**?

Because wdt: links directly to value, while p: links to a statement
(where ps: links to the value). But that's not the only property of wdt:
- another property that it links to "truthy" (current, best, etc.) value
- one that has best rank in this property (hence the "t" letter). This
may be what you want or not, depending on general semantics and your
particular case. For many properties, ranks do not play significant
role, since these properties do not change with time and do not have
temporally limited statements. So for these, using wdt: is always ok.
For some, like positions, offices, relationships between humans, etc.
the values can have temporal limits and if you want best/current one,
you use wdt:, otherwise you use p:/ps:. If you still want to account for
rank using p:/ps:, there are rank triples and wikibase:BestRank class
(see
https://www.mediawiki.org/wiki/Wikibase/Indexing/RDF_Dump_Format#Statement_representation).


--
Stas Malyshev
smalyshev@wikimedia.org

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