This is very strange. Commons Media values are not supposed to be strings
in RDF – the documentation
<https://www.mediawiki.org/wiki/Wikibase/Indexing/RDF_Dump_Format#Commons_media>
confirms that they’re supposed to be Special:FilePath URIs, and for most
images, this is the case:
SELECT (STR(?image) AS ?str) (ISIRI(?image) AS ?isIri) WHERE {
wd:Q33231166 wdt:P18 ?image.
}
str
isIri
http://commons.wikimedia.org/wiki/Special:FilePath/GuentherZ%202010-02-27%2…
true
(The query service UI then rewrites that URL into a different one when
showing the result, sending you to the file description page instead of
directly to the file.)
To search for an image by its name, you can construct that URL in the query:
PREFIX commons: <http://commons.wikimedia.org/wiki/Special:FilePath/>
SELECT * WHERE {
hint:Query hint:optimizer "None".
BIND("1936-ChirkovAntonNikolaevich.jpg" AS ?fileName)
BIND(IRI(CONCAT(STR(commons:), ENCODE_FOR_URI(?fileName))) AS ?image)
?item wdt:P18 ?image.
}
I have no idea why your simple query, searching for the file name as a
string, actually works sometimes. I assume this must be a bug – I’ve
created T258782 <https://phabricator.wikimedia.org/T258782> to track it.
(Your first example, Q16718402 / 1936-ChirkovAntonNikolaevich.jpg, is now a
URL – Lydia edited the item to see if that resolved the issue, and after
the query service updater re-imported the item, the issue was gone.)
Hope this helps,
Lucas
Am Mo., 6. Juli 2020 um 18:34 Uhr schrieb Stephan Bösch-Plepelits <
skunk(a)xover.mud.at>gt;:
Hi!
I have a problem with a SPARQL query. Hopefully you can help me.
I'd like to get wikidata articles which use a specific image in the P18
property. I'm using this simple query:
SELECT ?item WHERE { ?item wdt:P18 "item.jpg". }
This works for some items, but not all.
Example 1:
SELECT ?item
WHERE { ?item wdt:P18 "1936-ChirkovAntonNikolaevich.jpg". }
-> returns "wd:Q16718402" (
https://www.wikidata.org/wiki/Q16718402)
Example 2:
SELECT ?item
WHERE { ?item wdt:P18 "GuentherZ 2010-02-27 0207 Wien10 Scheunenstrasse2
Bildstock.jpg". }
-> returns nothing, although it is used by
https://www.wikidata.org/wiki/Q33231166
This might be related to the following fact:
Example 1A:
SELECT ?item ?image
WHERE {
?item wdt:P18 ?image.
?item wdt:P214 "307433452".
}
-> the field "image" shows a string
"1936-ChirkovAntonNikolaevich.jpg"
Example 2A:
SELECT ?item ?foo
WHERE {
?item wdt:P18 ?image.
?item wdt:P2951 "86578".
}
-> the field "image" shows a link to
https://commons.wikimedia.org/wiki/File:GuentherZ%202010-02-27%200207%20Wie…
with the text "commons:GuentherZ 2010-02-27 0207 Wien10 Scheunenstrasse2
Bildstock.jpg"
(I also tried prefixing the query image name by 'commons:', like "?item
wdt:P18 "commons:image.jpg")
Please tell me if you have an idea how to solve this problem!
greetings,
Stephan
--
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