# try with SELECT ?s { ?s wdt:P31 wd:Q5185279 } LIMIT 20
PREFIX xsd: <http://www.w3.org/2001/XMLSchema#>
PREFIX prov: <http://www.w3.org/ns/prov#>
PREFIX wikibase: <http://wikiba.se/ontology#>
PREFIX wd: <http://www.wikidata.org/entity/>
PREFIX wdt: <http://www.wikidata.org/prop/direct/>
PREFIX p: <http://www.wikidata.org/prop/>
PREFIX ps: <http://www.wikidata.org/prop/statement/>
PREFIX pq: <http://www.wikidata.org/prop/statement/qualifier/>
PREFIX pr: <http://www.wikidata.org/prop/reference/>
start = @<#poem>
# A good poem item should have one or more authors (even if linked to Anonymous),
# and exactly one publication date (means when it was first published or released).
<#poem> EXTRA p:P50 p:P31 p:P577 {
wdt:P31 [wd:Q5185279]; # instance of poem
p:P50 @<#author>+;
p:P577 @<#publicationDate>?; # made optional for more results (get's us going)
}
# An author statement should point to a Wikidata item or “unknown value”,
# and optionally has references (good ones or other ones).
<#author> EXTRA prov:wasDerivedFrom {
wikibase:rank [wikibase:NormalRank wikibase:PreferredRank];
# (ps:P21 [wd:~] | ps:P21 BNode ); -- disabled to get some results
prov:wasDerivedFrom @<#reference>*;
}
# A publication date statement should have a dateTime value or “unknown value”
# and at least one good reference (plus any other references).
<#publicationDate> EXTRA prov:wasDerivedFrom {
a [wikibase:BestRank];
# (ps:P569 xsd:dateTime | ps:P569 BNode); -- disabled to get some results
prov:wasDerivedFrom @<#reference>+;
}
# A good reference should have been “stated in” some work (optionally with a “retrieved” date),
# or have a reference URL with a “retrieved” date (not optional here),
# or both.
<#reference> {
}
<#reference999> {
pr:P248 [wd:~]; # stated in
pr:P813 xsd:dateTime?; # retrieved
|
pr:P854 IRI; # reference URL
pr:P813 xsd:dateTime; # retrieved
|
pr:P248 [wd:~]; # stated in
pr:P854 IRI; # reference URL
pr:P813 xsd:dateTime; # retrieved
}
