Really impressive! On Fri, Mar 20, 2015 at 6:09 PM Markus Kroetzsch < markus.kroetz...@tu-dresden.de> wrote:
> Dear all, > > Thanks to the people at the Center of Semantic Web Research in Chile > [1], we have a very first public SPARQL endpoint for Wikidata running. > This is very preliminary, so do not rely on it in applications and > expect things to fail, but you may still enjoy some things. > > http://milenio.dcc.uchile.cl/sparql > > The endpoint has all the data from our current RDF exports in one big > database [2]. Below this email are some example queries to get you > started (this is a bit of a learning-by-doing crash course in SPARQL > too, but you may want to consult a tutorial if you don't know it ;-). > > There are some known bugs in the RDF that we will hopefully fix soon > [3]. Also, the service uses a dump that is already a few weeks old now. > We are more interested in testing functions right now before going > production. Also, this is a raw API interface, not a proposal for a nice > UI. > > Feedback (and other interesting queries) are welcome :-) > > Cheers, > > Markus > > > [1] http://ciws.cl/ -- a joint team from University of Chile and > Pontificia Universidad Catolica de Chile > [2] http://tools.wmflabs.org/wikidata-exports/rdf/ > [3] > https://github.com/Wikidata/Wikidata-Toolkit/issues?q=is% > 3Aopen+is%3Aissue+label%3A%22RDF+export%22 > > > ==Lighthouses (Q39715) with their English label (LIMIT 100 for demo)== > > PREFIX : <http://www.wikidata.org/entity/> > SELECT * > WHERE { > ?lighthouse a :Q39715 . > ?lighthouse rdfs:label ?label FILTER(LANG(?label) = "en") > } LIMIT 100 > > (Just paste the query into the box at http://milenio.dcc.uchile.cl/sparql) > > The actual query condition is in the WHERE {...} part. Things starting > with ? are variables. Basic conditions take the form of triples: > "subject property value". For example, "?lighthouse a :Q39715" looks for > things that are a lighthouse ("a" is short for "rdf:type" which we use > to encode P31 statements without qualifiers). The dot "." is used as a > separator between triples. > > Note that the label output is a bit cumbersome because you want to > filter by language (without the FILTER you get all labels in all > languages). A future UI would better fetch the labels after the query, > similar to WDQ, to get smaller & faster queries. > > > ==People born in the same place that they died in== > > PREFIX : <http://www.wikidata.org/entity/> > SELECT ?person ?personname ?placename > WHERE { > ?person a :Q5 . > ?person :P19c ?place . > ?person :P20c ?place . > ?person rdfs:label ?personname FILTER(LANG(?personname) = "en") . > ?place rdfs:label ?placename FILTER(LANG(?placename) = "en") > } LIMIT 100 > > Here we use a few actual Wikidata properties. Properties in their simple > form (Entity->Value) use ids with a "c" in the end, like :P19c here. > Only qualifier-free statements will be available in this form right now. > Note that we use the variable ?place in two places as a value. This is > how we query for things that have the same place in both cases. > > > ==People who have Wikipedia (Q52) accounts== > > PREFIX : <http://www.wikidata.org/entity/> > SELECT ?person ?personname ?username > WHERE { > ?person :P553s ?statement . > ?statement :P553v :Q52 . > ?statement :P554q ?username . > ?person rdfs:label ?personname FILTER(LANG(?personname) = "en") . > } LIMIT 100 > > This query needs to access qualifiers of a statement for "website > account on" (P553). To do this in RDF (and SPARQL), we access the > statement object instead of using simple property :P553c (which would > only give us the value). The statement is found through an "...s" > property; its value is found through a "...v" property; its qualifiers > are found through "...q" properties. Check out the graph in our paper to > get the picture > (http://korrekt.org/page/Introducing_Wikidata_to_the_Linked_Data_Web). > There you can also find how references are accessed. > > > ==Currently existing countries== > > PREFIX : <http://www.wikidata.org/entity/> > SELECT ?country ?countryName > WHERE { > ?country :P31s ?statement . > ?statement :P31v :Q3624078 . > FILTER NOT EXISTS { ?statement :P582q ?endDate } > ?country rdfs:label ?countryName FILTER(lang(?countryName)="en") > } > > Similar pattern as with the Wikipedia accounts, but now we check that a > certain qualifier (end time) does not exist. You could also find > currently married people in this way, etc. > > > ==Descendants of Queen Victoria (Q9439) == > > PREFIX : <http://www.wikidata.org/entity/> > SELECT DISTINCT * > WHERE { > :Q9439 ((^:P25c|^:P22c)+) ?person . > ?person rdfs:label ?label > FILTER(LANG(?label) = "en") > } LIMIT 1000 > > Here, ((^:P25c|^:P22c)+) is a regular expression; ^ is for changing the > direction of a property (has mother -> mother of ...); | is for "or", + > is for one or more repetitions. > > > ==Currently existing countries, ordered by the number of their current > neighbours== > > PREFIX : <http://www.wikidata.org/entity/> > SELECT ?countryName (COUNT (DISTINCT ?neighbour) AS ?neighbours) > WHERE { > ?country :P31s ?statement . > ?statement :P31v :Q3624078 . > FILTER NOT EXISTS { ?statement :P582q ?endDate } > ?country rdfs:label ?countryName FILTER(lang(?countryName)="en") > > OPTIONAL { ?country (:P47s/:P47v) ?neighbour . > ?neighbour :P31s ?statement2 . > ?statement2 :P31v :Q3624078 . > FILTER NOT EXISTS { ?statement2 :P582q ?endDate2 } > } > } ORDER BY DESC(?neighbours) > > Just to give an example of a slightly more complex query ;-) Note how we > use the expression (:P47s/:P47v) rather than :P47c to access the value > of potentially qualified statements here (since qualified statements are > currently not converted to direct :P47c statements). > > > -- > Markus Kroetzsch > Faculty of Computer Science > Technische Universität Dresden > +49 351 463 38486 > http://korrekt.org/ > > _______________________________________________ > Wikidata-l mailing list > Wikidata-l@lists.wikimedia.org > https://lists.wikimedia.org/mailman/listinfo/wikidata-l >
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