I know this is an easy question to answer, but I have been googling this for a few hours without success. Why does the following SPARQL being entered in http://dbpedia.org/snorql/ not return anything?
prefix dbo: <http://dbpedia.org/ontology/>
SELECT ?country ?city ?city_name ?country_name
WHERE {
?city rdf:type dbo:City .
?city foaf:name ?city_name .
?city dbo:country ?country .
FILTER(?country=dbpedia:Canada).
?country foaf:name ?country_name .
}
LIMIT 200
I also tried -with the same results (i.e. none)
prefix dbo: <http://dbpedia.org/ontology/>
SELECT ?country ?city ?city_name
WHERE {
?city rdf:type dbo:City .
?city foaf:name ?city_name .
?city dbo:country ?country .
?country foaf:name ?country_name .
FILTER(langMatches(lang(?country_name),"EN") && ?country_name="Canada")
}
LIMIT 200
No need for filters for an equality.
PREFIX dbo: <http://dbpedia.org/ontology/>
PREFIX foaf: <http://xmlns.com/foaf/0.1/>
PREFIX rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#>
SELECT ?country ?city ?city_name
WHERE {
?city rdf:type dbo:City ;
foaf:name ?city_name ;
dbo:country ?country .
?country foaf:name "Canada"#en .
FILTER(langMatches(lang(?city_name), "en"))
}
ORDER BY ?city_name
LIMIT 100
Test : http://linkedwiki.com/query/Filter_cities_by_country_with_DBpedia
Figured it out with some further digging.
To get the first query digging, I was using the wrong prefix. I needed to use <http://dbpedia.org/Resource> not the ontology one. This comes pre-defined in snorql - but it didn't actually have a prefix. But with some fiddling the following worked.
prefix dbo: <http://dbpedia.org/ontology/>
SELECT ?country ?city ?city_name ?country_name
WHERE {
?city rdf:type dbo:City .
?city foaf:name ?city_name .
?city dbo:country ?country .
FILTER(?country=:Canada).
?country foaf:name ?country_name .
}
LIMIT 200
As for matching on name, apparently you can't just match on a literal when using foaf. You need to add the language tag:
prefix dbo: <http://dbpedia.org/ontology/>
SELECT ?country ?city ?city_name
WHERE {
?city rdf:type dbo:City .
?city foaf:name ?city_name .
?city dbo:country ?country .
?country foaf:name ?country_name .
FILTER(langMatches(lang(?country_name),"EN") && ?country_name="Canada"#en)
}
LIMIT 200
Related
Trying to query DBpedia for a list of all countries with the dbo:longName property and the capital of each country listed but get 0 results returned. Can't see whats wrong with the query.
PREFIX dbo: <http://dbpedia.org/ontology/>
PREFIX dbr: <http://dbpedia.org/resource/>
SELECT ?country ?capital
WHERE {
?country a dbo:longName ;
dbo:capital ?capital .
}
What's missing?
You are missing that ?country has a rdf:type of dbo:Country and not dbo:longName. The right query should be:
PREFIX dbo: <http://dbpedia.org/ontology/>
PREFIX dbr: <http://dbpedia.org/resource/>
SELECT ?country ?capital
WHERE {
?x a dbo:Country.
?x dbo:longName ?country.
?x dbp:capital ?capital
}
Update
Based on your comment you want the URI's of the country and their capital. Therefore, you don't need dbo:longName, because you don't want the country label name. You will select the instances:
PREFIX dbo: <http://dbpedia.org/ontology/>
PREFIX dbr: <http://dbpedia.org/resource/>
SELECT ?country ?capital
WHERE {
?country a dbo:Country.
?country dbo:capital ?capital
}
Note that results will bring countries that are extinct. If you want to filter countries that have ended, you should get this result with:
PREFIX dbo: <http://dbpedia.org/ontology/>
PREFIX dbr: <http://dbpedia.org/resource/>
SELECT ?country ?capital
WHERE {
?country a dbo:Country.
?country dbo:capital ?capital.
FILTER NOT EXISTS { ?country dbo:dissolutionYear ?yearEnd }
}
I created this query to return all books that are notable works by George Orwell but it returns no result.
PREFIX dbo: <http://dbpedia.org/ontology/>
PREFIX dbp: <http://dbpedia.org/resource/>
PREFIX foaf: <http://xmlns.com/foaf/0.1/>
SELECT ?name ?title where {
?person foaf:name ?name .
?title dbo:author ?person .
?title dbo:notableWork dbp:George_Orwell .
}
I cannot seem to figure out why there is no result.
I am running the query in http://dbpedia.org/snorql
Don't you have the triples about notable works in the wrong order?
Try rewriting based on this working query
SELECT *
WHERE {
:George_Orwell dbo:notableWork ?title
}
.
title
:Nineteen_Eighty-Four
:Animal_Farm
You can also bind :George_Orwell to a variable and ask more about that:
SELECT *
WHERE {
values ?author { :George_Orwell } .
?author rdfs:label ?l .
?title ?p ?author .
?title rdf:type dbo:Book .
filter (lang(?l) = "en")
}
and DESCRIBE things
describe :Animal_Farm
SELECT ?name ?birth ?person ?subject
WHERE { ?person dbo:birthPlace :London . ?person
dbo:birthDate ?birth . ?person foaf:name ?name .
?person dct:subject :English_rock_singers. ?person dct:subject ?
subject. } ORDER BY ?name
This query works only if I delete the "subject".
Is there a way to query dbpedia with a category?
Though your question is not clear, I think your problem is with formatting the query and defining the prefixes. This should work:
PREFIX dbo: <http://dbpedia.org/ontology/>
PREFIX foaf: <http://xmlns.com/foaf/0.1/>
PREFIX dct: <http://purl.org/dc/terms/>
PREFIX dbr: <http://dbpedia.org/resource/>
PREFIX dbc: <http://dbpedia.org/resource/Category:>
SELECT ?name ?birth ?person ?subject WHERE {
?person dbo:birthPlace dbr:London.
?person dbo:birthDate ?birth.
?person foaf:name ?name.
?person dct:subject dbc:English_rock_singers.
?person dct:subject ?subject.
}
ORDER BY ?name
This is my sparql query to get all the country name with some property of that country.
SELECT distinct ?country ?capital ?currency ?lat ?long
WHERE {
?country rdf:type dbo:Country .
?country dbo:capital ?capital .
?country dbo:currency ?currency .
?country geo:lat ?lat.
?country geo:long ?long.
}
ORDER BY ?country
But the problem is, Some country is missing, like "Switzerland". You go to http://dbpedia.org/page/Switzerland this page you will see that it's type is country. you will also do not find exactly "Austria" rather "Austrian_Empire". Why? There is a entity called "Austria" and it is dbo:Country type.
Switzerland does not seem to have dbo:capital, which is why it's not included in the results of your query.
If you want to get even results that do not have some of the properties, use OPTIONAL:
SELECT distinct ?country ?capital ?currency ?lat ?long
WHERE {
?country rdf:type dbo:Country .
OPTIONAL
{
?country dbo:capital ?capital .
?country dbo:currency ?currency .
?country geo:lat ?lat.
?country geo:long ?long.
}
}
ORDER BY ?country
Though this query returns even entities that are not countries (but for some reason are dbo:Country), like Cinema of Switzerland.
I need to get city population by its name. I'm sure SPARQL could provide this, but I'm not sure how to write the query. I have a query which provides COuntry's capital and coordinates by it's name, so I assume it should be something similar. HELP!
PREFIX o: <http://dbpedia.org/ontology/>
PREFIX p: <http://dbpedia.org/property/>
PREFIX geo: <http://www.w3.org/2003/01/geo/wgs84_pos#>
PREFIX foaf: <http://xmlns.com/foaf/0.1/>
SELECT ?country ?population ?capital ?lat ?long WHERE {
?country a o:Country ; foaf:name "Germany"#en; o:capital [ geo:lat ?lat ; geo:long ?long ; p:name ?capital ]
}
All you need is:
PREFIX o: <http://dbpedia.org/ontology/>
PREFIX p: <http://dbpedia.org/property/>
PREFIX foaf: <http://xmlns.com/foaf/0.1/>
SELECT ?name ?pop WHERE {
?country a o:Country ;
foaf:name ?name ;
p:populationEstimate ?pop .
}
The only tricky part was finding out the name of the property that links Countries and Populations.