I'm developing my own Fuseki endpoint from some DBpedia data.
I'm in doubt on how to aggregate properties related to a single resource.
SELECT ?name ?website ?abstract ?genre ?image
WHERE{
VALUES ?s {<http://dbpedia.org/resource/Attack_Attack!>}
?s foaf:name ?name ;
dbo:abstract ?abstract .
OPTIONAL { ?s dbo:genre ?genre } .
OPTIONAL { ?s dbp:website ?website } .
OPTIONAL { ?s dbo:image ?image } .
FILTER LANGMATCHES(LANG(?abstract ), "en")
}
SPARQL endpoint: http://dbpedia.org/sparql/
This query returns 2 matching results. They are different just for the dbo:genre value. There is a way I can query the knowledge base and retrieving a single result with a list of genres?
#chrisis's query works well on the DBpedia SPARQL Endpoint, which is based on Virtuoso.
However, if you are using Jena Fuseki, you should use more conformant syntax:
PREFIX dbo: <http://dbpedia.org/ontology/>
PREFIX dbp: <http://dbpedia.org/property/>
SELECT
?name
(SAMPLE(?website) AS ?sample_website)
(SAMPLE(?abstract) AS ?sample_abstract)
(SAMPLE(?image) AS ?sample_image)
(GROUP_CONCAT(?genre; separator=', ') AS ?genres)
WHERE {
VALUES (?s) {(<http://dbpedia.org/resource/Attack_Attack!>)}
?s foaf:name ?name ;
dbo:abstract ?abstract .
OPTIONAL { ?s dbo:genre ?genre } .
OPTIONAL { ?s dbp:website ?website } .
OPTIONAL { ?s dbo:image ?image} .
FILTER LANGMATCHES(LANG(?abstract ), "en")
} GROUP BY ?name
The differences from the #chrisis's query are:
Since GROUP_CONCAT is an aggregation function, it might be used with GROUP BY only;
Since GROUP BY is used, all non-grouping variables should be aggregated (e.g. via SAMPLE);
GROUP_CONCAT syntax is slightly different.
In Fuseki, these AS in the projection are in fact superfluous: see this question and comments.
Yes, the GROUP_CONCAT() function is what you want.
SELECT ?name ?website ?abstract (GROUP_CONCAT(?genre,',') AS ?genres) ?image
WHERE{
<http://dbpedia.org/resource/Attack_Attack!> a dbo:Band ;
foaf:name ?name;
dbo:abstract ?abstract .
OPTIONAL{ <http://dbpedia.org/resource/Attack_Attack!> dbo:genre ?genre } .
OPTIONAL{ <http://dbpedia.org/resource/Attack_Attack!> dbp:website ?website} .
OPTIONAL{ <http://dbpedia.org/resource/Attack_Attack!> dbo:image ?image} .
FILTER LANGMATCHES(LANG(?abstract ), "en")
}
Related
Why can get results with this query:
SELECT *
WHERE {
?person rdfs:label "Kirk Douglas"#en;
dbo:birthPlace ?place. # With dbp: too
}
but not with another one:
SELECT *
WHERE {
?person rdfs:label "Kirk Douglas"#en;
dbo:starring ?film.
}
I'm following tags in https://dbpedia.org/page/Kirk_Douglas
Some tip to understand it.
Thx!
In dbr:Kirk_Douglas you can read:
dbo:birthPlace dbr:Amsterdam_(city),_New_York
...
is dbo:starring of dbr:The_Light_at_the_Edge_of_the_World
dbr:Cast_a_Giant_Shadow
dbr:Two-Fisted_Tales_(film)
...
where is dbo:starring of is a way of simulating an inverse property for dbo:starring.
Indeed, in dbo:starring you can read:
rdfs:domain dbo:Work
...
rdfs:range dbo:Actor
This means that you shouldn't build triples like ?actor dbo:starring ?work, while ?work dbo:starring ?actor is a valid triple.
So your query should be something like:
SELECT *
WHERE {
?person rdfs:label "Kirk Douglas"#en .
?film dbo:starring ?person .
}
I would like to add a condition to a query, so that, if a result is empty, it fills it with a result of another query.
For example : If a owl:Class has no "skos:definition", I would like to replace it by a "rdfs:comment"
Is this possible ?
Thank you !
COALESCE is can help, especially as you get more choices from skos:prefLabel, skos:altLabel and more.
OPTIONAL { ?property rdfs:label ?label }
OPTIONAL { ?property skos:definition ?definition .}
# ... other ways to choose ?comment ...
BIND ( COALESCE(?definition, ?label, "Unknown") AS ?comment )
COALESCE allows expressions (unlike BOUND)
https://www.w3.org/TR/sparql11-query/#func-coalesce
I found something with BIND (IF(BOUND(...) ..., ...) AS ...) statement.
SELECT DISTINCT ?type ?property ?comment ?propertyType ?domain
WHERE {
?property rens:hasAttributeType ?propertyType .
?property rens:hasForDomain ?domain .
?property rdf:type ?type .
?property rdfs:label ?label .
OPTIONAL {?property skos:definition ?definition .}
BIND(IF(BOUND(?definition), ?definition, ?label) AS ?comment) .
}
Is this the better way ?
I am wondering how I can use in sparql query when I have a word like :
Robert J. O'Neill
I am looking for the resource that have the multiword unit with quota or unicode character in the Label property.
SELECT DISTINCT ?resource ?abstract
WHERE {?resource rdfs:label ?s.
?s <bif:contains> "'Robert J. O'Neill'"
?resource dbo:abstract ?abstract
}
'''
Here is the query that will return all the elements that have "Robert J. O'Neill" as label.
SELECT DISTINCT ?s WHERE
{
?s rdfs:label ?label .
FILTER(regex(?label, "Robert J. O'Neill", "i"))
}
If you are sure that you need a specific string matching. This is faster :
SELECT DISTINCT ?s WHERE
{
?s rdfs:label ?label .
?label bif:contains "Robert J. O'Neill"
}
But be aware that, Virtuoso for example doesnt support such a query because of the spaces in the string. So an alternative is to avoid it as :
SELECT DISTINCT * WHERE
{
?s rdfs:label ?label .
?label bif:contains "Robert" .
FILTER (CONTAINS(?label, " J. O'Neill"))
}
I found following code faster that the regex:
SELECT ?s WHERE { ?s rdfs:label ?o FILTER ( bif:contains ( ?o, '"Robert" AND "J." AND "Neill"' ) ) }
I am trying to query dbpedia to get some people data and I don't have subjects just names of the people I want to query and their birth/death dates.
I am trying to do a query along these lines. I want the name, birth date, death date and thumbnail of everyone with the surname Presley. What I then intend to do is loop through the results returned and find the best match for Elvis Presley 1935-1977 which is the data I have.
PREFIX dbo: <http://dbpedia.org/ontology/>
SELECT ?Name ?thumbnail ?birthDate ?deathDate WHERE {
{
dbo:name ?Name ;
dbo:birthDate ?birthDate ;
dbo:birthDate ?deathDate ;
dbo:thumbnail ?thumbnail ;
FILTER contains(?Name#en, "Presley")
}
What is the best way to construct my sparql query?
UPDATE:
I have put together this query which seems to work to some extent but I don't entirely understand it, and I can't figure out the contains, but it does at least run and return results.
PREFIX rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#>
PREFIX foaf: <http://xmlns.com/foaf/0.1/>
PREFIX dbo: <http://dbpedia.org/ontology/>
SELECT ?subject ?thumbnail ?birthdate ?deathdate WHERE {
{
?subject rdfs:label "Elvis Presley"#en ;
dbo:thumbnail ?thumbnail ;
dbo:birthDate ?birthdate ;
dbo:deathDate ?deathdate ;
a owl:Thing .
}
UNION
{
?altName rdfs:label "Elvis Presley"#en ;
dbo:thumbnail ?thumbnail ;
dbo:birthDate ?birthdate ;
dbo:deathDate ?deathdate ;
dbo:wikiPageRedirects ?s .
}
}
Some entities might not have all of that information, so it's better to use optional. You can use foaf:surname to check for surname directly.
select * where {
?s foaf:surname "Presley"#en
optional { ?s dbo:name ?name }
optional { ?s dbo:birthDate ?birth }
optional { ?s dbo:deathDate ?death }
optional { ?s dbo:thumbnail ?thumb }
}
I have to use this Spaql query to retrive information about a person, my problem is to break the optional construct up into multiple optional constructs.
PREFIX rdfs: <http://www.w3.org/2000/01/rdf-schema#>
PREFIX dbo: <http://dbpedia.org/ontology/>
PREFIX dbpprop: <http://dbpedia.org/property/>
PREFIX foaf: <http://xmlns.com/foaf/0.1/>
SELECT DISTINCT ?label ?abstract ?placeOfBirth
?birthPlace ?birthDate ?page ?thumbnail
WHERE {
<http://dbpedia.org/resource/Ismail_Kadare> rdfs:label ?label ;
dbo:abstract ?abstract ;
foaf:page ?page .
OPTIONAL {
<http://dbpedia.org/resource/Ismail_Kadare> dbpprop:placeOfBirth ?placeOfBirth ;
dbpprop:birthPlace ?birthPlace ;
dbo:birthDate ?birthDate ;
dbo:thumbnail ?thumbnail .
}
FILTER (LANG(?label) = 'en')
FILTER (LANG(?abstract) = 'en')
}
LIMIT 1
Splitting the OPTIONAL pattern into parts
The pattern
<http://dbpedia.org/resource/Ismail_Kadare> dbpprop:placeOfBirth ?placeOfBirth ;
dbpprop:birthPlace ?birthPlace ;
dbo:birthDate ?birthDate ;
dbo:thumbnail ?thumbnail .
is shorthand for four triple patterns:
<http://dbpedia.org/resource/Ismail_Kadare> dbpprop:placeOfBirth ?placeOfBirth .
<http://dbpedia.org/resource/Ismail_Kadare> dbpprop:birthPlace ?birthPlace .
<http://dbpedia.org/resource/Ismail_Kadare> dbo:birthDate ?birthDate .
<http://dbpedia.org/resource/Ismail_Kadare> dbo:thumbnail ?thumbnail .
Instead of OPTIONAL { …first pattern… }, you just need to use four optional blocks, one for each of the four triple patterns:
optional { <http://dbpedia.org/resource/Ismail_Kadare> dbpprop:placeOfBirth ?placeOfBirth }
optional { <http://dbpedia.org/resource/Ismail_Kadare> dbpprop:birthPlace ?birthPlace }
optional { <http://dbpedia.org/resource/Ismail_Kadare> dbo:birthDate ?birthDate }
optional { <http://dbpedia.org/resource/Ismail_Kadare> dbo:thumbnail ?thumbnail }
Other issues
It's worth nothing that language matching is a bit more complicated than string matching, so rather than
FILTER (LANG(?label) = 'en')
FILTER (LANG(?abstract) = 'en')
you should really be using
filter(langMatches(lang(?label),'en'))
filter(langMatches(lang(?abstract),'en'))
which allows you to retrieve results that use different language tags that are all English.
select distinct and limit 1 aren't both necessary
Notice that select distinct ensures that you don't have any duplicate rows in your results. However, limit 1 means that you'll only have one result at most anyhow, so there won't be any duplicates to remove.
Standard Namespaces
It looks like you're querying against DBpedia, so it might be worthwhile to use the same namespace prefixes that the public endpoint defines, so that you can copy and paste queries and experiment more easily. Doing that (and using a values ?x { dbpedia:Ismail_Kadare } to avoid some typing, we end up with this query:
select ?label ?abstract ?placeOfBirth ?birthPlace ?birthDate ?page ?thumbnail
where {
values ?x { dbpedia:Ismail_Kadare }
?x rdfs:label ?label ;
dbpedia-owl:abstract ?abstract ;
foaf:page ?page .
optional { ?x dbpprop:placeOfBirth ?placeOfBirth }
optional { ?x dbpprop:birthPlace ?birthPlace }
optional { ?x dbpedia-owl:birthDate ?birthDate }
optional { ?x dbpedia-owl:thumbnail ?thumbnail }
filter langMatches(lang(?label),'en')
filter langMatches(lang(?abstract),'en')
}
limit 1
The DBpedia endpoint won't return anything for that query, but that's because http://dbpedia.org/resource/Ismail_Kadare doesn't have a foaf:page property, not because the query is malformed. I don't know whether you're actually running this against DBpedia or not, so that may or not matter.