I want to query all triples with a certain predicate p. The query should only return triples (s,p,o) where the other direction (o,p,s) does not exist.
How can I make such a query?
That's pretty easy:
SELECT ?s ?p ?o {
?s ?p ?o
MINUS { ?o ?p ?s }
}
FILTER NOT EXISTS instead of MINUS would also work. Replace ?p in the query with the desired predicate, or use something like FILTER (?p=ex:myPredicate) if you want ?p in the result.
My goal is to graphically represent the S->P->O relations within a depth two edges from the specified resource, p:Person_1. I want all relations within that path length to be returned from my query as ?s, ?p, ?o for further processing in my graphical application.
I tried the first query below which gives me my first set of ?s ?p ?o with repeats, then ?p2, ?o2, ?p3, ?o3 as additional columns in the result. I want to bind ?p2 and ?p3 to ?p, ?o2 and ?o3 to ?o.
SELECT *
WHERE {
p:Person_1 ?p ?o .
BIND("p:Person_1" as ?s)
OPTIONAL{
?o ?p2 ?o2 .
}
OPTIONAL{
?o2 ?p3 ?o3 .
}
}
Then, based on How do I construct get the whole sub graph from a given resource in RDF Graph?, I tried using CONSTRUCT to return the graph.
PREFIX p: <http://www.example.org/person/>
PREFIX x: <example.org/foo/>
construct { ?s ?p ?o }
FROM <http://localhost:8890/MYGRAPH>
where { p:Person_1 (x:|!x:)* ?s .
?s ?p ?o .
}
I am using Virtuoso and I get the error:
Virtuoso 37000 Error SP031: SPARQL compiler: Variable ?_::trans_subj_9_3 in T_IN list is not a value from some triple
I could post-process the result from my first query but I want to learn how to do this correctly with SPARQL, preferably on Virtuoso.
Update after testing the advice from #AKSW :
Both CONSTRUCT and SELECT statements work with the pattern suggested.
CONSTRUCT { ?s ?p ?o }
FROM <http://localhost:8890/MYGRAPH>
where { p:Person_1 (x:foo|!x:bar)* ?s .
?s ?p ?o .
} LIMIT 100
and:
SELECT s ?p ?o
FROM <http://localhost:8890/MYGRAPH>
where { p:Person_1 (x:foo|!x:bar)* ?s .
?s ?p ?o .
} LIMIT 100
The SELECT results in several duplicates that cannot be removed using DISTINCT, which results in an error that I assume is due to the 'datatype' of some of the returned values.
Virtuoso 22023 Error SR066: Unsupported case in CONVERT (DATETIME -> IRI_ID)
It appears some post-SPARQL processing is in order.
This gets me most of the way there. Still hoping I can find a solution for SPARQL that is like Cypher's "number of hops away" :
OPTIONAL MATCH path=s-[*1..3]-(o)
Here is a SPARQL query that works in Virtuoso. Note the SPARQL W3C standard does not support this syntax and it will fail in other triplestores.
PREFIX p: <http://www.example.org/person/>
PREFIX x: <example.org/foo/>
# CONSTRUCT {?s ?p ?o} # If you wish to return the graph
SELECT ?s ?p ?o # To return the triples
FROM <http://localhost:8890/MYGRAPH>
where { p:Person_1 (x:foo|!x:bar){1,3} ?s .
?s ?p ?o .
}LIMIT 100
See also K. Idehen's wiki entry here: http://linkedwiki.com/exampleView.php?ex_id=141
And thanks to #Joshua Taylor for advice in the same area.
Working Drafts of SPARQL 1.1 Property Paths included the {n,m} operator for handling this issue, which was implemented (and will remain supported) in Virtuoso. Here's a tweak to #tim's response.
Live SPARQL Query Results Page using the DBpedia endpoint (which is a Virtuoso instance).
Live SPARQL Query Definition Page that opens up query source code in the default DBpedia query editor.
Actual Query Example:
PREFIX rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#>
SELECT DISTINCT ?s AS ?Entity
?o AS ?Category
WHERE {
?s rdf:type <http://dbpedia.org/ontology/AcademicJournal> ;
rdf:type{1,3} ?o
}
LIMIT 100
Should you be looking for LinkedIn-like presentation of Contact Networks and Degrees of Separation between individuals, here is an example using Virtuoso-specific SPARQL Extensions that solve this particular issue:
SELECT ?o AS ?WebID
((SELECT COUNT (*) WHERE {?o foaf:knows ?xx})) AS ?contact_network_size
?dist AS ?DegreeOfSeparation
<http://www.w3.org/People/Berners-Lee/card#i> AS ?knowee
WHERE
{
{
SELECT ?s ?o
WHERE
{
?s foaf:knows ?o
}
} OPTION (TRANSITIVE, t_distinct, t_in(?s), t_out(?o), t_min (1), t_max (4), t_step ('step_no') AS ?dist) .
FILTER (?s= <http://www.w3.org/People/Berners-Lee/card#i>)
FILTER (isIRI(?s) and isIRI(?o))
}
ORDER BY ?dist DESC (?contact_network_size)
LIMIT 500
Note: this approach is the only way (at the current time) to expose actual relational hops between entities in an Entity Relationship Graph that includes Transitive relations.
Live Link to Query Results
Live Link to Query Source Code
Bearing in mind that the r{n,m} operator was deprecated in the final SPARQL 1.1 (but will remain supported in Virtuoso), you can use r/r?/r? instead of r{1,3}, if you want to work strictly off the current spec:
PREFIX rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#>
SELECT DISTINCT ?s AS ?Entity
?o AS ?Category
WHERE {
?s rdf:type <http://dbpedia.org/ontology/AcademicJournal> ;
rdf:type / rdf:type? / rdf:type? ?o
}
LIMIT 100
Here's a live example, against the DBpedia instance hosted in Virtuoso.
Is it possible to get, in a single query, a count of the number of multiple relations? e.g.
SELECT (COUNT(?friendid) as ?friends) (COUNT(?cousinid) as ?cousins) (COUNT(?sonid) as ?sons)
WHERE
{
ex:person1 ex:friendOf ?friendid .
ex:person1 ex:cousinOf ?cousinid .
ex:person1 ex:fatherOf ?sonid .
}
If a complex query with multiple queries is needed, is this -in theory, of course- supposed to be faster than executing different SELECTs?
Following query retrieves ALL the predicates and their numbers:
SELECT ?p (COUNT(?p) as ?pCount) WHERE { ex:person1 ?p ?o} GROUP BY ?p
This one restricts the predicates (AKSW's suggestion):
SELECT ?p (COUNT(?p) as ?pCount) WHERE { ex:person1 ?p ?o. VALUES (?p) {(:p1)}} GROUP BY ?p
Here is an example:
SELECT ?p (COUNT(?p) as ?pCount) WHERE
{
<http://dbpedia.org/resource/Category:Museums_in_Italy> ?p ?o .
VALUES (?p) {(skos:altLabel) (owl:sameAs)}
}
GROUP BY ?p
And here are the results:
Results
I run a SPARQL construct query on DBpedia endpoint. The query is for getting all the information describing all movies:
construct
{
?s ?p ?o
}
where
{
?s a <http://dbpedia.org/ontology/Film>.
{
SELECT ?s ?p ?o
{
?s ?p ?o
}
group by ?s ?p
}
}
The query works fine. The problem is DBpedia stops it at 10.000. I tried to make the offset 0 but it does make any difference. Also, I don't think chrome would support to display a million triple. Therefore, I was thinking if there is a solution, or a tip, so I can retrieve the data by segments, meaning I start from where I stopped previously.
You could try ORDER BY, LIMIT and OFFSET. You can also simplify your query significantly:
construct
{
?s ?p ?o
}
where
{
?s a <http://dbpedia.org/ontology/Film> .
?s ?p ?o
} ORDER BY ?s ?p ?o
OFFSET 0 LIMIT 1000
Then change the OFFSET for each "segment".
I am trying to delete some triples using a SPARQL query.
delete ?s ?p ?o {<http://www.example.org/test/unit213> ?p ?o.
?s ?p ?o}
I get the following error:
Executing query failed: MALFORMED QUERY: Parse error: unexpected terminal varname (value: ?s). Expected terminals: ({ qname qname_ns q_iri_ref from data).
What is the problem?
You need to wrap those triples in the delete:
delete { ?s ?p ?o } ...