What the asterisk mean in this SPARQL query?
SELECT ?uri ?type
WHERE{
?uri a ?type.
?type rdfs:subClassOf* example:Device.
}
Does it mean "subclass of a subclass"?
Can I use it with other predicates?
An asterisk (*) after a path element means “zero or more of this element”.
If there are no other elements in the path, ?a something* ?b means that ?b might also just be ?a directly, with no path elements between them at all.
?item wdt:P31/wdt:P279* ?class.
# means:
?item wdt:P31 ?class
# or
?item wdt:P31/wdt:P279 ?class
# or
?item wdt:P31/wdt:P279/wdt:P279 ?class
# or
?item wdt:P31/wdt:P279/wdt:P279/wdt:P279 ?class
See here for more detailed answer.
The asterisk after a predicate means that you want to follow a property path with zero or more occurrences of rdfs:subClassOf.
Your phrase "subclass of a subclass" is about right, although I would say "subclasses of subclasses," because the * property path is recursive. As you can see from the technical document in AKSW's comment, there are several other property path operators that go in either direction, with or without a limit on the number of occerances (or depth.)
Here's a pretty good example from Marklogic... I think this should work within any 1.1 endpoint.
https://developer.marklogic.com/features/semantics/path-examples
Yes, property paths are applicable to any predicate/property, not just rdfs:subClassOf.
Related
The examples for counting instances at query.wikidata.org (and elsewhere) use the wdt:P31/wdt:P279* property path. For example, the number of humans in Wikidata:
SELECT (COUNT(?item) AS ?count)
WHERE {
?item wdt:P31/wdt:P279* wd:Q5 .
}
so that entities that are a subclass of human (I don't think this type exists, but think "nobel laureate", etc.) are included. But then other examples such as "women with most sitelinks and no image born in 1921 or later", which is truncated here:
SELECT ?s ?desc ?linkcount
WHERE
{
?s wdt:P31 wd:Q5 ; # human
wdt:P21 wd:Q6581072 ; # gender: female
wdt:P569 ?born .
FILTER (?born >= "1921-01-01T00:00:00Z"^^xsd:dateTime) .
...
don't use the wdt:P31/wdt:P279* property path. Are these generally oversights (or perhaps done for speed?), or is the subclass property path not actually needed in these cases and I'm too dense to see why?
How can I list properties with their values for any given DBpedia class? I'm new to this and have looked at several other questions on this but I haven't found exactly what I'm looking for.
What I'm trying to do is providing some relevant additional information to topics of conversation I have got from text mining.
Say for example the topic of conversation in a certain community is iPhones. I would like to use this word to query the DBpedia page for this word, IPhone, to get an output such as:
Type: Smartphone
Operating System: IOS
Manufacturer: Foxconn
EDIT:
Using the query from AKSW I can print the p (property?) and o (object?), although I'm still not getting the output I want. Instead of getting something like:
weight: 133.0
I get
http://dbpedia.org/property/weight:133.0
Is there a way to just get the name of the property instead of the DBpedia link?
My Code
Classes do not "have" properties with values. Instances (resp. resources or individuals) do have a relationship via a property to some value which can be an individual itself or a literal (or some anonymous instance aka blank node). And instances belong to a class. e.g. Berlin belongs to the class City
What you want is to get all outgoing values of a given resource in DBpedia:
SELECT * WHERE { <http://dbpedia.org/resource/IPhone> ?p ?o }
Alternatively, you can use SPARQL DESCRIBE, which return the data in forms of an RDF graph resp. a set of RDF triples:
DESCRIBE <http://dbpedia.org/resource/IPhone>
This might also return incoming information because it's not really specified in the W3C recommendation what has to be returned.
As stated by AKSW properties often link to other classes rather than values. If you want all properties and their values, including other classes the the below gives you the label and filters by language (put the language code you need where have put "en").
SELECT DISTINCT ?label ?o
WHERE {
<http://dbpedia.org/resource/IPhone> ?p ?o.
?p <http://www.w3.org/2000/01/rdf-schema#label> ?label .
FILTER(LANG(?label) = "" || LANGMATCHES(LANG(?label), "en"))
}
If you don't want any properties that link to other classes, then you only want datatype properties so this code could help:
SELECT DISTINCT ?label ?o
WHERE {
<http://dbpedia.org/resource/IPhone> ?p ?o.
?p <http://www.w3.org/2000/01/rdf-schema#label> ?label .
?p a owl:DatatypeProperty .
FILTER(LANG(?label) = "" || LANGMATCHES(LANG(?label), "en"))
}
Obviously this gives you far less information and functionality, but it might just be what you're after?
Edit: In reply to your comment, it is also possible to get the labels for the values, using the same technique:
SELECT DISTINCT ?label ?oLabel
WHERE {
<http://dbpedia.org/resource/IPhone> ?p ?o.
?p <http://www.w3.org/2000/01/rdf-schema#label> ?label .
?o <http://www.w3.org/2000/01/rdf-schema#label> ?oLabel
FILTER(LANG(?label) = "" || LANGMATCHES(LANG(?label), "en"))
}
Note that http://www.w3.org/2000/01/rdf-schema#label is often shortened to rdfs:label by defining prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#>
So you could also do:
prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#>
SELECT DISTINCT ?label ?oLabel
WHERE {
<http://dbpedia.org/resource/IPhone> ?p ?o.
?p rdfs:label ?label .
?o rdfs:label ?oLabel
FILTER(LANG(?label) = "" || LANGMATCHES(LANG(?label), "en"))
}
and get exactly the same result but possibly easier to read.
So my question is simple: from this URI --
http://dbpedia.org/snorql/?describe=http%3A%2F%2Fdbpedia.org%2Fresource%2FRed_Dragon_%28spacecraft%29
-- I want to extract specific things like --
rdfs:comment
rdfs:label
how to do that ?
Currently your query gets all properties, including rdfs:label and rdfs:comment. To get just those properties, substitute them for ?property, e.g.:
{ <http://dbpedia.org/resource/Red_Dragon_(spacecraft)> rdfs:label ?label .
<http://dbpedia.org/resource/Red_Dragon_(spacecraft)> rdfs:comment ?comment .
}
Also, you may want to filter for language tags, e.g., FILTER (lang(?label) = "en).
I'm trying to develop a tool in JS for tagging pictures, so I need a set of possible "things" from dbpedia. I already tryed to retrieve this way:
select ?s ?l {
?s a owl:Class .
?s rdf:type ?l
FILTER regex(str(?s), "House", "i").
}
http://dbpedia.org/snorql/?query=select+%3Fs+%3Fl+%7B%0D%0A+++%3Fs+a+owl%3AClass+.%0D%0A+++%3Fs+rdf%3Atype+%3Fl%0D%0A+++FILTER+regex%28str%28%3Fs%29%2C+%22House%22%2C+%22i%22%29.%0D%0A%7D
And also this way:
select ?label
WHERE {
?concept a skos:Concept.
?concept skos:prefLabel ?label.
FILTER regex(str(?label), "^House", "i").
}
http://dbpedia.org/snorql/?query=select+%3Flabel+%0D%0AWHERE+%7B%0D%0A++%3Fconcept+a+skos%3AConcept.%0D%0A++%3Fconcept+skos%3AprefLabel+%3Flabel.%0D%0A++FILTER+regex%28str%28%3Flabel%29%2C+%22%5EHouse%22%2C+%22i%22%29.%0D%0A%7D
In the first case, I just have "instances" of the house "thing", but not the "House" class itself. In the second one, I never retrieve the "house" and the similar thing is "houses". Any alternative for retrieving a better vocabulary based in dbpedia dataset?
If you don't bother to restrict yourself to owl:Thing or to skos:Concept, you can just get things that have a label that contains "house". Rather than using regex, I chose to use contains and lcase, since a string containment could be less expensive than invoking a full regular expression processor.
select ?thing ?label where {
?thing rdfs:label ?label .
filter contains(lcase(?label), "house")
}
SPARQL results (limited to 200)
I am trying to run a query on dbpedia using SPARQL syntax, to look for all pages of a certain template. Doesn't seem to be work, I am looking for all pages with dbpprop:wikiPageUsesTemplate. Does anyone know how to correct this to properly look for templates?
SELECT ?name ?member_Of ?country ?lat ?lng ?link
WHERE {
?x dbpprop:wikiPageUsesTemplate "dbpedia:Template:Infobox_settlement" .
?x a <http://dbpedia.org/ontology/Settlement> .
?x foaf:name ?name .
?x dbpedia-owl:isPartOf ?member_Of.
?x dbpedia-owl:country ?country.
?x geo:lat ?lat .
?x geo:long ?lng .
?x foaf:isPrimaryTopicOf ?link .
}
LIMIT 2500 OFFSET 0
I've also attempted to run it just by the dbprop to no avail.
SELECT * WHERE { ?page dbpprop:wikiPageUsesTemplate <http://dbpedia.org/resource/Template:Infobox_settlement> . ?page dbpedia:name ?name .}
If anyone is trying to do a similar thing, it is also possible via the wiki api, where you can pagananate over all results. http://en.wikipedia.org/w/api.php?action=query&list=embeddedin&eititle=Template:Infobox_settlement
There are at least two problems: (i) you need to use IRIs in places, and not strings; and (ii) you need to use properties that DBpedia uses.
Use IRIs
In
?x a <http://dbpedia.org/ontology/Settlement> .
and
?x foaf:isPrimaryTopicOf ?link .
you've demonstrated that you know that URIs need to be written in full with < and >, or abbreviated with a prefix. However,
?x dbpprop:wikiPageUsesTemplate "dbpedia:Template:Infobox_settlement" .
certainly isn't going to work. It's legal SPARQL, because a string can be the object of a triple, but you almost certainly want an IRI.
Use DBpedia's vocabulary
A query with dbpprop:wikiPageUsesTemplate like this returns no results:
select distinct ?template where {
[] dbpprop:wikiPageUsesTemplate ?template
}
SPARQL results
That's easy enough to check, and quickly confirms that there's no data that can possibly match your query. Where did you find this property? Have you seen it used somewhere? I'm not confident that you can query DBpedia based on infobox templates. DBpedia is not the same as Wikipedia, and even if the Wikipedia API supports it, it doesn't mean that DBpedia has a counterpart. There is a note on DBpedia Data Set Properties that says:
http://xx.dbpedia.org/property/wikiPageUsesTemplate (will be changed to http://dbpedia.org/ontology/wikiPageUsesTemplate)
but that latter property doesn't seem to be in use on the endpoints either. See my answer to Syntax for Sparql query for pages with specific infobox for more details.