SPARQL queries for Pizza ontology - sparql

i have to use ROWLKit
http://www.dis.uniroma1.it/quonto/?q=node/30
(1) can anybody suggest two sparql queries for the Pizza.owl ?
(2) is this query valid ?
PREFIX rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#>
PREFIX pizza: <http://www.co-ode.org/ontologies/pizza/pizza.owl#>
SELECT *
WHERE { ?p rdf:type pizza:Pizza;
pizza:hasTopping ?t.
?t rdf:type pizza:TomatoTopping }
(3) if it is a valid query then: is the response an empty result?

SELECT DISTINCT *
WHERE {
?NombrePizza ?Relacion pizza:MushroomTopping .
?Relacion owl:inverseOf pizza:isToppingOf .
OPTIONAL {
?NombrePizza2 ?Relacion2 pizza:HamTopping .
?Relacion2 owl:inverseOf pizza:isToppingOf .
}
FILTER(?NombrePizza2 = ?NombrePizza)
}

(1) can anybody suggest two sparql queries for the Pizza.owl ?
Here are two examples:
SELECT * WHERE { ?s ?p ?o }
and:
SELECT ?class WHERE { ?class a owl:Class }
(2) is this query valid ?
Yes.
(3) if it is a valid query then: is the response an empty result?
I assume that you mean "if I query the RDF document that serialises the pizza ontology, is the response an empty result?". The answer is yes.

(2) appears to be a valid query
I don't understand part (3) of your question. (2) cannot be compared to a boolean since it returns a Result Set, if you want a boolean result then you need to use an ASK query. If an ASK query returns true then it means that there are solutions to the query in the data you are querying so it would not be an empty result.

Related

How to filter the simple Subject in a SPARQL Query

I guess I am stuck at the basics with SPARQL. Can someone help ?
I simply wnat to filter all subjects containing "Mountain" of an RDS database.
Prefix lgdr:<http://linkedgeodata.org/triplify/> Prefix lgdo:<http://linkedgeodata.org/ontology/>
Select * where {
?s ?p ?o .
filter (contains(?s, "Mountain"))
} Limit 1000
The query leads to an error:
Virtuoso 22023 Error SL001: The SPARQL 1.1 function CONTAINS() needs a string value as first argument
You can get it to "work" using:
Prefix lgdr:<http://linkedgeodata.org/triplify/> Prefix lgdo:<http://linkedgeodata.org/ontology/>
Select * where {
?s ?p ?o .
filter (contains(str(?s), "Mountain"))
} Limit 1000
Note the additional str in the query.
However, that results in
Virtuoso S1T00 Error SR171: Transaction timed out
and I am not sure how to deal with that.
But in principle in works: When you use
Limit 1
you get
s p o
http://linkedgeodata.org/ontology/MountainRescue http://www.w3.org/1999/02/22-rdf-syntax-ns#type http://www.w3.org/2002/07/owl#Class

SPARQL search query

I have some RDF data structured like this:
[ pref:ip_address "127.0.0.1" ;
pref:time "1459630844.482" ;
pref:url "https://google.com" ;
pref:user "johndoe"
] .
I need query that will return all results matching given IP, time frame (between from time and end time), url (even partial match) and user (also even partial match).
What I have now is simple query to get results based on single value, like this:
PREFIX pref: <http://something> SELECT DISTINCT * WHERE { ?u pref:user USER_VALUE . ?u ?p ?o . }
This returns all results with given user but only if given username is full match. Meaning it will return all results for johndoe if USER_VALUE is johndoe but not if it is john.
My knowledge of SPARQL is extremely limited and I appreciate any help. Thank you.
To do anything more than exact match, you need to use a FILTER and use operations like CONTAINS or REGEX.
Example:
{ ?u pref:user ?user .
?u ?p ?o .
FILTER( CONTAINS(?user, "john") )
}
There are a number of FILTER functions that may be useful including REGEX. See the spec for details.

Good SPARQL query to find all triples with a resource as subject or object

I need to find all triples on DBpedia where http://dbpedia.org/resource/Benin is a subject or object. This query gives me the output that I want in a format that works the best for me (just three variables and no blank spaces):
PREFIX : <http://dbpedia.org/resource/>
SELECT * WHERE {
?s ?p ?o
FILTER (?s=:Benin OR ?o=:Benin)
}
I get similar results if I have this query:
PREFIX : <http://dbpedia.org/resource/>
SELECT * WHERE {
{:Benin ?p ?o}
UNION
{?s ?p :Benin}
}
However, the formatting of the latter is off. It first gives me p and o output leaving s blank and then s and p leaving o blank. Also, the first query takes more time to execute. I will be grateful for an explanation of the mechanics of how the two queries work and why there is a difference in the output.
However, the formatting of the latter is off
That's because both queries have different result sets together with SELECT *. The union joins the tuples, but since some tuples are missing parts, you get skewed output.
You can resolve the problem by explicitly listing and selecting the variables:
PREFIX : <http://dbpedia.org/resource/>
SELECT ?s ?p ?o WHERE {
{
?s ?p ?o
FILTER (?s=:Benin)
}
UNION
{
?s ?p ?o .
FILTER (?o=:Benin)
}
}
Note that this is still much faster on dbpedia than the OR filter.
The union will return duplicates when a tuple matches both filter expressions (i.e. :Benin ?p :Benin).
SELECT DISTINCT would remedy that at additional cost and since it looks like the problem is non-existent, I omitted it for improved performance.
Also, the first query takes more time to execute.
That's hard to say without the result of an EXPLAIN(), but my first guess would be that the equality filter is using the index, while the OR filter is using a full table scan. Virtuoso does not seem to generate good query plans for nested filters.
Try this --
PREFIX : <http://dbpedia.org/resource/>
DESCRIBE :Benin
-- or just --
DESCRIBE <http://dbpedia.org/resource/Benin>
You can get the output in various other serializations, including N-triples.

sparql to retrieve the value of a min constraint

How can I retrieve a min constraint on a class' attribute using sparql? I have value min 1000 decimal, and I would like to get 1000
In a hypothetical world that you have such a statement:
Class: X subClassOf: hasObjectProperty min 1 Y
If you write a SPARQL query as:
SELECT *
WHERE {
?s rdfs:subClassOf ?o.
}
You must extract all the refs:subClassOf axioms. However, if you need to precise and know which ones have cardinality restrictions, you need to go further:
PREFIX rdfs: <http://www.w3.org/2000/01/rdf-schema#>
prefix : <http://example.com#>
SELECT *
WHERE {
?s rdfs:subClassOf ?o.
?o ?x ?y.
filter(?s = :X)
}
Among others, you can see the following result:
As you can see, there are 2 relevant items, one is Y and one is the number presented as a non-negative integer. Therefore, one way to get each item is to put a filter for ?x in the SPARQL query and get each one one by one out. For example, filter owl:onClass will give you ?y:
prefix : <http://example.com#>
SELECT *
WHERE {
?s rdfs:subClassOf ?o.
?o owl:onClass ?y.
filter(?s = :X)
Here is the sparql query I used following Artemis' answer
SELECT ?min
WHERE {?s rdfs:subClassOf ?o.
?o owl:minQualifiedCardinality ?min.
FILTER(?s = :value) }
And with jena, I use getLiteral("min").getFloat();

Can't execute a specific SPARQL query on DBPedia :/

On this site, for example, take the first SPARQL query and make something very similar:
PREFIX rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#>
PREFIX p: <http://dbpedia.org/property/>
SELECT *
WHERE {
?name p:name <http://dbpedia.org/resource/Olivier_Theyskens> .
}
Try to execute it: here
And I get no results. However, modify the query to the following:
PREFIX rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#>
PREFIX p: <http://dbpedia.org/property/>
SELECT *
WHERE {
?name p:name ?otherthing.
}
And I get results, even though they're not the results I want.
Why doesn't the first query work -- what am I doing wrong? :/
In this case, I think it's because you're ordering your query statement backwards.
The DBpedia resource (<http://dbpedia.org/resource/Olivier_Theyskens>) is the Entity or Subject (?s), the property (p:name) is the Attribute or Predicate (?p), and the value of that property (?name) is the Value or Object (?o).
SPARQL expects all statements to be { ?s ?p ?o }, but yours seems to be written as { ?o ?p ?s }...
To sum up, if you try this query --
PREFIX rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#>
PREFIX p: <http://dbpedia.org/property/>
SELECT *
WHERE
{
<http://dbpedia.org/resource/Olivier_Theyskens> p:name ?name .
}
-- you'll get the results I think you want.
The problem with your first query is that p:name links to Literal and you try to match a URI.
If you want your first query to work you have to to use the property http://dbpedia.org/ontology/artist that links to the URI and not the literal:
SELECT *
WHERE {
?s <http://dbpedia.org/ontology/artist> <http://dbpedia.org/resource/The_Velvet_Underground> .
}
Notice the different name space for the property <http://dbpedia.org/ontology/artist> this namespace contains ontology instead of property - ontology is the one used for object properties.