I have a class named WeatherPatterns, it has many subclasses and the subclasses have named Individuals/ Instances.
I want a sparql query to retrieve all instances of WeatherPatterns that have relation with each other. For example, the output triples should be listed like the following.
Cloud produces Rain
Rain causes Flood
How to make this query? thanks in advance
Without your data, we can't make an exact query, but if you're looking for relationships between things that are direct or indirect instances of WeatherPatterns, that's not too hard:
select ?s ?p ?o {
#-- Make sure that ?s and ?o are
#-- instance of WeatherPatterns
#-- or its subclasses.
?s a/rdfs:subClassOf* :WeatherPatterns .
?o a/rdfs:subClassOf* :WeatherPatterns .
#-- Find relationships between
#-- ?s and ?o.
?s ?p ?o .
}
The property path ?s a/rdfs:subClassOf* :WeatherPatterns uses a as the standard abbreviation for rdf:type, and matches when ?s belongs to a class that is related by a chain of rdfs:subClassOf properties to :WeatherPatterns. (The chain can be of length zero, which means that ?s is a direct instance of :WeatherPatterns.) If you want to combine the two checks into one, you can also do:
:WeatherPatterns ^(a/rdfs:subClassOf*) ?s, ?o .
Related
I want to query an ontology and get all its object properties, I have tried this query but it doesn't work
select ?p
where { ?s ?p ?o.
?s rdf:type owl:ObjectProperty.
}
Anyone can help me please ?
whenever I start using SQL I tend to throw a couple of exploratory statements at the database in order to understand what is available, and what form the data takes.
e.g.
show tables
describe table
select * from table
Could anyone help me understand the way to complete a similar exploration of an RDF datastore using a SPARQL endpoint?
Well, the obvious first start is to look at the classes and properties present in the data.
Here is how to see what classes are being used:
SELECT DISTINCT ?class
WHERE {
?s a ?class .
}
LIMIT 25
OFFSET 0
(LIMIT and OFFSET are there for paging. It is worth getting used to these especially if you are sending your query over the Internet. I'll omit them in the other examples.)
a is a special SPARQL (and Notation3/Turtle) syntax to represent the rdf:type predicate - this links individual instances to owl:Class/rdfs:Class types (roughly equivalent to tables in SQL RDBMSes).
Secondly, you want to look at the properties. You can do this either by using the classes you've searched for or just looking for properties. Let's just get all the properties out of the store:
SELECT DISTINCT ?property
WHERE {
?s ?property ?o .
}
This will get all the properties, which you probably aren't interested in. This is equivalent to a list of all the row columns in SQL, but without any grouping by the table.
More useful is to see what properties are being used by instances that declare a particular class:
SELECT DISTINCT ?property
WHERE {
?s a <http://xmlns.com/foaf/0.1/Person>;
?property ?o .
}
This will get you back the properties used on any instances that satisfy the first triple - namely, that have the rdf:type of http://xmlns.com/foaf/0.1/Person.
Remember, because a rdf:Resource can have multiple rdf:type properties - classes if you will - and because RDF's data model is additive, you don't have a diamond problem. The type is just another property - it's just a useful social agreement to say that some things are persons or dogs or genes or football teams. It doesn't mean that the data store is going to contain properties usually associated with that type. The type doesn't guarantee anything in terms of what properties a resource might have.
You need to familiarise yourself with the data model and the use of SPARQL's UNION and OPTIONAL syntax. The rough mapping of rdf:type to SQL tables is just that - rough.
You might want to know what kind of entity the property is pointing to. Firstly, you probably want to know about datatype properties - equivalent to literals or primitives. You know, strings, integers, etc. RDF defines these literals as all inheriting from string. We can filter out just those properties that are literals using the SPARQL filter method isLiteral:
SELECT DISTINCT ?property
WHERE {
?s a <http://xmlns.com/foaf/0.1/Person>;
?property ?o .
FILTER isLiteral(?o)
}
We are here only going to get properties that have as their object a literal - a string, date-time, boolean, or one of the other XSD datatypes.
But what about the non-literal objects? Consider this very simple pseudo-Java class definition as an analogy:
public class Person {
int age;
Person marriedTo;
}
Using the above query, we would get back the literal that would represent age if the age property is bound. But marriedTo isn't a primitive (i.e. a literal in RDF terms) - it's a reference to another object - in RDF/OWL terminology, that's an object property. But we don't know what sort of objects are being referred to by those properties (predicates). This query will get you back properties with the accompanying types (the classes of which ?o values are members of).
SELECT DISTINCT ?property, ?class
WHERE {
?s a <http://xmlns.com/foaf/0.1/Person>;
?property ?o .
?o a ?class .
FILTER(!isLiteral(?o))
}
That should be enough to orient yourself in a particular dataset. Of course, I'd also recommend that you just pull out some individual resources and inspect them. You can do that using the DESCRIBE query:
DESCRIBE <http://example.org/resource>
There are some SPARQL tools - SNORQL, for instance - that let you do this in a browser. The SNORQL instance I've linked to has a sample query for exploring the possible named graphs, which I haven't covered here.
If you are unfamiliar with SPARQL, honestly, the best resource if you get stuck is the specification. It's a W3C spec but a pretty good one (they built a decent test suite so you can actually see whether implementations have done it properly or not) and if you can get over the complicated language, it is pretty helpful.
I find the following set of exploratory queries useful:
Seeing the classes:
select distinct ?type ?label
where {
?s a ?type .
OPTIONAL { ?type rdfs:label ?label }
}
Seeing the properties:
select distinct ?objprop ?label
where {
?objprop a owl:ObjectProperty .
OPTIONAL { ?objprop rdfs:label ?label }
}
Seeing the data properties:
select distinct ?dataprop ?label
where {
?dataprop a owl:DatatypeProperty .
OPTIONAL { ?dataprop rdfs:label ?label }
}
Seeing which properties are actually used:
select distinct ?p ?label
where {
?s ?p ?o .
OPTIONAL { ?p rdfs:label ?label }
}
Seeing what entities are asserted:
select distinct ?entity ?elabel ?type ?tlabel
where {
?entity a ?type .
OPTIONAL { ?entity rdfs:label ?elabel } .
OPTIONAL { ?type rdfs:label ?tlabel }
}
Seeing the distinct graphs in use:
select distinct ?g where {
graph ?g {
?s ?p ?o
}
}
SELECT DISTINCT * WHERE {
?s ?p ?o
}
LIMIT 10
I often refer to this list of queries from the voiD project. They are mainly of a statistical nature, but not only. It shouldn't be hard to remove the COUNTs from some statements to get the actual values.
Especially with large datasets, it is important to distinguish the pattern from the noise and to understand which structures are used a lot and which are rare. Instead of SELECT DISTINCT, I use aggregation queries to count the major classes, predicates etc. For example, here's how to see the most important predicates in your dataset:
SELECT ?pred (COUNT(*) as ?triples)
WHERE {
?s ?pred ?o .
}
GROUP BY ?pred
ORDER BY DESC(?triples)
LIMIT 100
I usually start by listing the graphs in a repository and their sizes, then look at classes (again with counts) in the graph(s) of interest, then the predicates of the class(es) I am interested in, etc.
Of course these selectors can be combined and restricted if appropriate. To see what predicates are defined for instances of type foaf:Person, and break this down by graph, you could use this:
SELECT ?g ?pred (COUNT(*) as ?triples)
WHERE {
GRAPH ?g {
?s a foaf:Person .
?s ?pred ?o .
}
GROUP BY ?g ?pred
ORDER BY ?g DESC(?triples)
This will list each graph with the predicates in it, in descending order of frequency.
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.
Imagine you do something crazy and store your object-oriented model as an RDF graph.
shows a simplified example of the inheritance hierarchy and the associated attributes.
In practice, you get such graph structure if you translate some UML class diagram into RDFS.
The question is: what SPARQL query can deliver all the predicate-object pairs necessary to instantiate a particular resource of "Class C". In other words: how do you get all the predicate-object pairs along the whole inheritance chain (only single inheritance).
Given this diagram, the predicate-object pairs of all members of the class:ClassC is simply:
SELECT ?inst ?p ?o
WHERE {
?inst a :ClassC .
Inst ?p ?o .
Keep in mind that there is not property inheritance in RDF/RDFS. If you want to find all of property/values pairs for ClassA with entailments for subclasses then useL
SELECT ?inst ?p ?o
WHERE {
?cls rdfs:subClassOf* :ClassA .
?inst a ?cls .
?inst ?p ?o
}
In this respect, RDFS works a bit backwards of one's expectations of OO inheritance.
With the info from #scotthenninger the following query did the job:
SELECT ?p ?o
WHERE {
:ClassC rdfs:subClassOf* ?anySuperClass .
?anySuperClass ?p ?o .
}
edit:
Similar query gets all the self-defined properties and their range along the inheritance chain:
SELECT ?prop ?obj
WHERE {
:ClassC rdfs:subClassOf* ?anySuperClass .
?prop rdfs:domain ?anySuperClass .
?prop rdfs:range ?obj .
}
End results combined:
foo:ID xsd:string
foo:name xsd:string
rdfs:comment xsd:string
foo:similarTo :ClassD
I have an ontology where arc_cfp is an individual of class Arc. I would like to know how could I get all the data properties of the individual, given that I have the individual's URI?
Basically, I am doing this:
SELECT ?idRef ?name ?src ?dst ?perf
WHERE
{
?x rdf:type http://www.semanticweb.org/ontologies/2012/1/graph.owl#arc_cfp .
?x graph:idRef_arc ?idRef .
?x graph:name_arc ?name .
?x graph:hasSource ?src .
?x graph:hasDestination ?dst .
?x graph:hasPerformatif ?perf .
}
I am pretty sure, using rdf:type is the problem. But, I have no idea what I need to use.
Thanks.
~Codera
Assuming you want a purely exploratory query of the form "give me all the triples about a subject" it should look the following:
SELECT *
WHERE
{
<http://example.org/SomeThing> ?p ?o
}
This will give you all predicate object pairs associated with the constant URI you pass in. If you are interesting in incoming as well as outgoing properties you could do the following instead:
SELECT *
WHERE
{
{ <http://example.org/SomeThing> ?p ?o }
UNION
{ ?s ?p <http://example.org/SomeThing> }
}
You can also use a DESCRIBE query to grab all the RDF data about a Resource.
PREFIX rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#> .
DESCRIBE ?x
WHERE
{
?x rdf:type http://www.semanticweb.org/ontologies/2012/1/graph.owl#arc_cfp .
}
P.S. Don't forget to put prefixes in your queries.