- From: Dau, Frithjof <frithjof.dau@sap.com>
- Date: Fri, 12 Jun 2009 17:51:23 +0200
- To: "Samuel Pedro" <samuelcpspam@gmail.com>, "Stephane Corlosquet" <scorlosquet@gmail.com>, "Lee Feigenbaum" <lee@thefigtrees.net>, <public-sparql-dev@w3.org>
- Message-ID: <EDFFA9D51148B34FAA0B828A82AAE70C022B9593@dewdfe1g.wdf.sap.corp>
Hi Samuel,
with SPARQL you can essentially query subgraphs of a given graph. In
your "OWL-graph", you have a node "...#Meat". With SPARQL, you can query
other nodes and the properties which relate these nodes to you
"...#Meat"-node. Anyhow, the only property which relates your
"...#Meat"-node to ther nodes is the "rdfs:subClassOf"-property,
relating your "...#Meat"-node to its super- and subclasses (depending on
whether your "...#Meat"-node is the subject or object of a (x
rdfs:subClassOf y) triple).
I guess what you have in mind is something like: The class is called
"Meat", so let's query for that name. Nope, does not work. The name of
the class is a part of the node-URI, and you cannot query parts of these
-let's say- URI-string. So, if you want to query classes by its names,
you *must* make the name in the ontology explicit by using a property.
The most common approach is the "rdfs:label"-attribute. Iy you use it
-and you do it for your "...#Pig"-class, you explicitely relate the name
"Pig" (a literal) to the class by the rdfs:label-property. Now you have
the situation that the class is linked to its name by use of nodes and
properties, and thus you can query it.
I sugges you have a look at your ontology with an RDF-visualizer (like
IsaViz), keep in mind that you can only query for graph patterns, and
then you will hopefully understand why your initial query does not work.
Cheers
Frithjof
________________________________
Von: public-sparql-dev-request@w3.org
[mailto:public-sparql-dev-request@w3.org] Im Auftrag von Samuel Pedro
Gesendet: Freitag, 12. Juni 2009 17:35
An: Stephane Corlosquet; Lee Feigenbaum; public-sparql-dev@w3.org
Betreff: Re: Sparql query help
Ok, tried to send as a attachment but probably something went wrong, i
will post here:
<?xml version="1.0"?>
<rdf:RDF
xmlns:xsp="http://www.owl-ontologies.com/2005/08/07/xsp.owl#"
xmlns="http://www.owl-ontologies.com/testFood2.owl#"
xmlns:swrlb="http://www.w3.org/2003/11/swrlb#"
xmlns:swrl="http://www.w3.org/2003/11/swrl#"
xmlns:protege="http://protege.stanford.edu/plugins/owl/protege#"
xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
xmlns:xsd="http://www.w3.org/2001/XMLSchema#"
xmlns:rdfs="http://www.w3.org/2000/01/rdf-schema#"
xmlns:owl="http://www.w3.org/2002/07/owl#"
xml:base="http://www.owl-ontologies.com/testFood2.owl">
<owl:Ontology rdf:about=""/>
<owl:Class rdf:ID="Cow">
<rdfs:subClassOf>
<owl:Class rdf:ID="RedMeat"/>
</rdfs:subClassOf>
</owl:Class>
<owl:Class rdf:ID="Chicken">
<rdfs:subClassOf>
<owl:Class rdf:ID="WhiteMeat"/>
</rdfs:subClassOf>
</owl:Class>
<owl:Class rdf:ID="Pig2">
<owl:equivalentClass>
<owl:Class rdf:ID="Pig"/>
</owl:equivalentClass>
<rdfs:subClassOf>
<owl:Class rdf:about="#RedMeat"/>
</rdfs:subClassOf>
<rdfs:label rdf:datatype="http://www.w3.org/2001/XMLSchema#string"
>Pig2</rdfs:label>
</owl:Class>
<owl:Class rdf:ID="Onion">
<rdfs:subClassOf>
<owl:Class rdf:ID="Vegetable"/>
</rdfs:subClassOf>
</owl:Class>
<owl:Class rdf:ID="Ingredients"/>
<owl:Class rdf:about="#Pig">
<rdfs:label rdf:datatype="http://www.w3.org/2001/XMLSchema#string"
>Pig</rdfs:label>
<rdfs:subClassOf>
<owl:Class rdf:about="#RedMeat"/>
</rdfs:subClassOf>
<owl:equivalentClass rdf:resource="#Pig2"/>
</owl:Class>
<owl:Class rdf:ID="ChickenWithTomato">
<rdfs:subClassOf>
<owl:Class rdf:ID="Plates"/>
</rdfs:subClassOf>
<rdfs:subClassOf>
<owl:Restriction>
<owl:onProperty>
<owl:ObjectProperty rdf:ID="hasIngridients"/>
</owl:onProperty>
<owl:someValuesFrom>
<owl:Class>
<owl:intersectionOf rdf:parseType="Collection">
<owl:Class rdf:about="#Chicken"/>
<owl:Class rdf:ID="Tomato"/>
</owl:intersectionOf>
</owl:Class>
</owl:someValuesFrom>
</owl:Restriction>
</rdfs:subClassOf>
</owl:Class>
<owl:Class rdf:ID="ChickenWithOnions">
<rdfs:subClassOf rdf:resource="#Plates"/>
<rdfs:subClassOf>
<owl:Restriction>
<owl:onProperty rdf:resource="#hasIngridients"/>
<owl:someValuesFrom>
<owl:Class>
<owl:intersectionOf rdf:parseType="Collection">
<owl:Class rdf:about="#Chicken"/>
<owl:Class rdf:about="#Onion"/>
</owl:intersectionOf>
</owl:Class>
</owl:someValuesFrom>
</owl:Restriction>
</rdfs:subClassOf>
</owl:Class>
<owl:Class rdf:about="#WhiteMeat">
<rdfs:subClassOf>
<owl:Class rdf:ID="Meat"/>
</rdfs:subClassOf>
</owl:Class>
<owl:Class rdf:about="#Tomato">
<rdfs:subClassOf>
<owl:Class rdf:about="#Vegetable"/>
</rdfs:subClassOf>
</owl:Class>
<owl:Class rdf:about="#RedMeat">
<rdfs:subClassOf>
<owl:Class rdf:about="#Meat"/>
</rdfs:subClassOf>
</owl:Class>
<owl:Class rdf:about="#Vegetable">
<rdfs:subClassOf rdf:resource="#Ingredients"/>
</owl:Class>
<owl:Class rdf:about="#Meat">
<rdfs:subClassOf rdf:resource="#Ingredients"/>
</owl:Class>
<owl:ObjectProperty rdf:ID="hasChicken">
<rdfs:subPropertyOf>
<owl:ObjectProperty rdf:ID="hasWhiteMeat"/>
</rdfs:subPropertyOf>
</owl:ObjectProperty>
<owl:ObjectProperty rdf:ID="hasMeat">
<rdfs:subPropertyOf rdf:resource="#hasIngridients"/>
</owl:ObjectProperty>
<owl:ObjectProperty rdf:ID="hasVegetable">
<rdfs:subPropertyOf rdf:resource="#hasIngridients"/>
</owl:ObjectProperty>
<owl:ObjectProperty rdf:ID="hasIngridients_26">
<rdfs:subPropertyOf rdf:resource="#hasIngridients"/>
</owl:ObjectProperty>
<owl:ObjectProperty rdf:ID="hasOnion">
<rdfs:subPropertyOf rdf:resource="#hasVegetable"/>
</owl:ObjectProperty>
<owl:ObjectProperty rdf:about="#hasWhiteMeat">
<rdfs:subPropertyOf rdf:resource="#hasMeat"/>
</owl:ObjectProperty>
</rdf:RDF>
But think that i understand why it cant work that way.
"but I think it's pretty likely that your classes are resources (URIs)"
how i know that?
2009/6/12 Stephane Corlosquet <scorlosquet@gmail.com>
Hi Samuel,
You cannot use ?meatClass owl:Class "Pig" in your WHERE clause
because it is not a valid pattern. You should follow the {subject
property object} pattern in your WHERE clause. owl:Class is a class and
not a property.
Stephane.
On Fri, Jun 12, 2009 at 3:52 PM, Samuel Pedro
<samuelcpspam@gmail.com> wrote:
This is my owl file, i had to add labels to the classes,
and do this:
SELECT ?equivalentClass ?meatClass
WHERE {
?equivalentClass owl:equivalentClass ?meatClass .
?meatClass rdfs:label "Pig" . (in owl file i have Pig
and Pig2)
}
and why this query doesnt work, why it only works for
labels? (I'm trying to understand sparql but...)
SELECT ?equivalentClass ?meatClass
WHERE {
?equivalentClass owl:equivalentClass ?meatClass .
?meatClass owl:Class "Pig" .
}
2009/6/12 Lee Feigenbaum <lee@thefigtrees.net>
Samuel Pedro wrote:
Im trying to do this query...
SELECT ?subject ?object
WHERE { ?subject owl:equivalenteClass
?object FILTER( ?object = "Meat") }
im trying to find the equivalente Class
of meat, but it doesn't return what i want, what am i doing wrong?
if i do this...
SELECT ?subject ?object
WHERE { ?subject owl:equivalenteClass
?object FILTER( ?object != "Meat") }
i get all the equivalent class that
there is in the owl. why?
Without seeing your data, it's hard to say for
sure, but I think it's pretty likely that your classes are resources
(URIs) and "Meat" is just a label for the class. If this is right, you
probably want a query similar to:
SELECT ?equivalentClass ?meatClass
WHERE {
?equivalentClass owl:equivalentClass ?meatClass
..
?meatClass rdfs:label "Meat" .
}
The details will vary depending on what
predicate is used to give a label to your classes (in my example I
assume that it's rdfs:label). Also, note that the label needs to be
exactly "Meat" for this to work.
hope this helps,
Lee
--
--
Samuel Pedro
Received on Friday, 12 June 2009 16:16:54 UTC