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AW: Sparql query help

From: Dau, Frithjof <frithjof.dau@sap.com>
Date: Fri, 12 Jun 2009 17:51:23 +0200
Message-ID: <EDFFA9D51148B34FAA0B828A82AAE70C022B9593@dewdfe1g.wdf.sap.corp>
To: "Samuel Pedro" <samuelcpspam@gmail.com>, "Stephane Corlosquet" <scorlosquet@gmail.com>, "Lee Feigenbaum" <lee@thefigtrees.net>, <public-sparql-dev@w3.org>
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 GMT

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