I am using protege for creating an ontology, actually I downloaded an existence ontology and add some subclasses and individuals in it. now I try to set a prefix for that in this shape:
PREFIX food:
it is the original ontology not that I changed so it didnt work. how can I set PREFIX from my local computer? is it possible or I should upload it somewhere?
second I want to query in protege using SPARQL tab in it, I want to 1) get individuals of a class 2) get direct class of an individual. I mean his first parent not in hierarchy. I try it with rdf:type it dident work(maybe bcz of false PREFIX!) any idea for getting individual and class of another individual? thanks in advance
Hi Saba,
I downloaded food RDF ontology from www.w3.org and I'm using Protege 3.4.5. However, I changed the file extension from food.rdf to food.owl so I can easily loaded it Protege as a new project.
All individuals of a specific class vin:Winery:
SELECT ?x
WHERE { ?x rdf:type vin:Winery}
Facts in the ontology - individuals, classes, relationships (i.e. TBox and ABox):
SELECT distinct ?ind ?class
WHERE { ?ind rdf:type ?class }
ORDER BY ?class
...or even better:
SELECT *
WHERE {
?ind rdf:type ?type .
OPTIONAL { ?type rdfs:subClassOf ?class }
}
ORDER BY ?class
I did not specify prefix. The SPARQL code here is direct copy-paste from Protege.
Remember that prefix is a logical unique identifier. All ontologies have to be successfully imported (loaded) in the same project and the prefix is only used to distinguish between them. It is not uncommon to use several separate ontologies at once and they share same labels for different things so prefixes become necessary. In this working environment (Protege 3.4.5 + SPARQL Query Panel) there is no "loading ontologies in run time" when you run a query. TBox and ABox have to be set up before querying.
If you have more questions about getting individuals of classes I suggest you take a look at semanticweb.org (http://answers.semanticweb.com/questions/2443/find-classes-with-sparql) and stackoverflow.com (http://stackoverflow.com/questions/18666574/sparql-query-to-retrieve-individuals-of-a-class). A short tutorial on Protege imports: http://pmc.ucsc.edu/~dmk/notes/Protege+OWL+Imports.html.
Also, on the web there are several nice tutorials on SPARQL with examples such as:
- http://jena.apache.org/tutorials/sparql.html
- http://www.cambridgesemantics.com/semantic-university/sparql-by-example
- http://www.linkeddatatools.com/querying-semantic-data
- https://code.google.com/p/tdwg-rdf/wiki/Beginners6SPARQL
- http://www.ibm.com/developerworks/library/j-sparql/
- http://logd.tw.rpi.edu/tutorial/a_crash_course_on_sparql
- ...
I hope this helps,
Marko
Dear Saba. I have the exact same quesition (Having a class ?class, how do I get all the individuals beloging to this class). How did you find a solution to this? The answers given to you by M. Hamiz and Marco Horvat are not satisfactory for me, because as far as I understand their queries only retrieve
A) the direct members of a class (i.e. indivuals asserted in the A-Box via the rdf:type to a class)
B) the members of a **direct subclass** of class ?class, this is what I read from OPTIONAL { ?type rdfs:subClassOf ?class }
But what if there is a deeper hierarchy (let's say ?class has a subclass and this subclass has another subclass)
Best regards,
Sabina
Hello Saba, at the end of the PREFIX URL before the closing > tag add this #, was it useful left me know thanks
For the prefixes, look in the Active Ontology tab at the bottom. There is a sub tab at the bottom called Ontology Prefixes. You can see all the prefixes that currently exist there and you can add new ones if you want, or you can copy and paste ones that you need into the SPARQL query window. See the screen snapshot I've attached.
Regarding the issue of retrieving classes in SPARQL as others have pointed out SPARQL (unlike the DL Query window or writing rules in SWRL) will only retrieve direct instances of classes not instances of superclasses. So if all you want is a query you can use the DL Query window and type the name of your class in the query field. Make sure the Instances check box on the right is checked. That should give you all the instances of a class and its subclasses.
For SPARQL, at least with Protege, one option is to explicitly match for the instances of the subclasses. If you do that you should probably put them in an OPTIONAL expression, otherwise if you query for instances of more than one class you will of course only get matches for objects that are instances of every class, rather than instances say that are only instances of the highest superclass.
A SPARQL option that IMO is better though is to use the "File>Export inferred axioms as ontology" option. There is a minor bug in that command on some platforms so I wrote a short blog article on it: https://www.michaeldebellis.com/post/export-inferred-axioms If you use this command then all of the reasoner inferences will be saved as if they are user defined axioms and your individuals will be direct instances of every class so that SPARQL will recognize the reasoner inferences. This is useful for a number of other tools in Protege as well.
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