SPARQL query universities

Question

I am trying to fetch the names of universities using SPARQL:

The rdf data is the following (and a whole lot more, but that is irrelevant).

<Organization rdf:about="http://data.semanticweb.org/organization/the-university-of-queensland">
    <rdfs:label>The University of Queensland</rdfs:label>
    <homepage rdf:resource="http://www.uq.edu.au/"/>
    <member rdf:resource="http://data.semanticweb.org/person/jane-hunter"/>
    <member rdf:resource="http://data.semanticweb.org/person/kwok-cheung"/>
    <member rdf:resource="http://data.semanticweb.org/person/robert-m-colomb"/>
    <name>The University of Queensland</name>
</Organization>

I have written a java program which queries the data. My string to query the data is the following:

            queryString += "PREFIX swrc:        <http://swrc.ontoware.org/ontology#> \n";
            queryString += "PREFIX dc:          <http://purl.org/dc/elements/1.1/> \n";
            queryString += "PREFIX foaf:        <http://xmlns.com/foaf/0.1/> \n";
            queryString += "PREFIX geo:         <http://www.w3.org/2003/01/geo/wgs84_pos#> \n";
            queryString += "PREFIX ical:        <http://www.w3.org/2002/12/cal/ical#> \n";
            queryString += "PREFIX rdf:         <http://www.w3.org/1999/02/22-rdf-syntax-ns#> \n";
            queryString += "PREFIX rdfs:        <http://www.w3.org/2000/01/rdf-schema#> \n";
            queryString += "PREFIX swc:         <http://data.semanticweb.org/ns/swc/ontology#> \n";
            queryString += "PREFIX swrc_ext:    <http://www.cs.vu.nl/~mcaklein/onto/swrc_ext/2005/05#> \n";
            queryString += "SELECT ?name WHERE {\n";
            queryString += "?university rdfs:label ?aff . \n ?university foaf:name ?name FILTER(str(?aff)='uni') }";

Unfortunately, this is not correct, as no result is returned:

<?xml version='1.0' encoding='UTF-8'?> 
  <sparql xmlns='w3.org/2005/sparql-results#'> 
    <head> 
     <variable name='name'/> 
    </head> 
    <results> 
    </results> 
  </sparql>

Can anyone point me in the right direction?

P.S. If possible I'd like to only fetch 10 university names.

SPARQL allows you to limit the number of results. Just append your query with LIMIT 10. What exactly is wrong with your result? — toniedzwiedz
Thanks for your quick reply. It is supposed to show the names of all universities. Unfortunatelly; this is the result: <?xml version='1.0' encoding='UTF-8'?> <sparql xmlns='w3.org/2005/sparql-results#'> <head> <variable name='name'/> </head> <results> </results> </sparql> — user1390504
I see, so there's no university that matches your criteria. I understand that you're assuming all universities have the string 'uni' in their names. Try replacing FILTER(str(?aff)='uni') with FILTER regex(?aff, "uni", "i") or FILTER regex(str(?aff), "uni", "i"). Still, filtering by name seems like an odd approach to me. Doesn't the data set you're using provide this kind of information as a separate property? It would make sense to classify organizations like this. — toniedzwiedz
I asked myself that question too, by my tutor said there was no such thing available in the assignment, so I'd have to check the stuff like this. — user1390504

toniedzwiedz toniedzwiedz · Accepted Answer · 2012-10-28T14:24:40

I understand that you're assuming all universities have the string "uni" in their names.

Notice that you're checking for equality of a value with the string "uni". There really is no such instance in your data set.

Replacing FILTER(str(?aff)='uni') with FILTER regex(?aff, "uni", "i") will allow you to match the values that contain the string "uni" instead. It's a regular expression filter that takes three arguments.

a variable
a regular expression compliant with the syntax described here
a set of optional flags, in this case, I used one flag, "i". It means the match must be case-insensitive.

In order to limit the number of results, you can just append the query with the LIMIT keyword.

The resulting query should be:

PREFIX swrc:        <http://swrc.ontoware.org/ontology#>
PREFIX dc:          <http://purl.org/dc/elements/1.1/>
PREFIX foaf:        <http://xmlns.com/foaf/0.1/>
PREFIX geo:         <http://www.w3.org/2003/01/geo/wgs84_pos#>
PREFIX ical:        <http://www.w3.org/2002/12/cal/ical#>
PREFIX rdf:         <http://www.w3.org/1999/02/22-rdf-syntax-ns#>
PREFIX rdfs:        <http://www.w3.org/2000/01/rdf-schema#>
PREFIX swc:         <http://data.semanticweb.org/ns/swc/ontology#>
PREFIX swrc_ext:    <http://www.cs.vu.nl/~mcaklein/onto/swrc_ext/2005/05#>
SELECT ?name WHERE {
    ?university rdfs:label ?aff . 
    ?university foaf:name ?name 
    FILTER regex(?aff, "uni", "i")
} LIMIT 10;

SPARQL query universities

2 Answers