Dear dpbedia discussion mailing list,
I'm trying to make nice queries to show the power of SPARQL to fellow
researchers. I found it quite hard to get started to drill down to the
correct query format. Let me describe my workflow of constructing my first
query. Maybe you can point out how I could have done better.
First I came up with a question: "List the universities of the Netherlands
in order of establishment".
I used the "select distinct ?Concept where {[] a ?Concept} LIMIT 100" query
at http://dbpedia.org/sparql to get concept names that might help me
construct my query. With CTRL-F I searched for 'University' and found the
concept "http://schema.org/CollegeOrUniversity";.
Next I used: "prefix schema: <http://schema.org/> select distinct ?uni
where {?uni a schema:CollegeOrUniversity}"
I found many USA colleges and universities and went to the dbpedia page of
one of them. There I found the country and established property.
Now I used a Python script with the SPARQLWrapper library to do my next
query (I want to be able to get the output in command line). I ended up
with the following query:
PREFIX dbpedia-owl: <http://dbpedia.org/ontology/>
PREFIX dbpedia: <http://dbpedia.org/resource/>
PREFIX dbpprop: <http://dbpedia.org/property/>
SELECT ?est ?name
WHERE {
?uni a dbpedia-owl:University.
?uni dbpedia-owl:country dbpedia:Netherlands.
?uni dbpprop:nativeName ?name.
?uni dbpprop:established ?est
}
ORDER BY ?est
LIMIT 100
But the results show 3 weird glitches:
1) The "Conservatorium Maastricht" (
http://dbpedia.org/page/Maastricht_Academy_of_Music) has an established
property of 19. I searched for the reason for this weird number and found
that the wikipedia article had 19?? stated as the established date in all
the articles before the 12 October 2011 revision.
My question with this glitch is: Can we add the revision information in the
rdf triples of dbpedia? That makes it easier to find out why a particular
problem occurs and it shows how current the information is.
2) The "Technische Universiteit Eindhoven" (
http://dbpedia.org/page/Eindhoven_University_of_Technology) has an
established property of 23. I think this is due to the fact that this
property is parsed as an xsd:integer, which only works if it only contains
a year of establishment, but we can see on
http://en.wikipedia.org/wiki/Eindhoven_University_of_Technology that an
entire date is given in the infobox. Instead of finding 1956, it uses the
first number it encounters.
3) The "International University in Hospitality Management" (
http://dbpedia.org/page/Hotelschool_The_Hague) has an established property
that seems to be a floating point value. I could not find the cause of this.
Do these problems occur often in dbpedia?
How can I report them properly? Is this the correct place (I cannot access
the bugtracker)?
Is this the 'normal' workflow to construct queries to dbpedia?
Can I suggest to add the 'retrieved_from_revision' relation to the
resources?
Thank you for your time,
Joris Slob, PhD Bioinformatics, Leiden University
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