On Mon, Apr 19, 2010 at 3:20 PM, Kingsley Idehen <[email protected]>wrote:
> Tom Morris wrote:
> > On Fri, Apr 16, 2010 at 9:23 PM, Kingsley Idehen <[email protected]>
> wrote:
> >
> >> Dan Brickley wrote:
> >>
> >>> On Fri, Apr 16, 2010 at 11:43 PM, Kingsley Idehen
> >>> <[email protected]> wrote:
> >>>
> >>>
> >>>> Tom Morris wrote:
> >>>>
> >>>>
> >>>>> This example query from the DBpedia page returns a list of companies
> >>>>> which all have exactly 151,000 employees:
> >>>>>
> >>>>>
> >>>>>
> http://dbpedia.org/snorql/?query=SELECT+%3Fsubject+%3Femployees+%3Fhomepage+WHERE+{%0D%0A%3Fsubject+rdf:type+%3Chttp://dbpedia.org/class/yago/Company108058098%3E.%0D%0A%3Fsubject+dbpedia2:numEmployees+%3Femployees%0D%0AFILTER+(xsd:integer(%3Femployees)+%3E%3D+50000).%0D%0A%3Fsubject+foaf:homepage+%3Fhomepage.%0D%0A}+ORDER+BY+DESC(xsd:integer(%3Femployees))%0D%0ALIMIT+20%0D%0A
> >>>>>
> >>>>> That seems a rather improbable result. I'm not a real SPARQL guru,
> >>>>> but I don't see anything obviously wrong with the query. Is the
> query
> >>>>> incorrect or is the issue with the database or the server?
> >>>>>
> >>>>> Tom
> >>>>>
> >>>> To save time (i.e. decoding the URL), could you please do the
> following:
> >>>>
> >>>>
> >
> >
> >>>
> >> Problem:
> >>
> >> The Home Page URLs aren't uniform.
> >>
> >> I added DISTINCT and removed ?homepage.
> >>
> >> So not a bug :-)
> >>
> >> Try
> >>
> >> PREFIX owl: <http://www.w3.org/2002/07/owl#>
> >> PREFIX xsd: <http://www.w3.org/2001/XMLSchema#>
> >> PREFIX rdfs: <http://www.w3.org/2000/01/rdf-schema#>
> >> PREFIX rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#>
> >> PREFIX foaf: <http://xmlns.com/foaf/0.1/>
> >> PREFIX dc: <http://purl.org/dc/elements/1.1/>
> >> PREFIX : <http://dbpedia.org/resource/>
> >> PREFIX dbpedia2: <http://dbpedia.org/property/>
> >> PREFIX dbpedia: <http://dbpedia.org/>
> >> PREFIX skos: <http://www.w3.org/2004/02/skos/core#>
> >>
> >> SELECT distinct ?subject ?employees WHERE {
> >> ?subject rdf:type <http://dbpedia.org/class/yago/Company108058098>.
> >> ?subject dbpedia2:numEmployees ?employees
> >> FILTER (xsd:integer(?employees) >= 50000).
> >> ?subject foaf:homepage ?homepage.
> >> } ORDER BY DESC(xsd:integer(?employees))
> >> LIMIT 20
> >>
> >> Links:
> >>
> >> 1. http://bit.ly/byXSGf -- SPARQL Protocol URL
> >>
> >
> > Thanks! That did the trick. It looks like the DISTINCT keyword was
> > the main issue since it also seems to work with the homepages included
> > as long as the DISTINCT keyword is there.
> >
> > Hopefully one of the DBpedians will see this and update the example at
> > http://wiki.dbpedia.org/Datasets#h18-12. (The other two example
> > queries in that section seem to work as expected).
> >
> > Tom
> >
> >
> Ted,
>
> Please update the Wiki page accordingly.
>
>
> --
>
> Regards,
>
> Kingsley Idehen
> President & CEO
> OpenLink Software
> Web: http://www.openlinksw.com
> Weblog: http://www.openlinksw.com/blog/~kidehen
> Twitter/Identi.ca: kidehen
>
>
Forgive an innocent bystander a little confusion, but I'm not sure I
understand what's going on with this query. I've taken out the foaf:homepage
term, as you suggested (though I'm not sure what you meant by "aren't
uniform"), and have fiddled with the rest of the query; it seems like
there's an odd interaction between ORDER BY (xsd:integer(...)) and
FILTER(xsd:integer(...)).
For example, the query
SELECT ?subject ?employees WHERE {
?subject rdf:type <http://dbpedia.org/class/yago/Company108058098>;
dbpedia2:numEmployees ?employees.
FILTER (xsd:integer(?employees) >= 50000).
} ORDER BY DESC(xsd:integer(?employees))
LIMIT 20
returns a set of results, all with the same number of employees. If I change
that LIMIT to (say) 30, it changes the number of employees for *all* the
result bindings - and they're all still the same value as each other.
If you discard one of either the FILTER or the ORDER BY, the results seem
normal. If you change it to SELECT DISTINCT, the results seem normal.
However, the problem isn't with duplicate result rows, so the DISTINCT
shouldn't be changing the values for a single binding, should it?
I'll be the first to admit my SPARQL is a little hazy, so I might be
forgetting some nuance of the spec here...I just can't seem to figure it out
:-) As I say, I'm just a bystander in this conversation, too, so don't
expend too much effort if I seem to be heading off into the weeds somewhere!
Cheers,
Peter
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