Re: [dotNetRDF-Support] typed literals

[Mark D W. <mar...@ko...>]

Hi Rob,

Thanks for the reply.

The tuples are getting loaded to the same graph against which the query is being executed; I verified that by querying for all tuples.

After reading the interesting article “RDF Literal Types in Practice” [1] I thought to try the following:

PREFIX me: <http://www.example.com/>
PREFIX xsd: <http://www.w3.org/2001/XMLSchema#>
SELECT DISTINCT ?s ?p WHERE {
  ?s ?p ?o .
  FILTER (xsd:integer(?o) = 42)
}

which in fact does work.

Somehow the pattern matching doesn’t match, though.

-Mark




[1] http://iswc2011.semanticweb.org/fileadmin/iswc/Papers/Workshops/SSWS/Emmons-et-all-SSWS2011.pdf


From: Rob Vesse [mailto:rv...@do...]
Sent: Monday, December 15, 2014 7:05 AM
To: dotNetRDF User Help and Support
Subject: Re: [dotNetRDF-Support] typed literals

Mark

You've likely run into the fact that when you've loaded your graph the library automatically assigned it a name so then when you ran your query it only considered the default graph which was empty rather than your named graph which contained the actual data.

https://bitbucket.org/dotnetrdf/dotnetrdf/wiki/UserGuide/Querying%20with%20SPARQL#!default-graph

You likely just need to make sure that your loaded graph is actually the default graph which you can do in several ways, the easiest of which (assuming you have only a single graph) is simply to set the BaseUri property to null after loading your data so that the graph is treated as the default graph when you add it to a store ready for querying.

Rob

From: Mark D Wood <mar...@ko...<mailto:mar...@ko...>>
Reply-To: dotNetRDF User Help and Support <dot...@li...<mailto:dot...@li...>>
Date: Friday, 12 December 2014 20:50
To: "dot...@li...<mailto:dot...@li...>" <dot...@li...<mailto:dot...@li...>>
Subject: [dotNetRDF-Support] typed literals

I’m noticing some anomalies in the handling of typed literals

Here’s a very simple RDF/XML file, with just two statements.  The first has a literal with an integer typed value of 42.

<?xml version="1.0" encoding="utf-8"?>
<rdf:RDF xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#<http://www.w3.org/1999/02/22-rdf-syntax-ns>" xmlns:dc="http://purl.org/dc/elements/1.1/"  xml:base="http://www.w3.org/2001/XMLSchema#<http://www.w3.org/2001/XMLSchema>" xmlns:me="http://www.example.com/"<http://www.example.com/%22>>
<rdf:Description rdf:about="urn:guid:00000000-0000-0000-0000-000000000003" >
               <me:A rdf:datatype="http://www.w3.org/2001/XMLSchema#integer">42</me:A>
               <me:B rdf:datatype="integer">37</me:B>
</rdf:Description>
</rdf:RDF>

If I execute the following query,

PREFIX me: <http://www.example.com/>
PREFIX xsd: <http://www.w3.org/2001/XMLSchema#<http://www.w3.org/2001/XMLSchema>>
SELECT DISTINCT ?s ?p WHERE {
  ?s ?p 42 .
}
LIMIT 25

the two external triplestore implementations I tried correctly return one tuple; however, the dotNetRDF LeviathanQueryProcessor using the in-memory store does not return any tuples.  Is this a bug, or operator error?

Also, I was hoping to reduce the size of my RDF/XML by using the xml:base construct, but I don’t seem to be able to get the xml:base attribute to take effect.  Is there a trick to getting that to work?

Thanks,
-Mark

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