No results when running a SPARQL on an rdf document

I'm new to SPARQL querys and I'm using twinkle SPARQL to run a query on an rdf document that contians:

<defaultNamespac:courses rdf:ID="Cources">   
  <defaultNamespac:course rdf:resource="#Course1"/>
  <defaultNamespac:course rdf:resou开发者_如何学Crce="#Course10"/>
  <defaultNamespac:course rdf:resource="#Course2"/>
  <defaultNamespac:course rdf:resource="#Course3"/>
  <defaultNamespac:course rdf:resource="#Course4"/>
  <defaultNamespac:course rdf:resource="#Course5"/>
  <defaultNamespac:course rdf:resource="#Course6"/>
  <defaultNamespac:course rdf:resource="#Course7"/>
  <defaultNamespac:course rdf:resource="#Course8"/>
  <defaultNamespac:course rdf:resource="#Course9"/>
</defaultNamespac:courses>

The Query is as follows:

SELECT ?x ?course

WHERE {?x <file:/F:/Stuff/Muaz/GUC/Met.rdf#courses> ?course }

the problem is that no results are returned (only the x and course is displayed). Whats wrong? I'm getting on my nervous, Please help me as soon as you can. Thank you very much!

PS: What datatypes can be returned by the query? (only strings or numbers ?!)

Just a quick guess Is it defaultNamespac or defaultNamespace ? witn an e at the end.

If that is not the error try to run the query:

SELECT * WHERE { ?s ?p ?o }

If I had the following RDF file, with some defaultNamepac define :

<rdf:RDF
   xmlns:contact="http://www.w3.org/2000/10/swap/pim/contact#"
   xmlns:defaultNamespac="http://foo.bar"
   xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#">
  <defaultNamespac:courses rdf:about="file:///Users/msalvadores/kk.rdf#Cources">
    <defaultNamespac:course rdf:resource="file:///Users/msalvadores/kk.rdf#Course1"/>
    <defaultNamespac:course rdf:resource="file:///Users/msalvadores/kk.rdf#Course10"/>
    <defaultNamespac:course rdf:resource="file:///Users/msalvadores/kk.rdf#Course2"/>
    <defaultNamespac:course rdf:resource="file:///Users/msalvadores/kk.rdf#Course3"/>
    <defaultNamespac:course rdf:resource="file:///Users/msalvadores/kk.rdf#Course4"/>
    <defaultNamespac:course rdf:resource="file:///Users/msalvadores/kk.rdf#Course5"/>
    <defaultNamespac:course rdf:resource="file:///Users/msalvadores/kk.rdf#Course6"/>
    <defaultNamespac:course rdf:resource="file:///Users/msalvadores/kk.rdf#Course7"/>
    <defaultNamespac:course rdf:resource="file:///Users/msalvadores/kk.rdf#Course8"/>
    <defaultNamespac:course rdf:resource="file:///Users/msalvadores/kk.rdf#Course9"/>
  </defaultNamespac:courses>
</rdf:RDF>

Then the result of the above query would be, like the image shows:

In my case wih namespace xmlns:defaultNamespac="http://foo.bar" if I wanted to run exactly your query then I'd had to use the namespace ...

SELECT ?x ?course

WHERE {?x <http://foo.bar#courses> ?course }

My advice is that to avoid these errors try always to set namespaces.