[GitHub] [jena] kinow commented on issue #725: JENA-1881: RDF*

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kinow commented on issue #725: JENA-1881: RDF*
URL: https://github.com/apache/jena/pull/725#issuecomment-614389607
 
 
   Running Fuseki on this branch now. @afs , my SPARQL-Fu is quite rusty, so could you help me with a simple test query?
   
   I'm using the `books.ttl` shipped with Jena source code. After reading the paper (at least the abstract and intro, without delving into the details), I came up with a query that I think should be use reification.
   
   ```sparql
   prefix purl: <http://purl.org/dc/elements/1.1/>
   prefix vcard: <http://www.w3.org/2001/vcard-rdf/3.0#>
   prefix dc: <http://purl.org/dc/elements/1.1/>
   prefix : <http://example.org/book/>
   
   SELECT ?authorFamilyName ?bookName
   WHERE {
     ?book dc:title ?bookName ;
           dc:creator ?author .
     ?author vcard:N ?authorName .
     ?authorName vcard:Family ?authorFamilyName .          
   }
   LIMIT 25
   ```
   
   Then my plan was to replace the reification by RDF*. But Fuseki is failing the following query with "[2020-04-16 15:02:57] Fuseki     WARN  [34] RC = 500 : Attempt to hash something strange: << ?book @dc:creator ?author >>".
   
   ```sparql
   prefix purl: <http://purl.org/dc/elements/1.1/>
   prefix vcard: <http://www.w3.org/2001/vcard-rdf/3.0#>
   prefix dc: <http://purl.org/dc/elements/1.1/>
   prefix : <http://example.org/book/>
   
   SELECT ?authorFamilyName ?bookName
   WHERE {
     ?book dc:title ?bookName .
     <<?book dc:creator ?author>> vcard:N ?authorName .
     ?authorName vcard:Family ?authorFamilyName .          
   }
   LIMIT 25
   ```

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