2 Ответы Последний ответ: 16.10.2009 19:24, автор: 687900

    comparing SEM_MATCH and SPARQL syntax

      Is there any reference that summarizes the differences between SPARQL syntax and SEM_MATCH in 11gR2? The dev guide talks about SEM_MATCH but I'm hoping there's a consise summary somewhere. Or does SEM_MATCH support full SPARQL syntax now?

        • 1. Re: comparing SEM_MATCH and SPARQL syntax
          There is no summary of differences between SPARQL and SEM_MATCH in the Dev guide, but the main differences are as follows:

          Basically, the graph pattern parameter of SEM_MATCH accepts a SPARQL WHERE clause, including OPTIONAL, FILTER and UNION. However, SEM_MATCH does not support the following "syntactic sugar" graph pattern shorthands.

          1. Predicate-Object Lists


          ?x foaf:name ?name ;
          foaf:mbox ?mbox .

          as shorthand for

          ?x foaf:name ?name .
          ?x foaf:mbox ?mbox .

          2. Object Lists


          ?x foaf:nick "Alice" , "Alice_" .

          as shorthand for

          ?x foaf:nick "Alice" .
          ?x foaf:nick "Alice_" .

          3. RDF Collections


          (1 ?x 3 4) ns1:p "w" .

          as shorthand for

          ?a rdf:first 1 ;
          rdf:rest ?b .
          ?b rdf:first ?x ;
          rdf:rest ?c .
          ?c rdf:first 3 ;
          rdf:rest ?d .
          ?d rdf:first 4 ;
          rdf:rest rdf:nil .
          ?a ns1:p "w" .

          and using

          (1 \[ns1:p ns1:q\] ( 2 ) ) .

          as shorthand for

          ?a rdf:first 1 ;
          rdf:rest ?b .
          ?b rdf:first ?c .
          ?c ns1:p ns1:q .
          ?b rdf:rest ?d .
          ?d rdf:first ?e .
          ?e rdf:first 2 ;
          rdf:rest rdf:nil .
          ?d rdf:rest rdf:nil .

          4. RDF Type


          ?x a :Class1 .

          as shorthand for

          ?x rdf:type :Class1 .

          5. Blank Nodes


          \[ ns1:p "v" \] . or \[\] ns1:p "v" .

          as shorthand for

          _:bnode ns1:p "v" .

          The SPARQL-like syntax of SEM_MATCH also does not support xsd:type constructors. We support the alternative syntax of expressing the RDF term for xsd typed literals.

          For example, we do not support

          FILTER (?x > xsd:float(3.5))

          but we do support the equivalent expression

          FILTER (?x > "3.5"^^xsd:float)
          • 2. Re: comparing SEM_MATCH and SPARQL syntax
            Thanks much for the detailed answer. It helps considerably!