Examples

The following are examples of the capabilities the R2RML Parser tool offers.

1. Allow arbitrary SQL queries as logical views, using the rr:sqlQuery construct:

   map:dc-creator
   rr:logicalTable <#dc-creator-view>;
   rr:subjectMap [
   rr:template 'http://data.example.com/item/{"item_id"}';
   rr:class dcterms:BibliographicResource;
   ];
   rr:predicateObjectMap [
   rr:predicate dcterms:creator;
   rr:objectMap [ rr:column '"text_value"' ];
   ].
   <#dc-creator-view>
   rr:sqlQuery """
   SELECT i.item_id AS item_id, mv.text_value AS text_value
   FROM item AS i
   INNER JOIN metadatavalue AS mv
   ON i.item_id=mv.item_id
   INNER JOIN metadatafieldregistry AS mfr
   ON mfr.metadata_field_id=mv.metadata_field_id
   INNER JOIN metadataschemaregistry AS msr
   ON msr.metadata_schema_id=mfr.metadata_schema_id
   WHERE i.in_archive=TRUE AND
   mv.text_value IS NOT NULL AND
   msr.namespace='http://dublincore.org/documents/dcmi-terms/' AND
   mfr.element='creator'
   """.
   

2. Allow functions in the SQL queries, for instance string manipulation functions (such as the SQL function replace), which can be nested:

   <#dc-language-view>
   rr:sqlQuery """
   SELECT h.handle AS handle,
   replace(replace(replace(replace(replace(replace(mv.text_value,'Greek','ell'),'Spanish','spa'),'German','deu'),'Italian','ita'),'English','eng'),'French','fra') AS text_value
   FROM handle AS h, item AS i, metadatavalue AS mv, metadataschemaregistry AS msr, metadatafieldregistry AS mfr WHERE
   i.in_archive=TRUE AND
   h.resource_id=i.item_id AND
   h.resource_type_id=2 AND
   msr.metadata_schema_id=mfr.metadata_schema_id AND
   mfr.metadata_field_id=mv.metadata_field_id AND
   mv.text_value is not null AND
   i.item_id=mv.item_id AND
   msr.namespace='http://dublincore.org/documents/dcmi-terms/' AND
   mfr.element='language' AND
   mfr.qualifier IS NULL
   """.
   

3. Allow templates, using rr:template involving many table fields when generating URI's or Literals:

   map:persons
   rr:logicalTable [ rr:tableName '"eperson"'; ];
   rr:subjectMap [
   rr:template 'http://data.example.org/repository/person/{"eperson_id"}';
   rr:class foaf:Person;
   ];
   rr:predicateObjectMap [
   rr:predicate foaf:name;
   rr:objectMap [ rr:template '{"firstname"} {"lastname"}' ;
   rr:termType rr:Literal;
   ]
   ].
   

4. Allow reference to other triple map subjects as objects to a triple map definition, using rr:RefObjectMap. Use of rr:joinCondition, rr:parent and rr:child is optional. In the following example, the objects in the map:TriplesMap1 mapping definition are the subjects in map:TriplesMap2. The rr:joinCondition states that the parent table field Sport.ID values are the ones that also exist in the child table field Student.Sport.

   map:TriplesMap1
   a rr:TriplesMap;
   rr:logicalTable [ rr:tableName  ""Student"" ];
   rr:subjectMap [ rr:template "http://example.com/resource/student_{"ID"}"; ];
   rr:predicateObjectMap
   [
   rr:predicate foaf:name ;
   rr:objectMap [ rr:column ""Name""; ];
   ];
   rr:predicateObjectMap
   [
   rr:predicate http://example.com/ontology/practises ;
   rr:objectMap [
   a rr:RefObjectMap ;
   rr:parentTriplesMap map:TriplesMap2;
   rr:joinCondition [
   rr:child ""Sport"" ;
   rr:parent ""ID"" ; ]
   ];
   ];
   .
   map:TriplesMap2
   a rr:TriplesMap;
   rr:logicalTable [ rr:tableName  ""Sport"" ];
   rr:subjectMap [ rr:template "http://example.com/resource/sport_{"ID"}"; ];
   rr:predicateObjectMap
   [
   rr:predicate rdfs:label ;
   rr:objectMap [ rr:column ""Name""; ];
   ];
   .
   

5. See included example in the iswc folder where you will find:

   • an sql export of a postgres database (iswc-postgres_dump.sql),
   • a mapping file (iswc-mapping_test.rdf), and
   • an rdf dump (iswc-dump.rdf) of the database contents, produced when the mapping file is run against the database.