🐛 - Error in the definition of "rml:reference"

[Jhon Toledo]

Mapping: gtfs-csv-noselfjoin.yml

Result:

  rr:objectMap [
          a rr:ObjectMap;
          rml:reference http://transport.linkeddata.es/resource/PickupType/"pickup_type"~iri
  ]

chek the specification: https://rml.io/specs/rml/#reference

[LuisLopezPi]

I think now works as intended

[Jhon Toledo]

In my example(CSV) this is the result:

rr:predicateObjectMap [
                a rr:PredicateObjectMap;
                rr:predicate a;
                rr:objectMap [
                        a rr:ObjectMap;
                        rml:reference gtfs:Agency       <----------------------- ERROR HERE
                ]
        ];

rml:reference is used to refer to:

• a column in case of databases,
• a record in case of CSV or TSV data source

If you need to refer http://vocab.gtfs.org/terms#Agency I think the best way is rr:rr:constant

        rr:predicateObjectMap [
                a rr:PredicateObjectMap;
                rr:predicate rdf:type;
                rr:objectMap [
                        a rr:ObjectMap;
                        rr:constant gtfs:Agency;
                ]
        ];

My yarrrml example:

prefixes:
  rr: http://www.w3.org/ns/r2rml#
  foaf: http://xmlns.com/foaf/0.1/
  xsd: http://www.w3.org/2001/XMLSchema#
  rdfs: http://www.w3.org/2000/01/rdf-schema#
  dc: http://purl.org/dc/elements/1.1/
  rev: http://purl.org/stuff/rev#
  gtfs: http://vocab.gtfs.org/terms#
  geo: http://www.w3.org/2003/01/geo/wgs84_pos#
  schema: http://schema.org/
  dct: http://purl.org/dc/terms/
  rml: http://semweb.mmlab.be/ns/rml#
  ql: http://semweb.mmlab.be/ns/ql#
  rdf: http://www.w3.org/1999/02/22-rdf-syntax-ns#

mappings:
   agency:
    sources:
      - [/data/csv/1/AGENCY.csv~csv]
    s: http://transport.linkeddata.es/madrid/agency/$(agency_id)
    po:
      - [a, gtfs:Agency]
      - [foaf:page, $(agency_url)~iri]
      - [foaf:name,$(agency_name)]
      

[LuisLopezPi]

so, when the object is gtfs, should I use constant instead of reference?

[David Chaves]

reference is when you have $(XXX), template when string+$(XXXX) in any order, and constant is when the object does not have any reference to the source (i.e., no $(XXX))

[David Chaves]

notice that reference, constant and template can be in subjectMap, predicateMap and objectMap

[LuisLopezPi]

Fixed! now detects diferents termMaps