RMLio/yarrrml-parser

How to represent one-to-many and nested relationships

qzc438 opened this issue · 6 comments

qzc438 commented

Issue type: ❓ Question

As shown in the excel query-result.csv, I am asking how to represent one-to-many and nested relationships:

  1. AHU1A has two sub-equipment VAV2-3 and VAV2-4.
  2. VAV2-4 has one sensor VAV2-4.DPR and this sensor have a sub-sensor VAV2-4.DPRPOS.
bjdmeest commented

See the example YARRRML below, does this answer your question?

prefixes:
  ex: "http://example.com/"
  idlab-fn: "http://example.com/idlab/function/"
  grel: "http://users.ugent.be/~bjdmeest/function/grel.ttl#"

mappings:
  Equipment:
    sources:
      - ['data.csv~csv']
    s: http://example.com/equiment/$(Equipment)
    po:
      - [a, ex:Equipment]
      - [ex:subEquipment, http://example.com/equiment/$(Sub-Equipment)~iri]
      - [ex:hasSensor, http://example.com/sensor/$(Sensor)~iri]
  Sensor:
    sources:
      - ['data.csv~csv']
    s: http://example.com/sensor/$(Sensor)
    po:
      - [a, ex:Sensor]
      - [ex:subSensor, http://example.com/sensor/$(Sub-Sensor)~iri]
qzc438 commented

Can I know how to deal with the blank nodes in the sample query-result.csv?

bjdmeest commented

How do you mean? Empty values are by default seen as null values and thus skipped, conforming to the R2RML specification. Have you been able to try the example given above? In what way does its output not conform with your expectations?

qzc438 commented

If you look at Line 2 and 3 in my CSV, AHU1A appears twice because it links to VAV-3 and VAV4. Will it occur as a duplicate definition in [a, ex:Equipment]?

bjdmeest commented

The resulting graph might contain duplicates, but mapping engines could filter out duplicates, see eg https://github.com/RMLio/rmlmapper-java#duplicate-removal-and-serialization-format.

qzc438 commented