RML parsing a CSV which contains XML data.

[paulduchesne]

I have an unusual case, where I am trying to use RML-Mapper to transform a CSV table which contains XML-serialised data in one of the columns.

XML_ID,SCHEMA_TYPE,XML_DATA
1986,32,"<?xml version=""1.0"" encoding=""UTF-8""?>
<Film>
	<Actual_Frames>6</Actual_Frames>
</Film>
"
1994,32,"<?xml version=""1.0"" encoding=""UTF-8""?>
<Film>
	<Actual_Frames>27</Actual_Frames>
</Film>
"

This is my attempt at RML to pull triples from CSV columns, as well as XPath to grab data from the XML data column.

@prefix rr: <http://www.w3.org/ns/r2rml#> .
@prefix rml: <http://semweb.mmlab.be/ns/rml#> .
@prefix rmlxml: <http://semweb.mmlab.be/ns/rml-xml#> .
@prefix ex: <http://example.com/ns#> .
@prefix xsd: <http://www.w3.org/2001/XMLSchema#> .
@prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#> .
@prefix ql: <http://semweb.mmlab.be/ns/ql#> .

ex:testing a rr:TriplesMap;
  rml:logicalSource [
    rml:source "/Users/pduc/Desktop/xml_rml/test.csv";
    rml:referenceFormulation ql:CSV
  ].

ex:testing rr:subjectMap [
  rr:template "https://www.example.com/{XML_ID}"
].

ex:testing rr:predicateObjectMap [
  rr:predicate rdfs:label;
  rr:objectMap [ rml:reference "SCHEMA_TYPE" ]
].

ex:testing rr:predicateObjectMap [
  rr:predicate ex:test_xml;
  rr:objectMap [
    rml:reference "XML_DATA" ;
    rmlxml:referenceFormulation rmlxml:XPath ;
    rmlxml:iterator "/Film/Actual_Frames/text()" ;
  ]
].

This works to some degree, but I am still pulling in the whole XML string, not traversing to pull out a specific field. What I am getting:

@prefix ex: <http://example.com/ns#> .
@prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#> .
@prefix xsd: <http://www.w3.org/2001/XMLSchema#> .

<https://www.example.com/168> ex:test_xml """<?xml version=\"1.0\" encoding=\"UTF-8\"?>
<Film>
	<Actual_Frames>6</Actual_Frames>
</Film>
""";
  rdfs:label "64" .

<https://www.example.com/260> ex:test_xml """<?xml version=\"1.0\" encoding=\"UTF-8\"?>
<Film>
	<Actual_Frames>27</Actual_Frames>

</Film>
""";
  rdfs:label "64" .

And here is what I was hoping to be getting:

@prefix ex: <http://example.com/ns#> .
@prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#> .
@prefix xsd: <http://www.w3.org/2001/XMLSchema#> .

<https://www.example.com/168> ex:test_xml "6";
  rdfs:label "64" .

<https://www.example.com/260> ex:test_xml "27";
  rdfs:label "64" .

What could I be doing wrong?