RML conditional mapping using custom functions.

[nayomirana]

Hi,
I have the following data in a test.csv file, which contains information about organization details.

If the Address field is not null, I need to establish a relationship between the Name and Email entities using the predicate "hasContactDetails". I attempted the following code but was unable to achieve the desired outcome. The function isNotNullCustom is a custom Java function that returns true if the value is not null. I’m using java-rml mapper.

@Prefix rr: http://www.w3.org/ns/r2rml# .
@Prefix rml: http://semweb.mmlab.be/ns/rml# .
@Prefix csvw: http://www.w3.org/ns/csvw# .
@Prefix fnml: http://semweb.mmlab.be/ns/fnml# .
@Prefix fno: https://w3id.org/function/ontology# .
@Prefix grelf: http://users.ugent.be/~bjdmeest/function/grel.ttl# .
@Prefix grelm: http://fno.io/grel/rmlmapping# .
@Prefix fns: http://example.com/fns# .
@Prefix xsd: http://www.w3.org/2001/XMLSchema# .
@Prefix rdfs: http://www.w3.org/2000/01/rdf-schema# .
@Prefix myVocab: http://example.org/ns/myVocab# .
@Prefix ql: http://semweb.mmlab.be/ns/ql# .
@Prefix ex: http://example.org/ .
@base http://example.com/ .

<#LogicalSource> a rr:TriplesMap ;
  rml:logicalSource [
    rml:source "test.csv" ;
    rml:referenceFormulation ql:CSV ;
    rml:csvw:delimiter ","
  ];

 rr:subjectMap [
    rr:template "http://example.com/Organization/{ID}" ;
    rr:class myVocab:Organization
  ];

  rr:predicateObjectMap [
    rr:predicate myVocab:name;
    rr:objectMap [
      rml:reference "Name";
      rr:datatype xsd:string
    ]
  ];

 rr:predicateObjectMap [
    rr:predicate myVocab:hasContactDetails;
    rr:objectMap [
      fnml:functionValue [
        rr:predicateObjectMap [
            rr:predicate fno:executes ;
            rr:objectMap [ rr:constant grelf:controls_if ] ] ;
        rr:predicateObjectMap [
            rr:predicate grelf:valueParameter ;
            rr:objectMap [
                fnml:functionValue [
                    rr:predicateObjectMap [
                        rr:predicate fno:executes ;
                        rr:objectMap [ rr:constant ex:isNotNullCustom ] ] ;
                    rr:predicateObjectMap [
                        rr:predicate grelf:valueParameter ;
                        rr:objectMap [ rml:reference "Address" ] ]
                ]
            ] ;
        ];
        rr:predicateObjectMap [
            rr:predicate grelf:any_tru ;
            rr:objectMap [ rml:reference "Email" ] ]
      ]
    ]
  ].

I am receiving the following error.

16:23:28.490 [main] ERROR be.ugent.rml.cli.Main               .run(423) - Function with id http://users.ugent.be/~bjdmeest/function/grel.ttl#controls_if not found
16:23:28.493 [main] ERROR be.ugent.rml.cli.Main               .run(458) - Function with id http://users.ugent.be/~bjdmeest/function/grel.ttl#controls_if not found
be.ugent.idlab.knows.functions.agent.functionModelProvider.fno.exception.FunctionNotFoundException: Function with id http://users.ugent.be/~bjdmeest/function/grel.ttl#controls_if not found
        at be.ugent.idlab.knows.functions.agent.AgentImpl.execute(AgentImpl.java:78)
        at be.ugent.idlab.knows.functions.agent.AgentImpl.execute(AgentImpl.java:54)
        at be.ugent.rml.functions.DynamicMultipleRecordsFunctionExecutor.execute(DynamicMultipleRecordsFunctionExecutor.java:85)
        at be.ugent.rml.functions.AbstractSingleRecordFunctionExecutor.execute(AbstractSingleRecordFunctionExecutor.java:16)
        at be.ugent.rml.termgenerator.LiteralGenerator.generate(LiteralGenerator.java:47)
        at be.ugent.rml.Executor.generatePredicateObjectsForSubjects(Executor.java:492)
        at be.ugent.rml.Executor.executeWithFunction(Executor.java:172)
        at be.ugent.rml.Executor.execute(Executor.java:152)
        at be.ugent.rml.cli.Main.run(Main.java:421)
        at be.ugent.rml.cli.Main.main(Main.java:47)
be.ugent.idlab.knows.functions.agent.functionModelProvider.fno.exception.FunctionNotFoundException: Function with id http://users.ugent.be/~bjdmeest/function/grel.ttl#controls_if not found

Thank You..

[dachafra]

Maybe @bjdmeest can answer this question

[bjdmeest]

The issue is actually that, when you load your custom functions (using the -f directive in the RMLMapper CLI), the original GREL functions are no longer loaded (to make sure no conflicts arise). So if you add your own function and also want to load the grel functions, make sure to also add the references to the grel functions (available at https://github.com/RMLio/rmlmapper-java/blob/72c6a636d7f7bd9e09dc0028f2ccb7b26b76c32e/src/main/resources/functions_grel.ttl and https://github.com/FnOio/grel-functions-java/blob/master/src/main/resources/grel_java_mapping.ttl). Typing this, I have the feeling it makes more sense to keep them loaded by default. I made an issue at RMLio/rmlmapper-java#244

[nayomirana]

Thank you