Using Grel Slice On a JSON Array Results in an Error

[tobiasschweizer]

Hi there,

I've tried to use the grel:array_slice function (https://users.ugent.be/~bjdmeest/function/grel.ttl#array_slice, https://openrefine.org/docs/manual/grelfunctions#slicea-n-from-n-to-optional) on a JSON input array. It results in an error message:

15:29:02.580 [main] ERROR be.ugent.rml.cli.Main .run(442) - For input string: "one"
java.lang.NumberFormatException: For input string: "one"

I am using RMLMapper 7.3.0.

I would expect the following values to be serialized for schema:name: "two" and "three" (since param_int_i_from is 1 and the first element has the index 0).

Data:

{
  "id": "unique",
  "name": ["one", "two", "three"]
}

Mapping:

@prefix rr: <http://www.w3.org/ns/r2rml#>.
@prefix rml: <http://semweb.mmlab.be/ns/rml#>.
@prefix ql: <http://semweb.mmlab.be/ns/ql#>.
@prefix xsd: <http://www.w3.org/2001/XMLSchema#>.
@prefix schema: <http://schema.org/>.
@prefix wgs84_pos: <http://www.w3.org/2003/01/geo/wgs84_pos#lat>.
@prefix gn: <http://www.geonames.org/ontology#>.
@prefix carml: <http://carml.taxonic.com/carml/> .
@prefix fnml: <http://semweb.mmlab.be/ns/fnml#> .
@prefix grel: <http://users.ugent.be/~bjdmeest/function/grel.ttl#> .
@prefix fno: <https://w3id.org/function/ontology#> .
@base <http://example.com/ns#>.
PREFIX ex: <http://example.org/>

<#LogicalSource> a rml:BaseSource ;
  rml:referenceFormulation ql:JSONPath;
  rml:source "data/test.json" ;
  rml:iterator "$" .

<#AuthorMapping> a rr:TriplesMap ;
  rml:logicalSource <#LogicalSource> ;

  rr:subjectMap [
    rr:template "https://example.com/{id}";
    rr:class schema:Thing
  ] ;

  rr:predicateObjectMap [
    rr:predicate schema:name ;
    rr:objectMap [
      fnml:functionValue <#FunctionValueSlice> ;
    ]
  ] .

<#FunctionValueSlice>
    rr:predicateObjectMap [
           rr:predicate fno:executes ;
           rr:objectMap [ rr:constant grel:array_slice ]
        ] ;

        rr:predicateObjectMap [
            rr:predicate grel:p_array_a ;
            rr:objectMap [
                rml:reference "name" ;
            ]
        ] ;

        rr:predicateObjectMap [
            rr:predicate grel:param_int_i_from ;
            rr:objectMap [
                rr:constant "1"^^xsd:int
            ]
        ] .

        #rr:predicateObjectMap [
        #    rr:predicate grel:param_int_i_opt_to ;
        #    rr:objectMap [
        #        rr:constant "2"^^xsd:int
        #    ]
        #] .

[tobiasschweizer]

@ghsnd I was told you are THE expert. Maybe you can help with this? Thanks!

[ghsnd]

Hi @tobiasschweizer Sorry for the late answer, but the issue should be fixed in the development branch. It was a bug in the underlying library handling functions.

[tobiasschweizer]

Hi @ghsnd No worries, thanks for looking into this. Will this fix be available with the next release?

[DylanVanAssche]

Working on a release as we speak :)

[tobiasschweizer]

now that is fast :-)