Conditional instantiation w/ joinCondition not working anymore since v6.3 #236
Description
Environment
rmlmapper v.6.3.0, v6.5.1
Linux/WSL2
Java 11, 17
Namespaces
@prefix owl: <http://www.w3.org/2002/07/owl#> .
@prefix rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#> .
@prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#> .
@prefix xsd: <http://www.w3.org/2001/XMLSchema#> .
@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 ex: <http://data.example.org/resource/> .
@prefix org: <http://www.w3.org/ns/org#> .
@prefix skos: <http://www.w3.org/2004/02/skos/core#> .
@prefix fnml: <http://semweb.mmlab.be/ns/fnml#> .
@prefix fno: <https://w3id.org/function/ontology#> .
@prefix idlab-fn: <http://example.com/idlab/function/> .
Problem
Given the following kind of input XML with relationships between Organization and Address, where the second of three Organizations does not have a StreetName in its Address:
<Directory>
<Organization>
<ID>123</ID>
<Name>ABC FastCo</Name>
<Address>
<StreetName>ABC FastCo Lane</StreetName>
</Address>
</Organization>
<Organization>
<ID>456</ID>
<Name>XYZ Inc.</Name>
<Address>
<Area>XYZ Metro</Area>
</Address>
</Organization>
<Organization>
<ID>789</ID>
<Name>MNO Ltd</Name>
<Address>
<StreetName>99 Maine St</StreetName>
</Address>
</Organization>
</Directory>and the following kind of RML mapping involving a null-default conditional reference on the subjectMap of a joined parentTriplesMap, in order to avoid creating the related Address instance if certain elements (e.g. StreetName) are absent:
ex:Organizations a rr:TriplesMap;
rml:logicalSource [
rml:source "test.xml";
rml:iterator "/Directory/Organization";
rml:referenceFormulation ql:XPath
];
rr:subjectMap [
rr:template "http://data.example.org/resource/Organization_{ID}";
rr:class org:Organization
];
rr:predicateObjectMap [
rr:predicate org:name;
rr:objectMap
[
rml:reference "Name"
];
] ;
rr:predicateObjectMap [
rr:predicate org:address;
rr:objectMap
[
rr:parentTriplesMap ex:Addresses ;
rr:joinCondition [
rr:child "path(.)";
rr:parent "path(..)";
];
];
]
.
ex:Addresses a rr:TriplesMap;
rml:logicalSource [
rml:source "test.xml";
rml:iterator "/Directory/Organization/Address";
rml:referenceFormulation ql:XPath
];
rr:subjectMap [
# rr:template "http://data.example.org/resource/Address_{generate-id(.)}";
rml:reference "if(exists(StreetName)) then 'http://data.example.org/resource/Address_' || generate-id(.) else null";
rr:class org:Address
];
rr:predicateObjectMap [
rr:predicate org:streetName;
rr:objectMap
[
rml:reference "StreetName"
];
] ;
.
Actual
Results in an unexpected null error:
14:49:50.108 [main] ERROR be.ugent.rml.cli.Main .run(420) - Cannot invoke "java.util.Collection.toArray()" because "c" is null
14:49:50.110 [main] ERROR be.ugent.rml.cli.Main .run(457) - Cannot invoke "java.util.Collection.toArray()" because "c" is null
java.lang.NullPointerException: Cannot invoke "java.util.Collection.toArray()" because "c" is null
at java.base/java.util.ArrayList.addAll(ArrayList.java:670)
at be.ugent.rml.Executor.getIRIsWithTrueCondition(Executor.java:464)
at be.ugent.rml.Executor.getIRIsWithConditions(Executor.java:424)
at be.ugent.rml.Executor.generatePredicateObjectGraphs(Executor.java:363)
at be.ugent.rml.Executor.executeWithFunction(Executor.java:178)
at be.ugent.rml.Executor.execute(Executor.java:132)
at be.ugent.rml.cli.Main.run(Main.java:416)
at be.ugent.rml.cli.Main.main(Main.java:49)
Expected
Should result in an output with just two Address instances related by the right Organization instances (and not the third one which fails the condition and therefore would have a null subjectMap leading to no instantiation):
ex:Address_d0e33 a org:Address;
org:streetName "99 Maine St" .
ex:Address_d0e9 a org:Address;
org:streetName "ABC FastCo Lane" .
ex:Organization_123 a org:Organization;
org:address ex:Address_d0e9;
org:name "ABC FastCo" .
ex:Organization_456 a org:Organization;
org:name "XYZ Inc." . # no address relation, correct
ex:Organization_789 a org:Organization;
org:address ex:Address_d0e33;
org:name "MNO Ltd" .
Wrong
If one removes the joinCondition:
rr:objectMap
[
rr:parentTriplesMap ex:Addresses ;
# rr:joinCondition [
# rr:child "path(.)";
# rr:parent "path(..)";
# ];
];
the transformation works, but of course results in erroneous output as the child instances are all related by all parents:
ex:Address_d0e33 a org:Address;
org:streetName "99 Maine St" .
ex:Address_d0e9 a org:Address;
org:streetName "ABC FastCo Lane" .
ex:Organization_123 a org:Organization;
org:address ex:Address_d0e33, ex:Address_d0e9; # wrong
org:name "ABC FastCo" .
ex:Organization_456 a org:Organization;
org:address ex:Address_d0e33, ex:Address_d0e9; # wrong, should have nothing
org:name "XYZ Inc." .
ex:Organization_789 a org:Organization;
org:address ex:Address_d0e33, ex:Address_d0e9; # wrong
org:name "MNO Ltd" .
Workaround
None. Use v6.2.2 or below to get the right result.