RDF lists created using RDFCollections.asRDF() are not properly serialized using TurtleWriter #3681
Description
Current Behavior
When serializing an RDF list created using RDFCollections.asRDF() with TurtleWriter the first segment of the list is not properly inlined as it is not recognized as a well-formed list.
The result looks as this:
@prefix ex: <http://example.com/ns#> .
@prefix rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#> .
ex:Cities ex:list [ a rdf:List;
rdf:first ex:NewYork;
rdf:rest (ex:Rio ex:Tokyo)
] .
Please notice the first part with explicit rdf:first and rdf:rest statements instead of the inlining of the list, which is done for the last two segments of the list.
This is caused by org.eclipse.rdf4j.rio.turtle.TurtleWriter.isWellFormedCollection() not recognizing the rdf:type rdf:List type statement for the first part of the list segment which is generated in RDFCollections.asRDF() (or more specifically in org.eclipse.rdf4j.model.util.RDFCollections.consumeCollection(Iterable<?>, Resource, Consumer<Statement>, ValueFactory, Resource...)).
A simple solution would be to adjust org.eclipse.rdf4j.rio.turtle.TurtleWriter.isWellFormedCollection() to recognize and accept that statement when checking for additional statements within the list.
Expected Behavior
The proper visualization of the list would instead look like this:
@prefix ex: <http://example.com/ns#> .
@prefix rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#> .
ex:Cities ex:list (ex:NewYork ex:Rio ex:Tokyo) .
Steps To Reproduce
This test case reproduces the behavior:
package com.metaphacts.services.ontologies;
import static org.junit.Assert.assertEquals;
import java.io.StringWriter;
import java.util.List;
import org.eclipse.rdf4j.model.BNode;
import org.eclipse.rdf4j.model.IRI;
import org.eclipse.rdf4j.model.Model;
import org.eclipse.rdf4j.model.impl.TreeModel;
import org.eclipse.rdf4j.model.util.RDFCollections;
import org.eclipse.rdf4j.model.util.Values;
import org.eclipse.rdf4j.model.vocabulary.RDF;
import org.eclipse.rdf4j.rio.RDFFormat;
import org.eclipse.rdf4j.rio.Rio;
import org.eclipse.rdf4j.rio.WriterConfig;
import org.eclipse.rdf4j.rio.helpers.BasicWriterSettings;
import org.junit.Test;
public class RDFCollectionsTest {
@Test
public void testBNodeValuesInList() throws Exception {
final String ns = "http://example.com/ns#";
IRI newyork = Values.iri(ns, "NewYork");
IRI rio = Values.iri(ns, "Rio");
IRI tokyo = Values.iri(ns, "Tokyo");
IRI cities = Values.iri(ns, "Cities");
IRI exList = Values.iri(ns, "list");
BNode listHead = Values.bnode("n1");
Model data = new TreeModel();
data.setNamespace("ex", ns);
data.setNamespace("rdf", RDF.NAMESPACE);
RDFCollections.asRDF(List.of(newyork, rio, tokyo), listHead, data);
data.add(cities, exList, listHead);
String expected = "" +
"@prefix ex: <http://example.com/ns#> .\n" +
"@prefix rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#> .\n" +
"\n" +
"ex:Cities ex:list (ex:NewYork ex:Rio ex:Tokyo) .\n";
StringWriter stringWriter = new StringWriter();
WriterConfig config = new WriterConfig();
config.set(BasicWriterSettings.INLINE_BLANK_NODES, true);
config.set(BasicWriterSettings.PRETTY_PRINT, true);
Rio.write(data, stringWriter, RDFFormat.TURTLE, config);
String actual = stringWriter.toString();
// System.out.println("### ACTUAL ###");
// System.out.println(actual);
// System.out.println("#################\n");
// System.out.println("### EXPECTED ###");
// System.out.println(expected);
// System.out.println("#################\n");
assertEquals("The visual representation should be a proper list for all elements", expected, actual);
}
}
Adding this line before serializing the model as string makes the test work, but the fix should not remove that statement but rather recognize and accept it.
// deleting the type statement in the list would make it work
// [ a rdf:List ]
// data.remove(listHead, RDF.TYPE, RDF.LIST);
Version
3.7.4 (and likely earlier versions as well)
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