RDFXML: possible to load incorrect XML

[sszuev]

RDFXML: possible to load incorrect XML

[afs]

There are a lot of warnings.

But it parses for me using riot for both Jena 4.10.0 and Jena 5.1.0 - different RDF though.
RDF/XML documents don't have to have a rdf:RDF.

Would it be possible to have more concise examples of problems? It should only need a short example.

[sszuev]

What about this ?

String data = """
        <?xml version="1.0"?>
        <Ontology xmlns="http://www.w3.org/2002/07/owl#"
             xml:base="http://www.w3.org/2002/07/owl#"
             xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
             xmlns:xml="http://www.w3.org/XML/1998/namespace"
             xmlns:xsd="http://www.w3.org/2001/XMLSchema#"
             xmlns:rdfs="http://www.w3.org/2000/01/rdf-schema#">
            <Prefix name="owl" IRI="http://www.w3.org/2002/07/owl#"/>
            <Prefix name="rdf" IRI="http://www.w3.org/1999/02/22-rdf-syntax-ns#"/>
            <Prefix name="xml" IRI="http://www.w3.org/XML/1998/namespace"/>
            <Prefix name="xsd" IRI="http://www.w3.org/2001/XMLSchema#"/>
            <Prefix name="rdfs" IRI="http://www.w3.org/2000/01/rdf-schema#"/>
            <Declaration>
                <Class IRI="http://x#X"/>
            </Declaration>
        </Ontology>
        """;
ModelFactory.createDefaultModel()
        .read(new StringReader(data), null, "rdf/xml")
        .setNsPrefixes(PrefixMapping.Standard).write(System.out, "ttl");

output

PREFIX dc:   <http://purl.org/dc/elements/1.1/>
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#>

[ rdf:type         owl:Ontology;
  owl:Declaration  [ rdf:type  owl:Class ];
  owl:Prefix       ""
] .

To create such a document, OWLAPI or owlcs/ONTAPI can be used:

OWLOntologyManager m = OntManagers.createOWLAPIImplManager();
OWLOntology ont = m.createOntology();
ont.add(m.getOWLDataFactory().getOWLDeclarationAxiom(m.getOWLDataFactory().getOWLClass(IRI.create("http://x#X"))));
ont.saveOntology(new OWLXMLDocumentFormat(), System.out);

[afs]

I can't make Jena4 cause an error parsing; it does throw an exception when writing the model due to a relative IRI for a property.

Jena4 parsing issues warnings, as does Jena5.

There is a difference output between Jena4 and Jena5.

<?xml version="1.0"?>

<Ontology xmlns:p="http://example/ns#">
  <Prefix p:name="rdf"/>
</Ontology>

with p:name - no warnings. If the XML attribute is name= (no namespace) there is a warning.

In Jena4, ARP issues a warning and outputs a relative URI property. It also generate an relative URI for Ontology.

In Jena5, RRX issues a warning and skips the triple. It resolves the Ontology against the base (and there is always a base which may be external).

This is by design. In writing RRX, I checked all the cases ARP supports. It was decided by the RDF 1.0 WG that bare attributes were not legal - they had been in the earlier design phases but that never made it to a spec. So in RRX it a warning and skipping, it is not a hard error due to legacy with ARP. Relative URIs will get into trouble later!

I'd be happy for that to become a error, not warning.

The fact that the doc parses as RDF/XML at all is because the root qname does not have to be rdf:RDF, for a single top-level element, that can be omitted. This is the case Jena4 and Jena5, in ARP and RRX.

ARP (0 - the original; 1 - more integrated into RIOT error handling) is available in Jena5, at the moment, as lang name "arp0", "arp1" or as a file extension, and deprecated constant RRX.RDFXML_ARP0

Expect ARP0 to go away soon.

ARP1 was the RDF/XML parser from started in 4.7.0 to 4.10.0,

[afs]

As the distingushing RDF/XML from OWL/XML, it hard/impossible in the most general case. It would be better to read the input, snoop for the top level element and decide then reparse (all after checking MIME type and file extension if available).

File extension owl was never registered and in the wild, you can find owl for RDF/XML.

[sszuev]

I can't make Jena4 cause an error parsing; it does throw an exception when writing the model due to a relative IRI for a property.

It seems need to use the original ontology document https://github.com/owlcs/ont-api/blob/4.x.x/src/test/resources/owlapi/owlxml_anonloop.owx

[afs]

What's the error message, and is there a small extract that picks up the feature in error?

[sszuev]

<?xml version="1.0"?>
<Ontology xmlns="http://www.w3.org/2002/07/owl#"
     xml:base="http://www.derivo.de/ontologies/examples/anonymous-individuals"
     xmlns:rdfs="http://www.w3.org/2000/01/rdf-schema#"
     xmlns:xsd="http://www.w3.org/2001/XMLSchema#"
     xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
     xmlns:xml="http://www.w3.org/XML/1998/namespace"
     ontologyIRI="http://www.derivo.de/ontologies/examples/anonymous-individuals">
    <Prefix name="" IRI="http://www.derivo.de/ontologies/examples/anonymous-individuals#"/>
    <Prefix name="owl" IRI="http://www.w3.org/2002/07/owl#"/>
    <Prefix name="rdf" IRI="http://www.w3.org/1999/02/22-rdf-syntax-ns#"/>
    <Prefix name="xsd" IRI="http://www.w3.org/2001/XMLSchema#"/>
    <Prefix name="rdfs" IRI="http://www.w3.org/2000/01/rdf-schema#"/>
    <ClassAssertion>
        <Class IRI="#C"/>
        <AnonymousIndividual nodeID="a"/>
    </ClassAssertion>
</Ontology>

Exception in thread "main" org.apache.jena.riot.RiotException: [line: 16, col: 42] {E201} Multiple children of property element
	at org.apache.jena.riot.system.ErrorHandlerFactory$ErrorHandlerStd.error(ErrorHandlerFactory.java:160)
	at org.apache.jena.riot.lang.ReaderRIOTRDFXML$ErrorHandlerBridge.error(ReaderRIOTRDFXML.java:292)
	at org.apache.jena.rdfxml.xmlinput.impl.ARPSaxErrorHandler.error(ARPSaxErrorHandler.java:37)
	at org.apache.jena.rdfxml.xmlinput.impl.XMLHandler.warning(XMLHandler.java:206)
	at org.apache.jena.rdfxml.xmlinput.impl.XMLHandler.warning(XMLHandler.java:183)
	at org.apache.jena.rdfxml.xmlinput.impl.XMLHandler.warning(XMLHandler.java:178)
	at org.apache.jena.rdfxml.xmlinput.impl.ParserSupport.warning(ParserSupport.java:147)
	at org.apache.jena.rdfxml.xmlinput.states.Frame.warning(Frame.java:57)
	at org.apache.jena.rdfxml.xmlinput.states.WantLiteralValueOrDescription.startElement(WantLiteralValueOrDescription.java:38)
	at org.apache.jena.rdfxml.xmlinput.impl.XMLHandler.startElement(XMLHandler.java:121)
	at java.xml/com.sun.org.apache.xerces.internal.parsers.AbstractSAXParser.startElement(AbstractSAXParser.java:510)
	at java.xml/com.sun.org.apache.xerces.internal.parsers.AbstractXMLDocumentParser.emptyElement(AbstractXMLDocumentParser.java:183)
	at java.xml/com.sun.org.apache.xerces.internal.impl.XMLNSDocumentScannerImpl.scanStartElement(XMLNSDocumentScannerImpl.java:351)
	at java.xml/com.sun.org.apache.xerces.internal.impl.XMLDocumentFragmentScannerImpl$FragmentContentDriver.next(XMLDocumentFragmentScannerImpl.java:2710)
	at java.xml/com.sun.org.apache.xerces.internal.impl.XMLDocumentScannerImpl.next(XMLDocumentScannerImpl.java:605)
	at java.xml/com.sun.org.apache.xerces.internal.impl.XMLNSDocumentScannerImpl.next(XMLNSDocumentScannerImpl.java:112)
	at java.xml/com.sun.org.apache.xerces.internal.impl.XMLDocumentFragmentScannerImpl.scanDocument(XMLDocumentFragmentScannerImpl.java:534)
	at java.xml/com.sun.org.apache.xerces.internal.parsers.XML11Configuration.parse(XML11Configuration.java:888)
	at java.xml/com.sun.org.apache.xerces.internal.parsers.XML11Configuration.parse(XML11Configuration.java:824)
	at java.xml/com.sun.org.apache.xerces.internal.parsers.XMLParser.parse(XMLParser.java:141)
	at java.xml/com.sun.org.apache.xerces.internal.parsers.AbstractSAXParser.parse(AbstractSAXParser.java:1216)
	at java.xml/com.sun.org.apache.xerces.internal.jaxp.SAXParserImpl$JAXPSAXParser.parse(SAXParserImpl.java:635)
	at org.apache.jena.rdfxml.xmlinput.impl.RDFXMLParser.parse(RDFXMLParser.java:100)
	at org.apache.jena.rdfxml.xmlinput.impl.RDFXMLParser.parse(RDFXMLParser.java:88)
	at org.apache.jena.rdfxml.xmlinput.ARP.load(ARP.java:101)
	at org.apache.jena.riot.lang.ReaderRIOTRDFXML.parse(ReaderRIOTRDFXML.java:173)
	at org.apache.jena.riot.lang.ReaderRIOTRDFXML.read(ReaderRIOTRDFXML.java:72)
	at org.apache.jena.riot.RDFParser.read(RDFParser.java:420)
	at org.apache.jena.riot.RDFParser.parseNotUri(RDFParser.java:406)
	at org.apache.jena.riot.RDFParser.parse(RDFParser.java:356)
	at org.apache.jena.riot.RDFParserBuilder.parse(RDFParserBuilder.java:570)
	at org.apache.jena.riot.RDFDataMgr.parseFromReader(RDFDataMgr.java:728)
	at org.apache.jena.riot.RDFDataMgr.read(RDFDataMgr.java:287)
	at org.apache.jena.riot.RDFDataMgr.read(RDFDataMgr.java:271)
	at org.apache.jena.riot.adapters.RDFReaderRIOT.read(RDFReaderRIOT.java:62)
	at org.apache.jena.rdf.model.impl.ModelCom.read(ModelCom.java:245)

[afs]

The error occurs because of two objects:

        <Outer xmlns="http://BASE/">
          <Prop>
            <A/>
            <B/>
          </Prop>
        </Outer>

Only the SAX based RRX parser is affected - the two StAX based ones, and ARP, detect this mistake.

Parsing OWLx (".owx") as RDF/XML and expecting an error isn't guaranteed. There are some simple documents that will pass.