predicateObjectList in Turtle documents are not parsed correctly

[tobiaswjohn]

The following (valid) turtle document is not parsed correctly:

<iri1> <iri2> <iri3> ;
    ; 
    .

The problem is triggered by the second line with a semicolon without any verb and objectList, which is allowed based on the turtle grammar.

I assume the cause of the problem is the grammar in TurtleParser.jj line 264 were the rule for predicateObjectList looks different than the one from the standard.

The detailed error message when parsing the example on the top is the following:

Parser: org.semanticweb.owlapi.rdf.turtle.parser.TurtleOntologyParser@2cf3d63b
    Stack trace:
org.semanticweb.owlapi.rdf.turtle.parser.ParseException: Encountered unexpected token: ";" ";"
    at line 2, column 2.

Was expecting:

    "."
        org.semanticweb.owlapi.rdf.turtle.parser.TurtleOntologyParser.parse(TurtleOntologyParser.java:58)
        uk.ac.manchester.cs.owl.owlapi.OWLOntologyFactoryImpl.loadOWLOntology(OWLOntologyFactoryImpl.java:195)
        uk.ac.manchester.cs.owl.owlapi.OWLOntologyManagerImpl.load(OWLOntologyManagerImpl.java:1105)
        uk.ac.manchester.cs.owl.owlapi.OWLOntologyManagerImpl.loadOntology(OWLOntologyManagerImpl.java:1055)
        uk.ac.manchester.cs.owl.owlapi.OWLOntologyManagerImpl.loadOntologyFromOntologyDocument(OWLOntologyManagerImpl.java:1005)
        org.example.Main.loadTurtle(Main.java:87)
        org.example.Main.main(Main.java:23)
Encountered unexpected token: ";" ";"
    at line 2, column 2.

Was expecting:

    "."
        org.semanticweb.owlapi.rdf.turtle.parser.TurtleParser.generateParseException(TurtleParser.java:1034)
        org.semanticweb.owlapi.rdf.turtle.parser.TurtleParser.jj_consume_token(TurtleParser.java:902)
        org.semanticweb.owlapi.rdf.turtle.parser.TurtleParser.parseDocument(TurtleParser.java:160)
        org.semanticweb.owlapi.rdf.turtle.parser.TurtleOntologyParser.parse(TurtleOntologyParser.java:54)
        uk.ac.manchester.cs.owl.owlapi.OWLOntologyFactoryImpl.loadOWLOntology(OWLOntologyFactoryImpl.java:195)
        uk.ac.manchester.cs.owl.owlapi.OWLOntologyManagerImpl.load(OWLOntologyManagerImpl.java:1105)
        uk.ac.manchester.cs.owl.owlapi.OWLOntologyManagerImpl.loadOntology(OWLOntologyManagerImpl.java:1055)
        uk.ac.manchester.cs.owl.owlapi.OWLOntologyManagerImpl.loadOntologyFromOntologyDocument(OWLOntologyManagerImpl.java:1005)
        org.example.Main.loadTurtle(Main.java:87)
        org.example.Main.main(Main.java:23)



	at uk.ac.manchester.cs.owl.owlapi.OWLOntologyFactoryImpl.loadOWLOntology(OWLOntologyFactoryImpl.java:236)
	at uk.ac.manchester.cs.owl.owlapi.OWLOntologyManagerImpl.load(OWLOntologyManagerImpl.java:1105)
	at uk.ac.manchester.cs.owl.owlapi.OWLOntologyManagerImpl.loadOntology(OWLOntologyManagerImpl.java:1055)
	at uk.ac.manchester.cs.owl.owlapi.OWLOntologyManagerImpl.loadOntologyFromOntologyDocument(OWLOntologyManagerImpl.java:1005)
	at org.example.Main.loadTurtle(Main.java:87)
	at org.example.Main.main(Main.java:23)

[ignazio1977]

Indeed, the standard allows for separators that don't separate anything. One could argue whether it was intentional or a typo. I wonder what's the history behind that.