Reports a warning from the parser. Warning messages are generated by the
parser when it encounters data that is syntactically correct but which is
likely to be a typo. Examples are the use of unknown or deprecated RDF
URIs, e.g. rdfs:Property instead of rdf:Property.
Reports an error from the parser. Error messages are generated by the
parser when it encounters an error in the RDF document. The parser will
try its best to recover from the error and continue parsing when
stopAtFirstError has been set to false.
Reports a fatal error from the parser. A fatal error is an error of which
the RDF parser cannot recover. The parser will stop parsing directly
after it reported the fatal error. Example fatal errors are unbalanced
start- and end-tags in an XML-encoded RDF document.