RDFParser always parse subjects and objects as strings
In the classes NaturalFullRDFTranslator, NaturalRDFTranslator and RawRDFTranslator, everything is parsed into strings by using the method stringValue instead of creating a specific literal type when it is relevant.
This an inconsistent behavior with the DlgpParser where literals in dlgp that are integers, floating numbers or booleans are parsed as a specific type. This causes errors in the reasoning process when both RDF data and Dlgp are used together. For example, if we have the rule r(X) :- p(X, 1). in dlgp and we have p(1, 1) in RDF format, the rule will not be applicable since we will have 1 as an Integer in the dlgp rule and as the String "1" in the RDF data.