If a type is provided using Value
syntax, additional conversions are performed. All types accept either an
atom or Prolog string holding a valid RDF lexical value for the type and
xsd:float and xsd:double accept a Prolog integer.
user. Subject and Predicate are resources. Object is either a resource or a term
literal(Value). See rdf/3 for an explanation of Value for typed and language qualified literals. All arguments are subject to name-space expansion. Complete duplicates (including the same graph and `line' and with a compatible `lifespan') are not added to the database.