code: public void addTriple(final String subject, final String predicate, final String value,
              final String datatype, final String language) {
          addQuad(subject, predicate, value, datatype, language, "@default");
      }
docs: Adds a triple to the @default graph of this dataset
  
  @param subject
  the subject for the triple
  @param predicate
  the predicate for the triple
  @param value
  the value of the literal object for the triple
  @param datatype
  the datatype of the literal object for the triple (null values
  will default to xsd:string)
  @param language
  the language of the literal object for the triple (or null)