code: public static RAExpression alias(RAExpression re, RelationID alias, TermFactory termFactory) {
          return new RAExpression(re.dataAtoms, re.filterAtoms,
                  RAExpressionAttributes.alias(re.attributes, alias), termFactory);
      }
docs: (relational expression) AS A
  
  @param re a {@link RAExpression}
  @param alias a {@link QuotedID}
  @return a {@link RAExpression}