public KifRelationalSentence(KifConstant constant, KifSequence <KifTerm> terms, KifSequenceVariable variable)
 {
     if (constant == null)
     {
         throw new ArgumentNullException("Constant cann't be null");
     }
     _constant = constant;
     _variable = variable;
     _terms    = new KifSequence <KifTerm>(terms);
 }
 public KifRelationalSentence(KifConstant constant, KifTerm term)
     : this(constant, new KifSequence <KifTerm>(term), null)
 {
 }
 public KifRelationalSentence(KifConstant constant, KifSequence <KifTerm> terms) : this(constant, terms, null)
 {
 }