class RIF_Document
   
   subclass RIF_Core_Document
     property ruleset: set of RuleSetEntry
     property comment: string

class RuleSetEntry
  
   subclass Rule
      property if: Sentence
      property constraint: list of Equation

      subclass HornRule
         property then: AtomicSentence

      #   ADD THIS TO EXTEND CORE TO FOL
      subclass Implication
         property then: Sentence

class Sentence

   subclass Conjunction
      property conjuncts: list of Sentence

   subclass AtomicSentence
      property predicate: Term
      property sentenceArguments: list of Term

class Identifier

class Atom
             
          class Equation
             property left: Term
             property right: Term
          
          class AtomicSentence