public static boolean simpleSubrelationPropositionP(Proposition proposition) {
    return ((proposition.operator == Logic.SGT_PL_KERNEL_KB_SUBSET_OF) &&
        (Stella_Object.isaP((proposition.arguments.theArray)[0], Logic.SGT_LOGIC_NAMED_DESCRIPTION) &&
         Stella_Object.isaP((proposition.arguments.theArray)[1], Logic.SGT_LOGIC_NAMED_DESCRIPTION)));
  }