anchor.diff:  unit BoxOfficeUnit;
   
   rule BoxOfficeIsOpen when
  -    $box: /boxOffices{ open }
  +    $box: /boxOffices[ open ]
   then
       drools.guard( TicketIssuerUnit.class );
   end
  
positive.code: unit Unit0
  
  rule GuardAgeCheck when
      $i: /input{ #Integer }
      $s: /input{ #String }
  then
      drools.guard( new AgeCheckUnit($i) );
      drools.guard( new AgeCheckUnit($s.length()) );
  
negative.code: unit AdultUnit
  
  rule Adult when
      $p : /persons[age >= adultAge]
  then
      System.out.println($p.getName() + " is adult and greater than " + adultAge);
  end
  