anchor.diff:  unit TicketIssuerUnit;
   
   rule IssueAdultTicket when
  -    $p: /persons{ age >= 18 }
  +    $p: /persons[ age >= 18 ]
   then
       tickets.insert(new AdultTicket($p));
   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 BoxOfficeUnit;
  
  rule BoxOfficeIsOpen when
      $box: /boxOffices[ open ]
  then
      drools.guard( TicketIssuerUnit.class );
  end
  