Marking scheme for A1

Correctness: 15 marks
   rules        ... / 8 marks (2 for each predicate)
      murderer
      no_alibi
      motive
      interest
   facts        ... / 6 marks
   solve        ... / 1 mark

Comments        ... / 2 marks

Testing         ... / 3 marks 
 (queries and answers for each predicate)


Total:  ... /  Out of 20 marks