Algernon Tutorial 4.c
System Design

System Design

1. Ontology Changes
   1. Make a subclass of Person called Customer.
   2. Add slot address from Customer to String. Use slot phone_number on Customer.
   3. Create a slot advertisements from Customer to Advertisement.
   4. Create a cost slot from Advertisement to Float. Calculate its value based on the number of words in the ad.
   5. Make a new subclass of Transaction called Payment.
   6. Create a slot payments from Customer to Payment.
   7. Create new transaction slots: amount, Date.
   8. Create a Balance slot from Customer to Number.
   9. Create a rate_per_word slot from Advertisement to Float.
2. Later, we realized we also needed:
   1. A content_size slot from Content to Integer.
   2. Instead of an advertisements slot on Customer, use the purchaserOf slot that is the inverse of purchaser. This was renamed from inverse_of_purchaser.
   3. Add a payer slot from Payment to Customer, with inverse slot payments.
   4. Create a Reports class that contains generated reports.
3. Rules
   1. FC: calculate cost of ad when the content of the ad changes. Get rate per word from the rate_per_word slot on Advertisement.
   2. FC: Validation: payment must be > 0.00.
   3. BC: Produce a report of all customers with a balance > 0.00.
   4. FC: Calculate cost of the ad, add it to customer's balance.
   5. FC: When a new payment is received, subtract from customer's balance.
4. Testing
   1. Create a new customer. ((:ADD-INSTANCE (?x Customer) (:NAME ?x TestCustomer)))
   2. Assert the content_size of the Personals Ad "Silly". Assert a purchaser for it too. ((content_size instance_00091 75) (purchaser instance_00091 TestCustomer))
   3. Or create a new ad and assert its rate_per_word and content_size. This should fire Rule 1, which should fire Rule 3.
   4. Then you can get the list of customers with balances, using ask: ((BalanceReport Reports ?report))
   5. Then, assert a payment for the purchaser of the ad, and check the balance again.

Notes

• We store rules as instances of :ALGERNON-RULE, which is a subclass of :CONSTRAINT. This is where Protégé likes rules to be kept.
• A rule stored in the KB requires three slots:
  • RuleBody: :ALGERNON-RULE to :STRING.
  • RuleClass: :ALGERNON-RULE to a subclass of :THING.
  • RuleSlot: :ALGERNON-RULE to an instance of :SLOT. This restricts the rule to firing only when the given slot is modified.
• You can also add a RuleTraceLevel slot from :ALGERNON-RULE to one of a list of symbols: {:SILENT, :NORMAL, :VERBOSE, :DETAIL, :DEBUG}. Make :NORMAL be the default.
• We also recommended that you add the :NAME and :DOCUMENTATION slots to rules.
• The rule to produce a report is the hardest to set up. It needs to be triggered by querying a slot of a frame. Let's set up a Reports class, with each report being an instance. We'll generate one report a day.