FIGURE 2: KnowledgePro (Windows) example of Inheritance

topic Item.
  (* Inventory class for stationery store. *)
  :price is getPrice().
  :supplier is getSupplier().
  :onHand is getOnHand().
 
  topic getPrice.
    (* Apply default 40% markup. *)
    ask ('What is our cost?', cost).
    getPrice is ?cost + (.40 * ?cost).
  end.
 
  topic getSupplier.
    getSupplier is 'East End Wholesale'.
  end.
 
  topic getOnHand.
    ask ('How many are on hand?', getOnHand).
  end.
 
end.
 
topic PenItem.
  (* PenItem is a subclass of Item. *)
  im_a (Item).
  topic getPrice.
    (* PenItem's unique getPrice method. *)
    ask('What is our cost?', cost).
    getPrice is ?cost + (.50 * ?cost).
  end.
end. (* PenItem *)
 
topic PaperItem.
  (* PaperItem is a subclass of Item. *)
  im_a (Item).
  topic getSupplier
    getSupplier is 'Paper World'.
  end.
end. (* PaperItem *)
 
topic GiftItem
  (* GiftItem is a subclass of Item. *)
  im_a (Item).
end. (* GiftItem *)