Participants: The Buyer, The Seller

Other entities: The goods, the Money

Scenario:

    Initial state:

        The Buyer has the Money and wants the Goods.

        The Seller has the Goods and wants the Money.

    Exchange:

        The Buyer gives the Money to the Seller.

        The Seller gives the Goods to the Buyer.

    Final State:

        The Seller has the Money.

        The Buyer has the Goods.

Buy designates the giving of the Money to the Seller by the Buyer, and profiles the Buyer and the Goods and optionally profiles the Money and the Seller.

Sell designates the giving of the Goods to the Buyer by the Seller, profiles the Seller and the Goods and optionally profiles the Money and the Buyer.

Price designates the amount of the Money, and profiles the Money and the Goods.

Cost designates the Money from the perspective of the Buyer, and profiles the Goods and optionally the Buyer.