This section describes the most important and at the same time the most lively activity in the market: the bidding rounds. Such activity takes

Fig. 8 - The auctioneer

Fig. 9 - Buyers bidding
place in the auction room, in which buyers bid for boxes of fish that are presented by an auctioneer who calls prices in descending order - the downward bidding protocol.

We can identify several situations that may arise during each bidding round in the fish market:

  • Proper sale. When a buyer submits a bid that his credit can back up, it is turned into a sale.
  • Unsupported bid. When a buyer submits a bid that his credit cannot back up, the buyers' manager fines this bidder and the round is restarted by the auctioneer who calculates the new starting price by increasing 25% the price within the bid.
  • Collision. When two or more buyers submit the same bid, the auctioneer declares a collision and restarts the round. The new starting price is calculated by increasing 25% the collision price.
FM 96.5 implements faithfully all theses cases. Furthermore, two new cases are implemented:
  • Minimum price. Each good is assigned a minimum price when passing through the sellers' admitter office. When minimum prices are reached, the round is restarted.
  • Expulsion. When a buyer cannot even back up a fine, he is sent off the market and the round is restarted as usual: the auctioneer calculates the new starting price by increasing 25% the price within the bid.

It is worth noticing that FM 96.5 will start or restart a round whenever the boss authorizes the auctioneer. For instance, the boss might consider that three buyers in the auction room are not enough to start a round or that they are notenough goods to be auctioned yet.

The implementation of the downward bidding protocol has deserved special attention through the history of our developments. Our main concerns have been to preserve fairness and liveliness.

In FM 96.5 we regard the termination of each bidding round as the synchronization point. If a buyer is going to submit a bid, he will signal this as soon as the price reaches his target. The signal sent back to the auctioneer includes the price at which the buyer signalled his intention. It does not matter if the bid arrives after the price has gone down further. Then, as soon as the auctioneer receives a bid, he broadcasts to the buyers the information that a bid has been received, which they must acknowledge. If messages are transimitted on a reliable network, we must receive any late bids before we receive the acknowledgements, hence we have the standard two cases:

  • Proper sale.One bidder
  • Collision.Multiple bidders at the same price
and a new case:
  • Multiple bidders at different prices. In this case the highest price bid wins, or we restart, as usual.
Thus, premature bids, delayed bids, and spoofing are adequatelly avoided directly by the protocol implementation.

Figure 10 shows the information a buyer's remote control provides while a bidding round is on. Let us say that the auctioneer starts a new bidding round. First of all, he sends to each buyer the list of buyers taking part in the round, the list of goods in the auction room, and the next good to be auctioned. After that, the auctioneer starts broadcasting prices to all buyers in the auction room.


Fig. 10 - A buyer taking part in a bidding round

Let us suppose that this buyer submits a bid. Suppose also that this is the only bid submitted to the auctioneer or that this is the highest bid. In this case, the auctioneer will declare a winner of the current bidding round


Fig. 11 - Auctioneer declaring the winner of the round

so that the fish box being auctioned will be sold to the only bidder. The new purchase is added to the winner's list of purchases and his credit is updated accordingly.


Fig. 12 - Winner of round number 1

The auctioneer also reports the new sale to the sellers' manager and, in the end, the owner of the fish box is informed of the new sale by the sellers' manager. The seller's remote control updates the seller's earnings and adds the new sale to the list of sales.


Fig. 13 - Seller receiving a new sale

Note that during round number 1 the minimum price was reached but as we explained at the beginning of this section, the round was restarted by the auctioneer.

Let us now suppose that the auctioneer starts a new round during which the winner of the last round submits some bids that he cannot back up. Consequently, the auctioneer declares these bids as invalid and the buyers' manager fines the bidder.


Fig. 14 - Auctioneer fining and expelling a buyer

As we can see in the picture above, not only the bidder is fined but he is finally expelled. This is because he could not even back up one of the fines with which the buyers' manager fined him for submitting an invalid bid. Note also that the auctioneer finally declared the end of the round since the boss detects that there are not enough buyers when requested about the restart of the round.

The picture below shows that the buyer that has been expelled is informed of the reasons why his bids were turned out. Notice that the auctioneer informs these situations to the rest of buyers taking part in the round.


Fig. 15 - Buyer sent off of the market

There is only one case left: collision. Let us suppose then that two buyers submit the same bid. The pictures below show that both buyers involved in the collision are reported about it. After that, the auctioneer restarts the round.


Fig. 16 - Buyer involved in the collision


Fig. 17 - The other buyer involved in the collision

Important note: Before finishing this section, we would like to remark that all the examples above have been explained in terms of a graphical interface in order to make our examples more visual and understanding. Nonetheless, it is important not to forget that remote controls are capable of holding a dialogue with any foreign agent (whose code is unknown to our remote controls) whenever these agents limit their illocutions(messages) to the fixed protocol that remote controls understand.


http://www.iiia.csic.es/Projects/fishmarket/FM96-5/biddinground.html
fishmarket@iiia.csic.es
Updated: December, 6th 1996

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