## eMediator: A Next Generation Electronic Commerce Server (2002)

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Venue: | Computational Intelligence |

Citations: | 116 - 31 self |

### BibTeX

@INPROCEEDINGS{Sandholm02emediator:a,

author = {Tuomas Sandholm},

title = {eMediator: A Next Generation Electronic Commerce Server},

booktitle = {Computational Intelligence},

year = {2002},

pages = {73--96}

}

### Years of Citing Articles

### OpenURL

### Abstract

This paper presents eMediator, an electronic commerce server prototype that demonstrates ways in which algorithmic support and game-theoretic incentive engineering can jointly improve the efficiency of ecommerce. eAuctionHouse, the configurable auction server, includes a variety of generalized combinatorial auctions and exchanges, pricing schemes, bidding languages, mobile agents, and user support for choosing an auction type. We introduce two new logical bidding languages for combinatorial markets: the XOR bidding language and the OR-of-XORs bidding language. Unlike the traditional OR bidding language, these are fully expressive. They therefore enable the use of the Clarke-Groves pricing mechanism for motivating the bidders to bid truthfully. eAuctionHouse also supports supply/demand curve bidding. eCommitter, the leveled commitment contract optimizer, determines the optimal contract price and decommitting penalties for a variety of leveled commitment contracting mechanisms, taking into account that rational agents will decommit strategically in Nash equilibrium. It also determines the optimal decommitting strategies for any given leveled commitment contract. eExchangeHouse, the safe exchange planner, enables unenforced anonymous exchanges by dividing the exchange into chunks and sequencing those chunks to be delivered safely in alternation between the buyer and the seller.

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Citation Context ...dder has preferences over bundles, that is, combinations of items (as is often the case for example in electricity markets, equities trading, bandwidth auctions [16, 17], and transportation exchanges =-=[27]-=-), then bidding in such auctions is difficult. To determine her valuation for an item, the bidder needs to guess what items she will receive in later auctions. This requires speculation on what the ot... |

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Citation Context ...nnot (and should not) restrict the number of bids submitted. The algorithm scales up well in practice. For details and experimental results, see [30]. The algorithm has been further refined by others =-=[5]-=-, and we then designed a completely different search algorithm that promised to be drastically faster [35]. Recently, we developed yet a faster algorithm, CABOB, for the problem. Experimental results ... |

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Citation Context ...ms are auctioned one at a time. If a bidder has preferences over bundles, that is, combinations of items (as is often the case for example in electricity markets, equities trading, bandwidth auctions =-=[16, 17]-=-, and transportation exchanges [27]), then bidding in such auctions is difficult. To determine her valuation for an item, the bidder needs to guess what items she will receive in later auctions. This ... |

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Citation Context ... the OR-of-XORs language, it is fully expressive and never less compact. Furthermore, it was shown that there exist preferences for which it is exponentially more compact than the OR-of-XORs language =-=[19]-=-. We believe, however, that the OR-of-XORs language is more natural. 5 Optimark Technologies, Inc. does a fuzzier match where each bidder specifies how much she prefers different regions of the price-... |

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Citation Context ...ototype called eAuctionHouse. Several successful commercial Internet auction sites already exist— such as eBay and Yahoo—and interesting academic auction houses have recently appeared on the Inter=-=net [25, 45]-=-. Our motivation in developing an auction server was to prototype novel next generation features, and test their feasibility both computationally and in terms of user comfort. eAuctionHouse allows use... |

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Citation Context ...ms are auctioned one at a time. If a bidder has preferences over bundles, that is, combinations of items (as is often the case for example in electricity markets, equities trading, bandwidth auctions =-=[16, 17]-=-, and transportation exchanges [27]), then bidding in such auctions is difficult. To determine her valuation for an item, the bidder needs to guess what items she will receive in later auctions. This ... |

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Citation Context ...or a plane, the bidder is willing to take any one of a host of slots, but does not want more than one. To address this, we introduced the XOR bidding language, which has become popular recently (e.g. =-=[20]-=-). In this language, each bidder can submit one XOR disjunct, that is, each bidder can submit multiple bids (each bid including a set of items and a price), but only one bid from any given bidder can ... |

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Citation Context ...ms prevail as in sequential auctions, albeit in a mitigated form. Combinatorial auctions can be used to overcome the need for lookahead and the inefficiencies that stem from the related uncertainties =-=[17, 24, 26, 27]. -=-In a combinatorial auction bidders may place bids on combinations of items. This allows the bidders to express complementarities between items instead of having to speculate into an item’s valuation... |

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Citation Context ...re bi(S) is the bid of agent i on combination S. But what would happen if 1We proved this via an approximation-preserving polynomial reduction from maximum clique (which is known to be inapproximable =-=[9]).-=- 3sagent 1 bid b1({1}) = $5, b1({2}) = $4, and b1({1,2}) = $7, and there were no other bidders? The auctioneer could allocate items 1 and 2 to agent 1 separately, and that agent’s bid for the combin... |

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Citation Context ...he table). Recent research has focused on developing even faster winner determination algorithms for multi-unit combinatorial auctions [13, 35], and for single- and multi-unit combinatorial exchanges =-=[35, 39]-=-. 2.2 Bidding via price-quantity graphs For markets where there is one item for sale, but multiple indistinguishable units of it, eAuctionHouse supports price-quantity graphs (that is, supply curves a... |

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Citation Context ...that just did not win (aka. the uniform-price auction). Our auction server uses the former method because the latter is not incentive compatible: it falls prey to demand reduction lies by the bidders =-=[1]. -=-For multi-item auctions (with one or more units per item), the Groves-Clarke mechanism, as discussed earlier, is the appropriate generalization of the Vickrey auction. Each bidder’s dominant strateg... |

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Citation Context ...e to extract truthful valuation revelations as the bids to the auctioneer. Bidding truthfully can be made incentive compatible (a dominant strategy) by using the Groves-Clarke mechanism (Groves 1973; =-=Clarke 1971-=-). This means that each bidder is motivated to bid truthfully irrespective of what the others bid. This renders counterspeculation unnecessary. The Groves-Clarke mechanism can be applied to the combin... |

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Citation Context ... CABOB, for the problem. Experimental results show that it is currently the fastest algorithm for optimal winner determination, scaling to hundreds of items and thousands or tens of thousands of bids =-=[38]. 2.1.2 -=-The XOR bidding language The OR bidding language implicitly assumes that the bids are superadditive: bi(S ∪ S ′ ) ≥ bi(S)+bi(S ′ ) where bi(S) is the bid of agent i on combination S. But what ... |

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Citation Context ...mine how much each agent should underbid as a function of her valuation. The second-price (Vickrey) auction charges the winning bidder the price of the second highest bid. Under certain restrictions (=-=Sandholm 1996-=-a), it is each bidder 's dominant strategy to bid her true valuation (Vickrey 1961). The multi-unit Vickrey auction is a generalization of the Vickrey auction to settings with multiple units of an ite... |

109 | Negotiation Among Self-Interested Computationally Limited Agents
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Citation Context ...oes not hinder distributive bargaining (dividing the expected benefit). However, this independence only holds if the decommitment penalties are tailored to the chosen contract price. 13sothers do not =-=[28, 32]-=-. Similarly, some sequences of delivering given chunks are safe while others are not. As part of eMediator, we built a safe exchange planner called eExchangeHouse. As input, the planner takes the foll... |

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Citation Context ...ototype called eAuctionHouse. Several successful commercial Internet auction sites already exist— such as eBay and Yahoo—and interesting academic auction houses have recently appeared on the Inter=-=net [25, 45]-=-. Our motivation in developing an auction server was to prototype novel next generation features, and test their feasibility both computationally and in terms of user comfort. eAuctionHouse allows use... |

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Citation Context ...g because there is a chance that the other party will decommit, in which case the former agent gets freed from the contract, does not have to pay a penalty, and collects a penalty from the breacher. (=-=Sandholm & Lesser 1996-=-) showed that despite such insincere decommitting, leveled commitment increases each contract party's expected payoff, and enables contracts in settings where no full commitment contract is beneficial... |

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Citation Context ... because agents do not have exact information about each others’ preferences. This often leads to inefficient allocations where bidders fail to get the combinations they want and get ones they do no=-=t [2, 29]. -=-In a parallel auction the items are open for auction simultaneously and bidders may place their bids during a certain time period. This has the advantage that the others’ bids partially signal to th... |

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Citation Context ...out the priors from which the bidders’ private valuations are drawn, a Nash equilibrium analysis can be conducted to determine how much each agent should underbid as a function of her valuation (e.g=-=. [44]).-=- The second-price (Vickrey) auction charges the winning bidder the price of the second highest bid. Under certain restrictions [29], it is each bidder’s dominant strategy to bid her true valuation [... |

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Citation Context ...thm can guarantee an allocation within a bound n 1−ɛ from optimum for any ɛ>0 (unless NP = ZPP) [30]. 1 If the bids exhibit special structure, better approximations can be achieved in polynomial t=-=ime [3, 7, 8, 10, 35]-=-, but even these guarantees are so far from optimum that they are irrelevant for auctions in practice [30]. Polynomial time winner determination can be achieved by restricting the combinations on whic... |

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Citation Context ... To this end, we introduced the 2 A recent paper shows that if each bidder is interested in only one bundle, then incentive compatibility can be guaranteed even under approximate winner determination =-=[12]-=-. 3 One idea toward this direction was presented early on by Rassenti et al [24]. They allowed each bidder to place combinatorial bids and to state the maximal number of bids that could be accepted fr... |

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Citation Context ...rantees: Proposition 2.2 No polytime algorithm can guarantee an allocation within a bound 1 n 1\Gammaffl from optimum for any ffl ? 0 (unless NP equals probabilistic polytime). The proof is based on (=-=Hastad 1999-=-), and we present it in (Sandholm 1999). If the bids exhibit special structure, better approximations can be achieved in polynomial time (Chandra & Halld'orsson 1999; Halld'orsson 1998; Hochbaum 1983;... |

64 | Some tractable combinatorial auctions
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Citation Context ...so far from optimum that they are irrelevant for auctions in practice [30]. Polynomial time winner determination can be achieved by restricting the combinations on which the agents are allowed to bid =-=[21, 26, 35, 42]-=-. However, because the agents may then not be able to bid on the combinations they want, similar economic inefficiencies prevail as in noncombinatorial auctions. We recently generated another approach... |

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Citation Context ...have incentive to underbid strategically. Bidding truthfully can be made incentive compatible (a weakly dominant strategy) by using the GrovesClarke mechanism [4, 6] (aka. generalized Vickrey auction =-=[15]-=-). This means that each bidder is motivated to bid truthfully irrespective of how the others bid. This renders counterspeculation unnecessary. With unrestricted bidder preferences, the Groves-Clarke m... |

61 | M.: An algorithm for multi-unit combinatorial auctions
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Citation Context ...ding language (the number of units is specified in each cell of the table). Recent research has focused on developing even faster winner determination algorithms for multi-unit combinatorial auctions =-=[13, 35]-=-, and for single- and multi-unit combinatorial exchanges [35, 39]. 2.2 Bidding via price-quantity graphs For markets where there is one item for sale, but multiple indistinguishable units of it, eAuct... |

61 | Issues in computational Vickrey auctions
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Citation Context ... because agents do not have exact information about each others’ preferences. This often leads to inefficient allocations where bidders fail to get the combinations they want and get ones they do no=-=t [2, 29]. -=-In a parallel auction the items are open for auction simultaneously and bidders may place their bids during a certain time period. This has the advantage that the others’ bids partially signal to th... |

46 | Equilibrium analysis of the possibilities of unenforced exchange in multiagent systems
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Citation Context ...unning such an intermediary, which is recovered as fees—currently about 3-5% of the contract price—from the contract parties. A method for tackling this problem without third parties was developed=-= in [32]-=-. The exchange is divided into chunks where each party delivers a small amount at a time, and the exchange proceeds with such alternation. The method targets settings where dividing the goods into chu... |

44 | Leveled Commitment Contracts and Strategic Breach
- Sandholm, Lesser
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(Show Context)
Citation Context ... large and unknown. Also, when events are not mutually observable, the observing agent can lie about what transpired. Leveled commitment contracts are another method for capitalizing on future events =-=[33]-=-. Instead of conditioning the contract on future events, a mechanism is built into the contract that allows unilateral decommitting. This is achieved by specifying in the contract the level of commitm... |

42 | Market clearability
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(Show Context)
Citation Context ...ach party is cleared at a potentially different price) is NP-complete. If the curves are linear, then even discriminatory clearing can be done in polynomial time. These results hold both for auctions =-=[36]-=- and for exchanges [37]. 2.3 Support for choosing an auction type The auction server, eAuctionHouse, supports a wide variety of auction types. The user that sets up a given auction (she may be a buyer... |

40 | Algorithms for optimizing leveled commitment contracts
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(Show Context)
Citation Context ... are linear within each rectangle. In that case, the equation group can be easily solved in constant time. Our optimizer solves the problem in this way for each rectangle separately. For details, see =-=[34]-=-. 12s3.2 Using eCommitter to find optimal contracts In addition to determining how agents should play under a given leveled commitment contract, eCommitter also determines the optimal leveled commitme... |

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Citation Context ...thm can guarantee an allocation within a bound n 1−ɛ from optimum for any ɛ>0 (unless NP = ZPP) [30]. 1 If the bids exhibit special structure, better approximations can be achieved in polynomial t=-=ime [3, 7, 8, 10, 35]-=-, but even these guarantees are so far from optimum that they are irrelevant for auctions in practice [30]. Polynomial time winner determination can be achieved by restricting the combinations on whic... |

25 |
Unenforced e-commerce transactions
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(Show Context)
Citation Context ..., which is recovered as fees - currently about 5% of the contract price - from the contract parties. A method for tackling this problem without third parties was developed by (Sandholm & Lesser 1995; =-=Sandholm 1997-=-). The exchange is divided into chunks where each party delivers a small amount at a time, and the exchange proceeds with such alternation. The method is most suitable for settings where dividing the ... |

19 | Optimal clearing of supply/demand curves
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(Show Context)
Citation Context ... a potentially different price) is NP-complete. If the curves are linear, then even discriminatory clearing can be done in polynomial time. These results hold both for auctions [36] and for exchanges =-=[37]-=-. 2.3 Support for choosing an auction type The auction server, eAuctionHouse, supports a wide variety of auction types. The user that sets up a given auction (she may be a buyer, a seller, or a third ... |

17 | Approximations of independent sets in graphs
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(Show Context)
Citation Context ...thm can guarantee an allocation within a bound n 1−ɛ from optimum for any ɛ>0 (unless NP = ZPP) [30]. 1 If the bids exhibit special structure, better approximations can be achieved in polynomial t=-=ime [3, 7, 8, 10, 35]-=-, but even these guarantees are so far from optimum that they are irrelevant for auctions in practice [30]. Polynomial time winner determination can be achieved by restricting the combinations on whic... |

16 |
A strategy for decreasing the total transportation costs among area-distributed transportation centers. Nordic operations analysis in cooperation (noas): Or in business, turku school of economics
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Citation Context ...used to overcome the need for lookahead and the inefficiencies that stem from the related uncertainties (Rassenti, Smith, & Bulfin 1982; Sandholm 1993; Rothkopf, Pekec, & Harstad 1998; McMillan 1994; =-=Sandholm 1991-=-). In a combinatorial auction bidders may place bids on combinations of items. This allows the bidders to express complementarities between items instead of having to speculate into an item's valuatio... |

14 | Constrained multi-object auctions and b-matching
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Citation Context ...so far from optimum that they are irrelevant for auctions in practice [30]. Polynomial time winner determination can be achieved by restricting the combinations on which the agents are allowed to bid =-=[21, 26, 35, 42]-=-. However, because the agents may then not be able to bid on the combinations they want, similar economic inefficiencies prevail as in noncombinatorial auctions. We recently generated another approach... |

11 | Surplus equivalence of leveled commitment contracts
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(Show Context)
Citation Context ...bset of these games. In such games all of the probability mass of f(ă) and/or g( ˘ b) is on one point. 8 A recent paper shows that this restriction does not reduce the welfare of the contract partie=-=s [41]. 11sIf the co-=-ntractee has decommitted, the contractor’s best move is not to decommit because −ă − a + b ≤−ă+b(because a ≥ 0). This also holds for a contract where neither agent has to pay a decommitm... |

9 | Safe exchange planner, in
- Sandholm, Ferrandon
(Show Context)
Citation Context ...where each step may include both a payment and a delivery. The chunking algorithms and the chunk sequencing algorithms are highly nontrivial; they are described and analyzed in detail in other papers =-=[28, 31, 32]. -=-Generally, a user (buyer or seller) only knows the desired inputs regarding himself. He can use bounds on the other party’s values and the exchange plan will still be safe. An upper bound can be use... |

8 |
Crossing Network Utilizing Optimal Mutual Satisfaction Density Profile
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(Show Context)
Citation Context ...owever, that the OR-of-XORs language is more natural. 5 Optimark Technologies, Inc. does a fuzzier match where each bidder specifies how much she prefers different regions of the price-quantity plane =-=[14]-=-. 5sFigure 1: An XOR disjunct in a multi-item, multi-unit combinatorial exchange. The example is from an electricity market scenario where the agents can bid for combinations of electricity for differ... |

8 | Im)possibility of safe exchange mechanism design
- Sandholm, Wang
- 2002
(Show Context)
Citation Context ...exchange mechanisms). In that general framework we uncover the conditions under which safe exchange is inherently possible or impossible—not just using our chunking mechanism, but using any mechanis=-=m [40]-=-. 16s5 Conclusions The eMediator electronic commerce server prototype exemplifies several new features that can facilitate more efficient ecommerce in the future. Each one of the three components exhi... |

5 |
Greedy local search and weighted set packing approximation
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Citation Context |

3 |
New NCL survey shows consumers are both excited and confused about shopping online
- League
- 1999
(Show Context)
Citation Context ... that once one party has received the item, he may be motivated to vanish without delivering his part of the contract. In fact, 6% of US people with online buying experience have reported nondelivery =-=[18]. -=-Nondelivery could be avoided by a trusted third party that takes the payment and goods, and carries out the transaction only after all parties have delivered their part to the intermediary. Today’s ... |