Tim Stockheim

Optimization heuristics for the combinatorial auction problem

This work presents and compares three heuristics for the combinatorial auction problem. Besides a simple greedy (SG) mechanism, two metaheuristics, a simulated annealing (SA), and a genetic algorithm (GA) approach are developed which use the combinatorial auction process to find an allocation with maximal revenue for the auctioneer. The performance of these three heuristics is evaluated in the context of a price controlled resource allocation process designed for the control and provision of distributed information services. Comparing the SG and SA method shows that depending on the problem structure the performance of the SA is up to 20% higher than the performance of the simple greedy allocation method. The proposed GA approach, using a random key encoding, results in a further improvement of the solution quality. Although the metaheuristic approaches result in higher search performance, the computational effort in terms of used CPU time is higher in comparison to the simple greedy mechanism. However, the absolute overall computation time is low enough to enable real-time execution in the considered IS application domain.

Standardizing Interactive Pricing for Electronic Business

Interactive pricing, the subset of dynamic pricing where buyers and sellers enter a computer mediated price-negotiation process, has stimulated academic interest ever since the introduction of Internet-related B2C and B2B applications. However, this has not yet led to the widespread use of standardized interactive pricing mechanisms within industrial applications. A recent study suggests that applicants expect the integration of interactive pricing mechanisms into existing IT infrastructure to be very costly due to high customization efforts. The standardization of interactive pricing should thus be a first step towards enabling a wider use of these mechanisms. Building on the classification of the range of dynamic pricing methods, we analyze existing business standards that should be capable of describing interactive pricing mechanisms. Our analysis reveals the shortcomings of recent business standards which therefore require the development of an enhanced model for interactive pricing applications. Addressing this issue we propose a model that integrates a price communication language with a process description format for the customization of interactive pricing mechanisms. The paper concludes with three case studies illustrating the use of our model.

Dispositive Supply-Web-Koordination durch Multiagentensysteme

Globaler Wettbewerb sowie sich rasch ver-andernde und zunehmend individualisie-rende Kundenbedurfnisse forcieren eineKonzentration von Unternehmen auf ihreKernkompetenzen und eine Veranderungder Produktionsstruktur von Sachguternund Dienstleistungen [Shen et al. 99]. Esentstehen komplexe Wertschopfungsnetz-werke aus Entitaten, die Tatigkeiten wieBeschaffung von Rohstoffen, Transfor-mation dieser Rohstoffe in Halbfertig-und Fertigprodukte sowie die Verteilungder Fertigprodukte an die Konsumentendurchfuhren (vgl. Bild 1). In der Literaturwerden solche Wertschopfungsnetzwerkeals Supply Chains bezeichnet [GaHa95;Swam et al. 98; LeBi95]. Aufgrund ihrerheute meist netzwerkartigen Struktursprechen wir im Folgenden jedoch vonSupply Networks bzw. Supply Webs undmeinen damit das gesamte Wertschop-fungsnetzwerk eines bestimmten an dieEndkunden zu verausernden Produktes.Die Wohlfahrt jeder Entitat in einemsolchen Supply Web hangt von der Leis-tung der anderen Entitaten ab sowie vonderen Bereitschaft und Fahigkeit zu ko-operieren. Zum Beispiel wird die Fahigkeiteines Lieferanten, die Nachfrage von Kun-den zu befriedigen, von der Bereitschaftund Fahigkeit der Kunden bestimmt, dieNachfrage dem Zulieferer in einer korrek-ten und fristgerechten Art und Weise mit-zuteilen. Beim Fehlen einer solchen Kom-munikation kann der Zulieferer gezwun-gen sein, mit hoheren Lagerbestanden zuarbeiten, um Fehlmengenkosten zu redu-zieren. Die hoheren Lagerbestandskostenwerden letztendlich von den Kunden inForm von Preisaufschlagen fur die Pro-dukte getragen [Swam et al. 95].Das Supply-Chain-Management-Kon-zept basiert auf einer ganzheitlichen Be-trachtung des Supply Web und berucksich-tigt die Interdependenzen zwischen deneinzelnen Entitaten [Vahr99]. Im Zentrumsteht die integrierte Planung, Steuerungund Kontrolle des gesamten Netzwerksvom ersten Lieferanten bis zum Endkun-den [Schu et al. 96] [Mert95] [Schu97]. Vo-raussetzung hierfur ist eine Kooperationaller an dem Supply Web beteiligten Un-ternehmen [Vahr99].Entitaten bzw. Unternehmen in einemSupply Web sind jedoch autonome Orga-nisationseinheiten, die sich nur so langekooperativ verhalten, wie dies in ihrem ei-genen Interesse liegt [Kjen98, 41]. Auser-dem konnen die Entitaten in einem SupplyWeb mit Zulieferern und Kunden verbun-den sein, die wiederum ihre eigenen Zulie-ferer und Kunden besitzen. Daher bestehtdie Moglichkeit, dass sich Supply Websuberlappen bzw. Unternehmen parallel alsAkteure in verschiedenen Supply Webswirken (vgl. Bild 1). So kann ein Teilezulie-ferer wie z. B. ein Monitor-Produzent derZulieferer von zwei verschiedenen Com-puter-Herstellern sein. Daraus folgt wie-derum, dass etwa zwei Unternehmen, dieim Rahmen eines Supply Web miteinanderkooperieren, gleichzeitig bezuglich zweieranderer Wertschopfungsnetzwerke inKonkurrenz zueinander stehen konnen. Inder englischsprachigen Literatur hat sichfur diesen Sachverhalt der Begriff „Coo-petition“ herausgebildet, zusammenge-setzt aus Cooperation und Competition[BuKo99; BrNa96; Kjen98, 39]. Fur unse-ren Monitor-Hersteller ist es sehr schwie-rig, wenn nicht unmoglich, seine Produkti-onsplanung in Abstimmung mit der Pro-duktionsplanung bzw. gemas den Zielenbeider Kunden zur selben Zeit zu optimie-ren. Ein zentrales Supply Web Manage-ment, also eine zentrale Planung desgesamten Wertschopfungsnetzwerkes, er-scheint daher in solchen Fallen nicht odernur sehr schwierig durchsetzbar. Gefor-dert wird eine kontinuierliche und dezen-trale Planung im Rahmen eines verteiltenSupply Web Management [Kjen98, 3, 5,39].Supply Chain Management basiert aufder integrierten Informationsverarbeitungim gesamten Supply Web [BuKo99, 2, 62].Hierzu dienen Supply-Chain-Manage-ment-Systeme, welche den Informations-fluss innerhalb des Wertschopfungsnetz-werkes unterstutzen sowie eine Entschei-dungsunterstutzung und Automatisierungvon Planungs-, Steuerungs- und Kontroll-

Agents' bidding strategies in a combinatorial auction controlled grid environment

In this article we present an agent-based simulation environment for task scheduling in a grid-like computer system. The scheduler allows to one simultaneously allocate resources such as CPU time, communication bandwidth, volatile and non-volatile memory by employing a combinatorial resource allocation mechanism. The allocation is performed by an iterative combinatorial auction in which proxy-bidding agents try to acquire their desired resource allocation profiles with respect to limited monetary budget endowments. To achieve an efficient allocation process, the auctioneer provides resource price information to the bidders. We use a pricing mechanism based on shadow prices in a closed loop system in which the agents use monetary units awarded for the resources they provide to the system for the acquisition of complementary capacity. Our objective is to identify optimal bidding strategies in the multi-agent setting with respect to varying preferences in terms of resource quantity and waiting time for the resources. Based on a utility function we characterize two types of agents: a quantity maximizing agent with a low preference for fast bid acceptance and an impatient bidding agent with a high valuation of fast access to the resources. By evaluating different strategies with varying initial bid pricing and price increments, it turns out that for quantity maximizing agents patience and low initial bids pay off, whereas impatient agents should avoid high initial bid prices.

The impact of reputation on supply chains. An analysis of permanent and discounted reputation

In long-term recurring contractual relationships, which are common in the B2B-arena, reputation and trust play a crucial role. This analysis investigates the joint impact of reputation and price-based ranking of suppliers on the material flow in the supply chain. Positive reputation proves to be a key factor in reaching dominating market positions, which illustrates the importance of building brand awareness in all stages of a supply chain. Through our simulation, it will be observed that the ranking of suppliers by reputation-based choice has a stabilizing effect on the material flow in the supply chain. A strong reputation component in the individual choice stimulates the formation of monopolies, while the discount of reputation imposes a countertendency on this effect. The Bullwhip Effect, another phenomenon that carries a countertendency to the reputation-based monopoly effect, is observed to be even stronger for members of tiers with a high fluctuation of order rates.

A Diffusion Model for Communication Standards in Supply Networks

This article presents a simulation framework that analyzes the diffusion of communication standards in different supply networks. We show that agents’ decisions depend on potential cost reduction, pressure from members of their communication network, and implementation costs of their communication standards. Besides focusing on process-specific market power distributions, the impact of relationship stability and process connectivity is analyzed as determinants of the diffusion of communication standards within different supply network topologies. In this context, two real-world scenarios from the automotive and paper/publishing industries are used as examples for different network topologies. The results support the thesis that increasing relationship dynamics and process connectivity lead to decreasing competition of communication standards. In certain circumstances, local communication clusters appear along the value chain, enabling these clusters to preserve their globally inferior standardization decision.

Intelligente Tourenplanung mit DynaRoute

AbstractDue to increasing transportation costs and a rising demand for quality services professional optimization and planning of transport processes becomes a critical success factor for many companies. This article provides a detailed description of the software DynaRoute, capable to reduce transportation costs and at the same time increase customer satisfaction. The main results are: ▪Effective planning software enables companies to reduce transport costs by 10% and more while significantly improving service quality for the customer.▪A successful implementation of the software often requires organizational changes in the affected business processes.▪DynaRoute provides companies with the flexibility to take individual planning criteria into account.▪Advanced learning models allow for highly improved travel time predictions and this way increase the timeliness of deliveries.

Trust-Based Distributed Supply-Web Negotiations

This chapter presents a decentralized negotiation protocol for cooperative economic scheduling in a supply chain environment. These protocols are evaluated using software agents that maximize their profits by optimizing their local schedule and offer side payments to compensate other agents for lost profit or extra expense if cumulative profit is achievable. To further increase their income the agents have to apply a randomized local search heuristic to prevent the negotiation from stopping in locally optimal contracts. We show that the welfare could be increased by using a search strategy similar to Simulated Annealing. Unfortunately, a naive application of this strategy makes the agents vulnerable to exploitation by untruthful partners. We develop and test a straightforward mechanism based on trust accounts to protect the agents against systematic exploitation. This “Trusted” Simulated Annealing mechanism assures truthful revelation of the individual opportunity cost situation as the basis for the calculation of side payments.