Thomas Tesch

Agents, a broker, and lies

Virtual enterprises need reliable and efficient cooperation mechanisms to carry out transactions between autonomous agents with conflicting interests. Available cooperation mechanisms either use bilateral multi-step negotiation or auctioning. Negotiations encourage agents to reason about the interests of their opponents. Thus, negotiations suffer from counter speculations. Auctions apply to asymmetric trading only; they either favor the auctioneer or the bidders. Both mechanisms do not promote agents to tell the truth. Therefore, we propose to use a trustbroker to mediate between the agents. We introduce three symmetric, negotiation free one-step protocols to carry out a sequence of decisions for agents with possibly conflicting interests. The protocols achieve substantially better overall benefit than random or hostile selection, and they avoid lies. We analyze the protocols with respect to informed vs. uninformed lies, and with respect to beneficial vs. malevolent lies, and show that agents are best off to know and announce their true interests. Analytical proofs and simulations substantiate our results.

Arbitration and Matchmaking for Agents with Conflicting Interests

The exchange of goods and services among software agents requires reliable and fair brokering mechanisms to match trading parties and to mediate among their conflicting interests. Available trading models for electronic marketplaces are fixed price selling, bilateral multi-step negotiations, and various forms of auctioning. These models demand trading parties to evaluate appropriate interest matches on their own and encourage them to pretend inexact interests to their advantage. We introduce an arbiter as intermediary that finds buyers and suppliers with best matching interests. The intermediary uses matching and arbitration protocols that ensure better overall benefit than random matches, avoid advantages for agents that manipulate their interests (lies), preserve the mutual privacy of interests of the trading parties, and, if desired, their anonymity. We analyse the protocols with respect to their applicability under various conditions, investigate their robustness with different utility distributions by simulations, and describe which forms of interest manipulations can be avoided.

Scheduling non-enforceable contracts among autonomous agents

With the emergence of fast and standardized communication infrastructures over which separately designed agents of different organizations can interact in real-time, there is an increasing demand for cooperation mechanisms that allow to carry out inter-organizational cooperations in a safe way. The lack of external control over an agents decisions, resources and actions hamper the usage of traditional transaction and workflow technology to make self-interested agents cooperate, i.e., agents cannot not be forced from a mediating cooperation instance to continue a cooperation. The challenge is, therefore, to design a cooperation mechanism that motivates cooperating agents to carry out a specified contract and, in case of unilateral defection, ensures that none of the cooperators can benefit from the situation. In this paper we present a domain independent framework how non-enforceable cooperations can be made safe against unilateral defection. We have developed a utility-based scheduling algorithm that keeps a cooperation in equilibrium and that motivates agents to continue a cooperation as long as it is for all participants beneficial.

ARBITRATION PROTOCOLS FOR COMPETING SOFTWARE AGENTS

The exchange of goods and services between bargaining software agents requires new forms of brokering mechanisms which achieve consensus between conflicting parties. Such mechanisms have to be designed in a way that they give rational self-interested agents no incentives for insincere behavior. We introduce an arbiter as third party that resolves conflicting bargaining situations between the agents. To achieve non-manipulative agent behavior, we investigate three arbitration protocols that avoid different forms of manipulations and show how each trades net efficiency for robustness against manipulations. We describe the applicability of the protocols in bilateral bargaining situations and, analyze their robustness against manipulations analytically and by simulations. We compare the protocols with Nashs arbitration1 and the Groves-Clarke tax2 and characterize situations in which our protocols are superior.

Skalierbare Verarbeitung von XML mit Infonyte-DB

The emerging penetration of IT architectures with XML results in increasing XML data volumes. Available tools often fail in realizing scalable XML processing for large XML data volumes. Infonyte-DB, a product of Infonyte GmbH, is a high performance XML kernel that economizes on system resources and allows the processing of large XML data volumes.

The Transcoop Transaction Model

This chapter describes the TRANSCOOP cooperative transaction model CoACT, and its underlying paradigm of cooperative work. As motivated in Chapter 4 new application areas of the transaction concept impose new requirements on transaction models. In all of the discussed application areas there is a need to support the cooperation of human actors engaged in common tasks and working towards a common goal. a transaction model supporting cooperation should make the sharing and exchange of information among co-workers as natural as possible while still preserving a notion of consistency.

Global nested transaction management for ODMG-compliant multi-database systems

Object technology has received considerable attention in the re cent years for the integration of various local data sources in a multi-database system (MDBS). An object-oriented data model like ODMG-93 can serve as the canonical data model for the global layer in the MDBS. The ODMG-93 standard defines a closed nested ACID transaction model without intra-transaction parallelism. Although the nested transaction model provides special support for distributed computing enviromnents, the implications of its usage as a global transaction model for MDBS have so far not been examined. In this paper, we present a simple and practical method to implement global nested transaction management for ODMGcompliant multi-database systems. The main contribution of our work is the adaption of the ticket method to achieve global serializability for global nested transactions that conform to ODMG. Our approach is also applicable to OMG’s common object request broker architecture. We have successfully implemented our global nested transaction model within the IRO-DB multi-database system.

Cooperative Data Management and its Application to Mobile Computing

Mobile computing and workgroup computing are emerging technologies which have so far been treated independently. Current approaches to support cooperative work neglect the special characteristics of mobile environments like limited bandwidth or temporary disconnection. On the other hand, approaches to support disconnected operation rely on the assumption that the degree of data-sharing is low which is obviously not appropriate for cooperative work. In this paper, we utilize the COACT cooperative transaction model to provide support for parallel activities in mobile environments. We present a system architecture that is able to cope with the special characteristics of mobile environments and a formal framework for the consistent information exchange between mobile users. The paper shows how the COACT history merge algorithm reduces conflicts by exploiting operation semantics and offering consistent sequences of operations. We believe that our new approach is a viable solution to the growing demand for cooperation in mobile environments.