Sven Seuken

Hidden markets: UI design for a P2P backup application

The Internet has allowed market-based systems to become increasingly pervasive. In this paper we explore the role of user interface (UI) design for these markets. Different UIs induce different mental models which in turn determine how users understand and interact with a market. Thus, the intersection of UI design and economics is a novel and important research area. We make three contributions at this intersection. First, we present a novel design paradigm which we call hidden markets. The primary goal of hidden markets is to hide as much of the market complexities as possible. Second, we explore this new design paradigm using one particular example: a P2P backup application. We explain the market underlying this system and provide a detailed description of the new UI we developed. Third, we present results from a formative usability study. Our findings indicate that a number of users could benefit from a market-based P2P backup system. Most users intuitively understood the give & take principle as well as the bundle constraints of the market. However, the pricing aspect was difficult to discover/understand for many users and thus needs further investigation. Overall, the results are encouraging and show promise for the hidden market paradigm.

Market design & analysis for a P2P backup system

In this paper we take the problem of a market-based P2P backup application and carry it through market design, to implementation, to theoretical and experimental analysis. While the long-term goal is an open market using real money, here we consider a system where monetary transfers are prohibited. We first describe the design of the P2P resource exchange market and the UI we developed. Second, we prove theorems on equilibrium existence and uniqueness. Third, we prove a surprising impossibility result regarding the limited controllability of the equilibrium and show how to address this. Fourth, we present a price update algorithm that uses daily supply and demand information to move prices towards the equilibrium and we provide a theoretical and experimental convergence analysis. The market design described in this paper is already implemented as part of a Microsoft research project on P2P backup systems and an alpha version of the software has been successfully tested.

An axiomatic approach to characterizing and relaxing strategyproofness of one-sided matching mechanisms

We study one-sided matching mechanisms where agents have vNM utility functions and report ordinal preferences. We first show that in this domain strategyproof mechanisms are characterized by three intuitive axioms: swap monotonicity, upper invariance, and lower invariance. Our second result is that dropping lower invariance leads to an interesting new relaxation of strategyproofness, which we call partial strategyproofness. In particular, we show that mechanisms are swap monotonic and upper invariant if and only if they are strategyproof on a restricted domain where agents have sufficiently different valuations for different objects. Furthermore, we show that this domain restriction is maximal and use it to define a single-parameter measure for the degree of strategyproofness of a manipulable mechanism. We also provide an algorithm that computes this measure. Our new partial strategyproofness concept finds applications in the incentive analysis of non-strategyproof mechanisms, such as the Probabilistic Serial mechanism, different variants of the Boston mechanism, and the construction of new hybrid mechanisms.

Market User Interface Design

Electronic markets are becoming more and more pervasive but a remaining challenge is to develop user interfaces (UIs) to promote efficient market outcomes. This can be a challenge in markets with a large number of choices, yet traditional economic models do not consider that humans have cognitive costs, bounded time for decision making, and bounded computational resources. Behavioral economists have begun to explore the cognitive costs associated with decision making in complex environments [1], but until now, the market design community has largely ignored the intersection of market design and UI design. Gajos et al. [2] have designed a system that can automatically generate UIs that are adapted to a person’s devices, tasks, and abilities, but not for market domains. In our own previous work [3], we have introduced the goal of designing simple and easy-to-use interfaces for electronic markets, in particular for domains where users repeatedly make decisions of small individual value. In this work, we propose a new research agenda on “market user interfaces” and present an experimental study of the market UI design space. A market UI can best be defined via two questions: first, what information is displayed to the user? Second, what choices/how many choices are offered to the user? Our goal is to design market UIs that make the decision-making task easier for the users and lead to more efficient market outcomes. Thus, the research question we want to answer is: what is the optimal market UI given that users have cognitive costs?

Handling interdependent values in an auction mechanism for bandwidth allocation in tactical data networks

We consider a tactical data network with limited bandwidth, in which each agent is tracking objects and may have value for receiving data from other agents. The agents are self-interested and would prefer to receive data than share data. Each agent has private information about the quality of its data and can misreport this quality and degrade or otherwise decline to share its data. The problem is one of interdependent value mechanism design because the value to one agent for the broadcast of data on an object depends on the quality of the data, which is privately known to the sender. A recent two-stage mechanism due to Mezzetti (2004) can be modified to our setting. Our mechanism achieves efficient bandwidth allocation and provides incentive compatibility by conditioning payments on the realized value for data shared between agents.

EMIKA system: architecture and prototypic realization

Life critical applications in hospital environments have got special requirements concerning IT support: a real-time cooperation is necessary to ensure a continuous workflow. This article describes the prototypic realization of the EMIKA project, a real-time controlled mobile information system for clinical applications. The EMIKA architecture is comprised of three layers: first of all, the communication layer provides wireless device interaction. Secondly, the middleware layer establishes a common service platform for automated service provision and access. Finally, the application layer implements a multi-agent system for the real-time coordination needed for a self-organizing patient logistics environment.

Finding Clearing Payments in Financial Networks with Credit Default Swaps is PPAD-complete

We consider the problem of clearing a system of interconnected banks that have been exposed to a shock on their assets. Eisenberg and Noe (2001) showed that when banks can only enter into simple debt contracts with each other, then a clearing vector of payments can be computed in polynomial time. In this paper, we show that the situation changes radically when banks can also enter into credit default swaps (CDSs), i.e., financial derivative contracts that depend on the default of another bank. We prove that computing an approximate solution to the clearing problem with sufficiently small constant error is PPAD-complete. To do this, we demonstrate how financial networks with debt and CDSs can encode arithmetic operations such as addition and multiplication. Our results have practical impact for network stress tests and reveal computational complexity as a new concern regarding the stability of the financial system.

Challenges of Source Selection in the WoD

Federated querying, the idea to execute queries over several distributed knowledge bases, lies at the core of the semantic web vision. To accommodate this vision, SPARQL provides the SERVICE keyword that allows one to allocate sub-queries to servers. In many cases, however, data may be available from multiple sources resulting in a combinatorially growing number of alternative allocations of subqueries to sources. Running a federated query on all possible sources might not be very lucrative from a user’s point of view if extensive execution times or fees are involved in accessing the sources’ data. To address this shortcoming, federated join-cardinality approximation techniques have been proposed to narrow down the number of possible allocations to a few most promising (or results-yielding) ones.

Sharing in BitTorrent Can Be Rational

Consider a game played by two mountaineers climbing a mountain.Both are only interested in attaining the summit and can only reach it with help from the other. Over an infinite number of discrete periods they play a symmetric simultaneous game where they may either help the other a fixed distance up the mountain at some cost, or do nothing. Can these mountaineers climb their mountain?

Market Design for a P2P Backup System

Peer-to-peer (P2P) backup systems are an attractive alternative to server-based systems because the immense costs of large data centers can be saved by using idle resources on millions of private computers instead. This paper presents the design and theoretical analysis of a market for a P2P backup system. While our long-term goal is an open resource exchange market using real money, here we consider a system where monetary transfers are prohibited. A user who wants to backup his data must in return supply some of his resources (storage space, upload and download bandwidth) to the system.We propose a hybrid P2P architecture where all backup data is transferred directly between peers, but a dedicated server coordinates all operations and maintains meta-data. We achieve high reliability guarantees while keeping our data replication factor low by adopting sophisticated erasure coding technology (cf., [2]).