Contributions in Merlin

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One of the key challenges in peer-to-peer networks is the design of incentives to encourage peers to share their resources. Incentives are necessary in order to exploit the full potential of these systems. The tit-for-tat incentive scheme, as used in BitTorrent for example, has proven to be a successful approach in P2P file sharing systems, where peers have direct relations and share the same kind of resources. However, in P2P systems where different kind of resources are shared between peers with non-direct relations, the design of incentives remains a challenge. In this paper, a large-scale, fully decentralized P2P collaboration network is shown, where peers share not only bandwidth and storage space, but also contribute by editing articles and voting for or against changes. A new incentive scheme is proposed which supports non-direct relations and provides incentives for sharing different kind of resources. The incentive scheme is based on a reputation system that assigns a reputation value to every peer reflecting its previous behavior in the network. Based on this value, the service level is differentiated, i.e. the higher a peer's reputation the better the quality of service it can get from the network. The service differentiation has been analyzed and simulated with rational, irrational and altruistic peers based on game theory concepts.

The following topics were dealt with: provisioning of bandwidth on demand; resource allocation; multi-domain optical networks; network pricing; bandwidth trading; virtual network topology control; bandwidth reservation network and GMPLS signalling.

Peer-to-peer (P2P) systems show numerous advantages over centralized systems, such as load balancing, scalability, and fault tolerance, and they require certain functionality, such as search, repair, and message and data transfer. In particular, structured P2P networks perform an exact search in logarithmic time proportional to the number of peers. However, keyword similarity search in a structured P2P network remains a challenge. Similarity search for service discovery can significantly improve service management in a distributed environment. As services are often described informally in text form, keyword similarity search can find the required services or data items more reliably. This paper presents a fast similarity search algorithm for structured P2P systems. The new algorithm, called P2P fast similarity search (P2PFastSS), finds similar keys in any distributed hash table (DHT) using the edit distance metric, and is independent of the underlying P2P routing algorithm. Performance analysis shows that P2PFastSS carries out a similarity search in time proportional to the logarithm of the number of peers. Simulations on PlanetLab confirm these results and show that a similarity search with 34,000 peers performs in less than three seconds on average. Thus, P2PFastSS is suitable for similarity search in large-scale network infrastructures, such as service description matching in service discovery or searching for similar terms in P2P storage networks.

Despite the surge of interest in data reduction techniques over the past years, no method has been proposed to date that can always achieve approximation quality preferable to that of the optimal plain histogram for a target error metric. In this paper, we introduce the Lattice Histogram: a novel data reduction method that discovers and exploits any arbitrary hierarchy in the data, and achieves approximation quality provably at least as high as an optimal histogram for any data reduction problem. We formulate LH construction techniques with approximation guarantees for general error metrics. We show that the case of minimizing a maximum-error metric can be solved by a specialized, memory-sparing approach; we exploit this solution to design reduced-space heuristics for the generalerror case. We develop a mixed synopsis approach, applicable to the space-efficient high-quality summarization of very large data sets. We experimentally corroborate the superiority of LHs in approximation quality over previous techniques with representative error metrics and diverse data sets.

This paper discusses the design and first deployment experiences of an interactive large-display workspace for face-to-face travel consultancy. The stickiness of client preferences, the asymmetry of information about the solution space and the emotional colouring of client choices, make this complex cooperative process difficult to perform. To support such collocated consultancies we propose a large-display system providing a shared visualization of information resources that can be manipulated jointly by both parties. The use of natural touch interaction and multimedia resources furthers emotional involvement of the user. Results of a preliminary evaluation suggest that such a large-display workspace can greatly improve the cooperation process and both customer and agent satisfaction.

We present AceWiki, a prototype of a new kind of semantic wiki using the controlled natural language Attempto Controlled English (ACE) for representing its content. ACE is a subset of English with a restricted grammar and a formal semantics. The use of ACE has two important advantages over existing semantic wikis. First, we can improve the usability and achieve a shallow learning curve. Second, ACE is more expressive than the formal languages of existing semantic wikis. Our evaluation shows that people who are not familiar with the formal foundations of the Semantic Web are able to deal with AceWiki after a very short learning phase and without the help of an expert.

With the fast pace of globalization and knowledge-driven economy, the notion of trust in intra- and/or trans-organizational relations has attracted enormous attention both in academic research and business practices. It has been recognized that trust as a central mechanism within and between organizations plays a crucial role for economic performance. Trust relationship at personal levels is particular important in an environment where the institutional foundations for trust are still underdeveloped. China is commonly regarded as a country with low levels of institution-based trust. As a consequence, the quality of business relations, economic transactions and strategic alliances are strongly dependent on the degree of trust at personal levels. The objective of this study is to contribute to our understanding of trust relationships between hierarchies within Chinese organizational settings. In this paper, we present our empirical research on trust at personal levels carried out in a large Chinese state-owned enterprise. Three hypotheses that characterise the subordinate’s trust in the superior are developed and tested. Based on the statistical evaluations from 1216 samples collected, factors that influence the truster’s propensity to trust are outlined. The determinants for the trustee’s trustworthiness are analysed. In conclusion, we emphasis that further research on trust at personal levels in different enterprises, and trust at organizational levels are needed in order to draw a generalised picture on trust relationships in organizational settings.

We propose a valuation method for financial assets subject to default risk, where investors cannot observe the state variable triggering the default but observe a correlated price process. The model is sufficiently general to encompass a large class of structural models and can be seen as a generalization of the model of Duffie and Lando (Econometrica 69:633–664, [2001]). In this setting we prove that the default time is totally inaccessible in the market’s filtration and derive the conditional default probabilities and the intensity process. Finally, we provide pricing formulas for default-sensitive claims and illustrate in particular examples the shapes of the credit spreads.