Contributions in Merlin

Software becomes more and more complex. For this reason we need other possibilities to understanding large software systems. CocoViz want to vizualize the code with common metaphors for an intuitive understanding of software structures and evolution. The work show an implementation on .NET that allow you to filter the metric data and visualize shapes in a 3D world. Thereby well-designed visual object represent a well-designed class. This application help to remedy deficiencies in a intuitive form.

The services offered by the governmental public sector are currently changing: Apart from shifting the focus from service-oriented to citizen-oriented services, a growing amount of administrative activities are supported by information technology in the context of E-Government. A personalized advisory service in different circumstances of life should now be offered as a part of citizen-oriented administrative services. By means of information technology the advisory services should be able to respond to the needs of individuals and adapt better to their wishes. In this paper „having a baby“ has been chosen as an examplary circumstance in life, which symbolically stands for a number of other situations in a citizen’s lifetime. This thesis presents one possibility of a software application to support the advisory service for the citizen in the situation of „having a baby“. Among other factors, it facilitates the advisory work by an integration and clearly arranged presentation of information taken from internal and external sources. Besides the high adaptability of advisory services, it emphasises a close and active collaboration between a citizen and an advisor. Based on an analysis of the working conditions, requirements have been collected and their specifications stated. This has resulted in a structured design- and advisory-concept. A prototype of a tool for citizen-advisory services has been implemented and in conclusion evaluated in some trial advisory sessions. These tests have been executed in situations designed as realistically as possible. The results show that the implemented, tailor-made application as well as the tested form of the advisory service presented in this thesis have appealed to both advisors and citizens.

Despite the importance of mutualism as a key ecological process, its persistence in nature is difficult to explain since the existence of exploitative, ""cheating"" partners that could erode the interaction is common. By analogy with the proposed policing strategy stabilizing intraspecific cooperation, host sanctions against non-N(2) fixing, cheating symbionts have been proposed as a force stabilizing mutualism in legume-Rhizobium symbiosis. Following this proposal, penalizations would include decreased nodular rhizobial viability and/or early nodule senescence in nodules occupied by cheating rhizobia. In this work, we analyse the stability of Rhizobium-legume symbiosis when non-fixing, cheating strains are present, using an experimental and modelling approach. We used split-root experiments with soybean plants inoculated with two rhizobial strains, a cooperative, normal N(2) fixing strain and an isogenic non-fixing, ""perfect"" cheating mutant derivative that lacks nitrogenase activity but has the same nodulation abilities inoculated to split-root plants. We found no experimental evidence of functioning plant host sanctions to cheater rhizobia based on nodular rhizobia viability and nodule senescence and maturity molecular markers. Based on these experiments, we developed a population dynamic model with and without the inclusion of plant host sanctions. We show that plant populations persist in spite of the presence of cheating rhizobia without the need of incorporating any sanction against the cheater populations in the model, under the realistic assumption that plants can at least get some amount of fixed N(2) from the effectively mutualistic rhizobia occupying some nodules. Inclusion of plant sanctions leads to the unrealistic effect of ultimate extinction of cheater strains in soil. Our simulation results are in agreement with increasing experimental evidence and theoretical work showing that mutualisms can persist in presence of cheating partners.

In den letzten Jahren ist wieder der Ruf nach mehr Praxisrelevanz der Betriebswirtschafts- bzw. Managementlehre laut geworden. Unter relevanter Forschung wird dabei in der Regel eine Forschung verstanden, die letztlich zu instrumentellem Wissen führt, das in der Unternehmenspraxis einsetzbar ist. Eine solche, auf Entwicklung instrumentellen Wissens ausgerichtete Forschung wird auch als technologische Forschung bezeichnet – im Gegensatz zur theoretischen Forschung. Während es in der theoretischen Forschung um „Aufklärung“ geht, d.h. um Erklärung von Zusammenhängen, geht es bei der technologischen Forschung um „Steuerung“ bzw. „Gestaltung“. Theoretische Aussagen sind Aussagen über Ursache-Wirkungs-Beziehungen, technologische Aussagen betreffen dagegen Mittel-Zweck-Beziehungen. In diesem Beitrag wollen wir darlegen, dass theoretische und technologische Aussagenzusammenhänge zwei eigenständige Forschungszweige darstellen und damit die Notwendigkeit erwächst, eine eigene Methodologie technologischer Aussagenzusammenhänge zu entwerfen. Es sollen Ansatzpunkte aufgezeigt werden, wie eine solche Methodologie technologischer Aussagenzusammenhänge aussehen kann. Dabei wird auch der Frage nach der Wissenschaftlichkeit technologischer Forschung nachzugehen sein.

We propose a conceptual framework based on input-process-output models adapted from traditional group research for the systematic analysis of virtual teamwork. A research agenda contains a list of research questions that will be investigated in a controlled field study in the context of “The ShanghAI Lectures”, a global teaching and international student collaboration project. The research questions are formulated regarding processes and outcomes of global virtual teamwork and focus on usability and sociability issues in collaborative work in 3D virtual environments. An operational framework is provided for collecting the relevant data in a structured manner by using qualitative and quantitative process measures of group behavior.

This paper shows that the framework proposed by Barberis and Huang (2009) to incorporate narrow framing and loss aversion in dynamic models of portfolio choice and asset pricing can be extended to also account for probability weighting and a value function which is convex on losses and concave on gains. We show that the addition of probability weighting and a convex-concave value function reinforces previous applications of narrow framing and cumulative prospect theory to explain the stock market non-participation puzzle and the equity premium puzzle. Moreover, we show that a convex-concave value function generates new wealth effects that are consistent with empirical observations on stock market participation.

We present a novel geographical routing scheme for spontaneous wireless mesh networks. Greedy geographical routing has many advantages, but suffers from packet losses occurring at the border of voids. In this paper, we propose a flexible greedy routing scheme that can be adapted to any variant of geographical routing and works for any connectivity graph, not necessarily Unit Disk Graphs. The idea is to reactively detect voids, backtrack packets, and propagate information on blocked sectors to reduce packet loss. We also propose an extrapolating algorithm to reduce the latency of void discovery and to limit route stretch. Performance evaluation via simulation shows that our modified greedy routing avoids most of packet losses.

We present a new access control mechanism for P2P networks with distributed enforcement, called P2P Access Control System (PACS). PACS enforces powerful access control models like RBAC with administrative delegation inside a P2P network in a pure P2P manner, which is not possible in any of the currently used P2P access control mechanisms. PACS uses client-side enforcement to support the replication of confidential data. To avoid a single point of failure at the time of privilege enforcement, we use threshold cryptography to distribute the enforcement among the participants. Our analysis of the expected number of messages and the computational effort needed in PACS shows that its increased flexibility comes with an acceptable additional overhead.

This paper presents the design and theoretical analysis of a P2P resource exchange market, a novel application of mar- kets to the domain of P2P backup. While the long-term goal is an open market using real money, here we consider a system where monetary transfers are prohibited. We ¯rst describe the design of the market and the user interface we developed. Second, we prove theorems on equilibrium ex- istence and uniqueness. Third, we present a price update algorithm that uses daily supply and demand information to move prices towards the equilibrium. The market design described in this paper is already implemented as part of a Microsoft research project on P2P backup systems and an internal alpha version of the software has been released. We will thus complement the theoretical analysis with discus- sions of implementation challenges that arise in practice.

The recent real estate bubble was fuelled by non-risk-adjusted lending policies, low interest rates, and complex finance vehicles. Mortgage-backed securities (MBS) played a crucial role in the crisis. These vehicles were praised as liquid capital market instruments that allowed mortgage lenders to replenish their funds, which could then be used for additional origination activities. However, in some forms, securitized mortgage pools are highly complex and hard to price. It turned out that MBS were not able to deal with the risks of the real estate market appropriately. The painful burst of the real estate bubble highlights the urgent need for instru-ments that provide more transparency and allow better mitigating of both house price and commercial property risk. Property derivatives, currently emerging in the US and the UK, address real estate prices directly and make them more transparent. Thus, they facilitate a more efficient risk allocation. We illustrate the possibilities and limitations of property derivatives with respect to the current subprime crisis.