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9th European Conference on Web Services, ECOWS 2011

作者： Müller, Jens Böhm, Klemens Karlsruhe Institute of Technology Institute for Program Structures and Data Organization 76131 Karlsruhe Germany

ISBN: (纸本)9780769545363

Business-process-management (BPM) systems are increasingly used in service-oriented architectures (SOA), coordinating activities of web services and of human actors. The openness and flexibility of SOA causes new challenges regarding security of business processes. This is because they have to deal with unexpected situations at run time. Respective solutions must be inherent to a BPM system (BPMS). Process implementers must explicitly model different security aspects of business processes, and the BPMS must combine them with run-time context to enforce security. However, existing BPMS do not address security issues in a way that is sufficiently broad. Thus, extensions are necessary, and they should integrate existing technology. The core contribution of this paper is to propose how to extend the WfMC reference architecture for BPMS to accomplish this, having identified different design alternatives. The resulting architecture is generic and integrates with existing SOA technologies like federated identity management. It is modular, making adaptations relatively easy. This has been hard to achieve because security aspects concern the entire system. Finally, our architecture can be used to implement the various business process security modelling approaches that have been presented in the literature. © 2011 IEEE.

关键词： Web services

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Performance certification of software components

Performance certification of software components

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作者： Burger, Erik Reussner, Ralf Software Design and Quality Institute for Program Structures and Data Organization Faculty of Informatics Germany

Non-functional properties of software should be specified early in the development process. In a distributed process of software development, this means that quality requirements must be made explicit in the specification, and the developing party of a commissioned component needs to deliver not only the implemented component, but also a description of its non-functional properties. Based on these artefacts, a conformance check guarantees that the implemented component fulfills the performance requirements. We extend the notion of model refinement to non-functional properties of software and propose a refinement calculus for conformance checking between abstract performance descriptions of components. The calculus is based on a refinement notion that covers the performance-relevant aspects of components. The approach is applied to the Palladio Component Model as a description language for performance properties of components. © 2011 Elsevier B.V. All rights reserved.

关键词： Calculations

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Evolving Cooperation through Reciprocity Using a Centrality-Based Reputation System

Evolving Cooperation through Reciprocity Using a Centrality-...

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IEEE WIC ACM International Conference on Web Intelligence (WI)

作者： Christian Hutter Raphael Lorch Klemens Bohm Institute for Program Structures and Data Organization Karlsruhe Institute of Technology Germany

Reciprocity is the basis for cooperation between agents in settings without payments. Research has shown that cooperation through reciprocity can emerge if reputation information is available. Various reputation mechanisms have been proposed, which are either not efficient or vulnerable to errors in perception. We propose a reputation mechanism based on centrality, which outperforms existing mechanisms in terms of efficiency and robustness. To evaluate our approach, we first conduct numerical simulations where we analyze different centrality measures. We then use the `winning' measure in a behavioral experiment to evaluate its effectiveness with real users. Our results are that distance-based centrality measures are most suitable for multi-agent systems. Furthermore, humans adopt strategies based on centrality for sending requests, but not for processing them.

关键词： Measurement Games Robustness History Stability analysis Humans Multiagent systems

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Cooperation through reciprocity in multiagent systems: an evolutionary analysis 11

Cooperation through reciprocity in multiagent systems: an ev...

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The 10th International Conference on Autonomous Agents and Multiagent Systems - Volume 1

作者： Christian Hütter Klemens Böhm Institute for Program Structures and Data Organization Karlsruhe Institute of Technology Germany

ISBN: (纸本)9780982657157

The Service Game is a model for reciprocity in multiagent systems. Here, agents interact repeatedly by requesting and providing services. In contrast to existing models where players are matched randomly, players of the Service Game may choose with whom they play. The rationale behind provider selection is to choose a provider that is likely to perform a task as desired. We develop a formal model for provider selection in the Service Game. An evolutionary process based on a genetic algorithm allows us to incorporate notions of bounded rationality, learning, and adaptation into the analysis of the game. We conduct a series of experiments to study the evolution of strategies and the emergence of cooperation. We show that cooperation is more expensive with provider selection than with random matching. Further, populations consisting of discriminators and defectors form a bistable community.

关键词： agent cooperation evolution formal model social simulation

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The Architecture of a Secure Business-Process-Management System in Service-Oriented Environments

The Architecture of a Secure Business-Process-Management Sys...

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European Conference on Web Services (ECOWS)

作者： Jens Muller Klemens Bohm Institute for Program Structures and Data Organization Karlsruhe Institute of Technology Karlsruhe Germany

关键词： Context Service oriented architecture Humans Business Authorization

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A study of the impact of structure on cooperation in networks

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Web Intelligence and Agent Systems 2011年第3期9卷 269-288页

作者： Schosser, Stephan Böhm, Klemens Vogt, Bodo Institute of Economic Theory and Statistics Karlsruhe Institute of Technology Zirkel 2 76128 Karlsruhe Germany Institute for Program Structures and Data Organization Karlsruhe Institute of Technology Am Fasanengarten 5 76131 Karlsruhe Germany Faculty of Economics Empirical Economics Otto-von-Guericke Universität Magdeburg Universitätsplatz 2 39106 Magdeburg Germany

The concern of this paper is that nodes in a distributed system cooperate. We demonstrate that adding structure to such systems can help to induce cooperation. 'Adding structure' means bounding the number of nodes a node can directly interact with - if two unconnected nodes wish to interact, they have to do so via a chain of intermediaries which are connected. To validate our claim, we analyze one specific system where structure has been added. Different methods exist for such analyses: Economists use behavioral experiments to study human behavior. Computer scientists rely on simulations, to obtain results that are robust and scalable. Both use game theory to arrive at formal results. Each approach in isolation has its disadvantages: Behavioral experiments do not allow analyzing many different combinations of parameter values and do not scale well. Game theory supports analyzing system equilibria, but may result in complex or even unsolvable models, in particular when considering system dynamics. Simulations rely on the intuition of the system designer - this is hazardous in strategic settings. We pursue a combination of these approaches and show that the degree of cooperation in our setting is high. More specifically, after having shown with behavioral experiments that humans tend to use cut-off strategies, we translate the strategies used into a game theoretic model and show that they yield an efficient equilibrium. Simulations show that the system reaches this equilibrium given random start populations if the rate of free riders is low. We conclude by saying how our work affects the design of distributed systems from a computer science perspective. © 2011 - IOS Press and the authors. All rights reserved.

关键词： Game theory

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Impact assessment in public policy: Towards a Web 2.0 application

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Information Polity 2010年第1-2期15卷 33-50页

作者： Heidinger, Clemens Buchmann, Erik Böhm, Klemens Karlsruhe Institute of Technology (KIT) Institute for Program Structures and Data Organization (IPD) 76131 Karlsruhe Am Fasanengarten 5 Germany

Impact assessment (IA) is a key method for the legislator to evaluate policies, norms or regulations currently under development. Experts use IA to gather and analyze input from many individuals to obtain clear problem statements, estimations regarding policies etc., and use this information to compare policy alternatives. Currently, the opinions, expertise etc. gathered for IA need to be structured by hand. Thus, the analysis steps of IA are time-consuming, and IA does not scale with the number of persons involved. In this paper, we introduce a collaborative approach for IA. Based on a Web 2.0 architecture, we let a community of individuals derive the potential, downsides and design alternatives of policies collaboratively. Our approach guides individuals through the process of creating structured input. Our approach is fully implemented, and we have evaluated it together with legal experts by means of a small pilot study. Our evaluation indicates that the acceptance of a Web 2.0-based IA application strongly depends on the user interface. More profoundly, it shows that our approach can be an important tool for future IA. © 2010-IOS Press and the authors.

关键词： Impact assessment Web 2.0 Application

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SONAR: Towards user-centric social network analysis and visualization

SONAR: Towards user-centric social network analysis and visu...

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2010 IEEE/WIC/ACM International Conference on Web Intelligence, WI 2010

作者： Hütter, Christian Hartmann, Björn-Oliver Böhm, Klemens Heistermann, Till Kohlmeyer, Kevin-Simon Reckling, Reno Reiche, Martin Parra, David Soria Institute for Program Structures and Data Organization Karlsruhe Institute of Technology Germany MAYFLOWER GmbH München Germany

ISBN: (纸本)9780769541914

Social network analysis (SNA) has attracted a lot of attention over the past years. Existing tools for SNA do not allow a user-centric analysis of the social neighborhood, i.e., the subgraph of the user's friends and friends of a friend. In this paper, we introduce SONAR, an open source Web application for user-centric SNA. Its extensible architecture and flexible data model allows developers to embed SONAR directly into social networking websites. A performance evaluation shows that our application scales well with the number of users and adds only minimal overhead to the SNA algorithms. © 2010 IEEE.

关键词： Social networking (online)

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Strategic provider selection in a policy-based helping scenario

Strategic provider selection in a policy-based helping scena...

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12th IEEE Conference on Commerce and Enterprise Computing, CEC 2010

作者： Hütter, Christian Yue, Jing Zhi Von Der Weth, Christian Böhm, Klemens Institute for Program Structures and Data Organization Karlsruhe Institute of Technology Germany School of Computer Engineering Nanyang Technological University Singapore

ISBN: (纸本)9780769542287

In service-oriented computing, software agents interact by requesting and providing services. Since providing a service incurs cost, uncooperative behavior dominates in the absence of an incentive mechanism. An economic model that describes interactions between individuals is the Helping. Game. There, pairs of requester and provider are randomly matched. In various real-world applications in turn, several providers offer similar services, and requesters have a choice of providers. The rationale behind strategic provider selection is to choose the provider that is most likely to perform the task as desired. The results from existing studies of the Helping Game are not directly applicable to settings with provider selection. To analyze how strategic provider selection affects the efficiency of enterprise systems, we have designed and carried out an experimental study. Our results show that cooperative participants receive significantly more requests than uncooperative ones, making cooperation expensive. We conclude that system designers must incentivize requesters to balance their tasks between providers. © 2010 IEEE.

关键词： Software agents

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Stochastic performance analysis and capacity planning of publish/subscribe systems 10

Stochastic performance analysis and capacity planning of pub...

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4th ACM International Conference on Distributed Event-Based Systems, DEBS 2010

作者： Schröter, Arnd Mühl, Gero Kounev, Samuel Parzyjegla, Helge Richling, Jan Communication and Operating Systems Group Berlin University of Technology Germany Architecture of Application Systems University of Rostock Germany Institute for Program Structures and Data Organization Karlsruhe Institute of Technology Germany

ISBN: (纸本)9781605589275

Publish/subscribe systems are used increasingly often as a communication mechanism in loosely-coupled distributed applications. With their gradual adoption in mission critical areas, it is essential that systems are subjected to a rigorous performance analysis before they are put into production. However, existing approaches to performance modeling and analysis of publish/subscribe systems suffer from many limitations that seriously constrain their practical applicability. In this paper, we present a set of generalized and comprehensive analytical models of publish/subscribe systems employing different peer-to-peer and hierarchical routing schemes. The proposed analytical models address the major limitations underlying existing work in this area and are the first to consider all major performance-relevant system metrics including the expected broker and link utilization, the expected notification delay, the expected time required for new subscriptions to become fully active, as well as the expected routing table sizes and message rates. To illustrate our approach and demonstrate its effectiveness and practicality, we present a case study showing how our models can be exploited for capacity planning and performance prediction in a realistic scenario. © 2010 ACM.

关键词： Analytical models

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