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    <title>OPUS 4 Latest Documents RSS Feed</title>
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    <link>http://opus4.kobv.de/opus4-bamberg/index/index/</link>
    <pubDate>Fri, 21 Sep 2012 09:21:12 +0200</pubDate>
    <lastBuildDate>Fri, 21 Sep 2012 09:21:12 +0200</lastBuildDate>
    <item>
      <title>Betsy - A BPEL Engine Test System</title>
      <link>http://opus4.kobv.de/opus4-bamberg/frontdoor/index/index/docId/649</link>
      <description>More than five years have passed since the final release of the long-desired OASIS standard of a process language for web service orchestration, the Web Services Business Process Execution Language (BPEL). The aim of this standard is to establish a universally accepted orchestration language that forms a core part of current service-oriented architectures and, because of standardisation, avoids vendor lock-in. High expectations, in academia and practice alike, have been set on it. By now, several fully conformant and highly scalable engines should have arrived in the market. The perception of many however, is that standard conformance in current engines is far from given. It is our aim to shed light on this situation. In this study, we present the tool betsy, a BPEL Engine Test System that allows for a fully-automatic assessment of the standard conformance of a given BPEL engine. We use it to examine the five most important open source BPEL engines available today. Betsy comes with a large set of engineindependent conformance test cases for assessing BPEL standard conformance. This enables us to give a view of the state of the art in BPEL support.</description>
      <author>Simon Harrer; Jörg Lenhard</author>
      <category>report</category>
      <guid>http://opus4.kobv.de/opus4-bamberg/frontdoor/index/index/docId/649</guid>
      <pubDate>Fri, 21 Sep 2012 09:21:12 +0200</pubDate>
    </item>
    <item>
      <title>Visibility in Information Spaces and in Geographic Environments. Post-Proceedings of the KI'11 Workshop (October 4th, 2011, TU Berlin, Germany)</title>
      <link>http://opus4.kobv.de/opus4-bamberg/frontdoor/index/index/docId/326</link>
      <description>In the post-proceedings of the Workshop "Visibility in Information Spaces and in Geographic Environments" a selection of research papers is presented where the topic of visibility is addressed in different contexts. Visibility governs information selection in geographic environments as well as in information spaces and in cognition. The users of social media navigate in information spaces and at the same time, as embodied agents, they move in geographic environments. Both activities follow a similar type of information economy in which decisions by individuals or groups require a highly selective filtering to avoid information overload. In this context, visibility refers to the fact that in social processes some actors, topics or places are more salient than others. Formal notions of visibility include the centrality measures from social network analysis or the plethora of web page ranking methods. Recently, comparable approaches have been proposed to analyse activities in geographic environments: Place Rank, for instance, describes the social visibility of urban places based on the temporal sequence of tourist visit patterns. The workshop aimed to bring together researchers from AI, Geographic Information Science, Cognitive Science, and other disciplines who are interested in understanding how the different forms of visibility in information spaces and geographic environments relate to one another and how the results from basic research can be used to improve spatial search engines, geo-recommender systems or location-based social networks.</description>
      <author>Andreas Henrich; Christoph Schlieder; Ute Schmid; Inessa Seifert; Bertram Saendig; Dominik Kremer; Peter Grossman; Markus Wachter; Marius Raab; Claus-Christian Carbon; Stella J. Faerber</author>
      <category>conferenceobject</category>
      <guid>http://opus4.kobv.de/opus4-bamberg/frontdoor/index/index/docId/326</guid>
      <pubDate>Fri, 23 Dec 2011 11:37:14 +0100</pubDate>
    </item>
    <item>
      <title>A Pattern-based Analysis of WS-BPEL and Windows Workflow</title>
      <link>http://opus4.kobv.de/opus4-bamberg/frontdoor/index/index/docId/283</link>
      <description>Orchestration languages are of paramount importance for building composite services in service-oriented architectures. Pattern-based analysis is a method that allows to determine the expressiveness of existing process languages and serves as a means of comparison between different languages. The aim of this study is the analysis and comparison of important languages for building Web Services-based orchestrations, as well as the improvement of the method of pattern-based analysis. The predominant orchestration language today is the Web Services Business Process Execution Language (WS-BPEL) 2.0. This language is a standard that has been implemented by several companies and projects, such as the OpenESB BPEL Service Engine. An additional language is Windows Workflow 4 that is shipped by Microsoft as part of the .NET framework. There are various aspects, represented by pattern catalogs, for which existing languages can be analyzed. This study suggests a methodology for ordering existing pattern catalogs according to their importance for a selected problem domain which is Business-to-Business Integration. It furthermore presents an extensive evaluation of the languages at hand and assesses the degree of support they provide for several of the most important pattern catalogs. These catalogs are the workflow control-flow patterns, the service interaction patterns, the change patterns and the time patterns.</description>
      <author>Jörg Lenhard</author>
      <category>report</category>
      <guid>http://opus4.kobv.de/opus4-bamberg/frontdoor/index/index/docId/283</guid>
      <pubDate>Mon, 27 Jun 2011 10:29:27 +0200</pubDate>
    </item>
    <item>
      <title>A Proposal for a Web Services Agreement Negotiation Protocol Framework</title>
      <link>http://opus4.kobv.de/opus4-bamberg/frontdoor/index/index/docId/278</link>
      <description>The WS-Agreement Standard as defined in the current proposal does not accommodate negotiation between service provider and requesters to yield an agreement. It is limited to simple offers and acceptances. However, negotiations between service providers and service consumers beyond the basic mechanism are required and are also part of the charter of the GRAAP working group. There are many mechanisms for negotiating agreements between parties for different purposes, having different sets of participants, different economic properties, different interactions patterns, and different information requirements to enter the interaction. Given the generality of the WS-Agreement scope, supporting a single negotiation mechanism would not satisfy the requirements of different application scenarios. Hence, the objective of this thesis is to devise a proposal to extend the WS-Agreement specification to facilitate the integration of arbitrary negotiation protocols into the WS-Agreement interaction. This includes facilities to enable a party to advertise the negotiation protocol it supports, the role that it can take in this protocol, expectations on other roles in the negotiation, and other meta-information that is necessary to start an interaction. This thesis analyzes the scope of negotiation protocols relevant for service level agreement establishment, derives a data structure for negotiation protocol meta-data, a protocol to exchange meta-data and initiate a negotiation protocol, and obtaining the result of the negotiation, the agreement. The new functionality extends the current WS-Agreement specification seamlessly. The thesis demonstrates the viability of the approach using scenarios of specific negotiation mechanisms.</description>
      <author>Sebastian Hudert</author>
      <category>masterthesis</category>
      <guid>http://opus4.kobv.de/opus4-bamberg/frontdoor/index/index/docId/278</guid>
      <pubDate>Mon, 30 May 2011 13:45:25 +0200</pubDate>
    </item>
    <item>
      <title>Analyzing the Interoperability of WS-Security and WS-ReliableMessaging Implementations</title>
      <link>http://opus4.kobv.de/opus4-bamberg/frontdoor/index/index/docId/249</link>
      <description>Since their invention as lightweight integration technology about a decade ago, Web Services have matured significantly. Today, major middleware solution vendors as well as industry communities like RosettaNet are propagating Web services even for exchanging business-critical data and implementing inter-organizational business processes. Core enablers for using Web services in this domain are stateful interactions using the Web Services Business Process Execution Language (WS-BPEL) as well as advanced communication features like security and reliability using the WS-Security and WS-ReliableMessaging standard specifications. However, advanced communication features come at the price of complexity which challenges interoperability across different Web services stack implementations. Interoperability, in turn, is a predominant requirement for an integration technology such as Web services, in particular if inter-organizational business processes are supposed to be implemented on top of that technology. This paper approaches the problem of testing the interoperability of the so-called WS-* standards, advanced Web services communication features that are typically defined as SOAP extensions and configured using WS-Policy. Being essential to business process integration, WS-Security and WS-ReliableMessaging are selected as representatives of this group and the two major Java-based Web services stack implementations Metro and Axis2 are tested for interoperability. We operationalize the notion of interoperability for testing WS-* standards, suppose an approach for deriving test cases from WS-* specifications as well as a method for performing the test cases, and we provide a comprehensive interoperability review of the two selected Web services stack implementations.</description>
      <author>Johannes Schwalb; Andreas Schönberger</author>
      <category>report</category>
      <guid>http://opus4.kobv.de/opus4-bamberg/frontdoor/index/index/docId/249</guid>
      <pubDate>Wed, 13 Oct 2010 15:51:09 +0200</pubDate>
    </item>
    <item>
      <title>Proaktives Problem Management durch Eventkorrelation - ein Best Practice Ansatz</title>
      <link>http://opus4.kobv.de/opus4-bamberg/frontdoor/index/index/docId/245</link>
      <description>Im Servicegeschäft werden Eventkorrelationssysteme verwendet, um bevorstehende Systemzustände vorherzusagen und damit Anlagenausfälle zu vermeiden. Aus strategischer Sicht kann dies zu höherer Anlagenverfügbarkeit und bessere Planbarkeit beitragen. Unternehmen, die von diesem Wettbewerbsvorteil profitieren wollen, begegnen dabei häufig zwei grundlegenden Problemen: die Komplexität im Service steigt mit der Anzahl der Korrelationen. Gleichzeitig geht die Kostentransparenz für den Gesamtprozess verloren. Die vorliegende Arbeit zeigt, warum diese beiden Probleme entstehen und wie sie weitgehend vermieden werden können.</description>
      <author>Werner Zirkel; Guido Wirtz</author>
      <category>report</category>
      <guid>http://opus4.kobv.de/opus4-bamberg/frontdoor/index/index/docId/245</guid>
      <pubDate>Mon, 20 Sep 2010 11:01:00 +0200</pubDate>
    </item>
    <item>
      <title>A Requirements Analysis of Business-To-Business Integration</title>
      <link>http://opus4.kobv.de/opus4-bamberg/frontdoor/index/index/docId/217</link>
      <description>Ever fiercer competition has forced enterprises not only to optimize their own operations but also to cooperate with their suppliers and customers along their supply chains. Thus, competition today usually takes place between supply chains and not between individual enterprises. Business-To-Business integration (B2Bi) is a major task of supply chain management (SCM), and although it already has been researched for years, B2Bi is still an area of active research with a plethora of research questions and according approaches. Hence, management of B2Bi projects necessitates the identification of relevant requirements which is a far from trivial task. This paper identifies a core set of B2Bi challenges and deduces a comprehensive set of B2Bi requirements that are particularly useful for tackling the challenges identified. The derivation of B2Bi requirements follows an inductive approach that is based on the analysis of integration standards, reference architectures and related literature. In order to operationalize the B2Bi requirements for further analysis and concrete B2Bi projects, the requirements are classified according to the abstraction layers of a B2Bi schema. Thus, this report not only offers a requirements check list for B2Bi projects but also helps in deciding when to address which requirements during the course of a B2Bi project.</description>
      <author>Andreas Schönberger; Christian Wilms; Guido Wirtz</author>
      <category>report</category>
      <guid>http://opus4.kobv.de/opus4-bamberg/frontdoor/index/index/docId/217</guid>
      <pubDate>Thu, 20 May 2010 13:32:46 +0200</pubDate>
    </item>
    <item>
      <title>Improving the Tor Hidden Service Protocol Aiming at Better Performances</title>
      <link>http://opus4.kobv.de/opus4-bamberg/frontdoor/index/index/docId/211</link>
      <description>Offering services anonymously on the Internet using so-called location-hidden services requires complex protocols with many different nodes involved. These properties result in performance problems, e.g. a simple website request taking tens of seconds. This work describes a setup to measure the performance of hidden services using the worldwide Tor network. It analyzes the results and proposes changes to the protocol to improve the performance without losing anonymity.</description>
      <author>Christian Wilms</author>
      <category>report</category>
      <guid>http://opus4.kobv.de/opus4-bamberg/frontdoor/index/index/docId/211</guid>
      <pubDate>Fri, 23 Apr 2010 14:42:30 +0200</pubDate>
    </item>
    <item>
      <title>Symbolic Object Code Analysis</title>
      <link>http://opus4.kobv.de/opus4-bamberg/frontdoor/index/index/docId/209</link>
      <description>Current software model checkers quickly reach their limit when being applied to verifying pointer safety properties in source code that includes function pointers and inlined assembly. This paper introduces an alternative technique for checking pointer safety violations, called Symbolic Object Code Analysis (SOCA), which is based on bounded symbolic execution, incorporates path-sensitive slicing, and employs the SMT solver Yices as its execution and verification engine. Extensive experimental results of a prototypic SOCA Verifier, using the Verisec suite and almost 10,000 Linux device driver functions as benchmarks, show that SOCA performs competitively to current source-code model checkers and that it also scales well when applied to real operating systems code and pointer safety issues. SOCA effectively explores semantic niches of software that current software verifiers do not reach.</description>
      <author>Jan Tobias Mühlberg; Gerald Lüttgen</author>
      <category>report</category>
      <guid>http://opus4.kobv.de/opus4-bamberg/frontdoor/index/index/docId/209</guid>
      <pubDate>Tue, 09 Mar 2010 11:42:05 +0100</pubDate>
    </item>
    <item>
      <title>A Process for Identifying Predictive Correlation Patterns in Service Management Systems</title>
      <link>http://opus4.kobv.de/opus4-bamberg/frontdoor/index/index/docId/206</link>
      <description>By using the remote functions of a modern IT service management system infrastructure, it is possible to analyze huge amounts of logfile data from complex technical equipment. This enables a service provider to predict failures of connected equipment before they happen. The problem most providers face in this context is finding a needle in a haystack - the obtained amount of data turns out to be too large to be analyzed manually. This report describes a process to find suitable predictive patterns in log files for the detection of upcoming critical situations. The identification process may serve as a hands-on guide. It describes how to connect statistical means, data mining algorithms and expert domain knowledge in the domain of service management. The process was developed in a research project which is currently being carried out within the Siemens Healthcare service organization. The project deals with two main aspects: First, the identification of predictive patterns in existing service data and second, the architecture of an autonomous agent which is able to correlate such patterns. This paper summarizes the results of the first project challenge. The identification process was tested successfully in a proof of concept for several Siemens Healthcare products.</description>
      <author>Werner Zirkel; Guido Wirtz</author>
      <category>report</category>
      <guid>http://opus4.kobv.de/opus4-bamberg/frontdoor/index/index/docId/206</guid>
      <pubDate>Thu, 25 Feb 2010 11:48:41 +0100</pubDate>
    </item>
    <item>
      <title>Proceedings of the KI 2009 Workshop on Complex Cognition</title>
      <link>http://opus4.kobv.de/opus4-bamberg/frontdoor/index/index/docId/189</link>
      <description>The KI ´09 workshop on Complex Cognition was a joint venture of the Cognition group of the Special Interest Group Artificial Intelligence of the German Computer Science Society (Gesellschaft für Informatik) and the German Cognitive Science Association. Dealing with complexity has become one of the great challenges for modern information societies. To reason and decide, plan and act in complex domains is no longer limited to highly specialized professionals in restricted areas such as medical diagnosis, controlling technical processes, or serious game playing. Complexity has reached everyday life and affects people in such mundane activities as buying a train ticket, investing money, or connecting a home desktop to the internet. Research in cognitive AI can contribute to supporting people navigating through the jungle of everyday reasoning, decision making, planning and acting by providing intelligent support technology. Lessons learned from expert systems research of the nineteen-eighties show that the aim should not be to provide for fully automated systems which can solve specialized tasks autonomously but instead to develop interactive assistant systems where user and system work together by taking advantage of the respective strengths of human and machine. To accomplish a smooth collaboration between humans and intelligent systems, basic research in cognition is a necessary precondition. Insights into cognitive structures and processes underlying successful human reasoning and planning can provide suggestions for algorithm design. Even more important, insights into restrictions and typical errors and misconceptions of the cognitive systems provide information about those parts of a complex task from which the human should be relieved. For successful human-computer interaction in complex domains it has, furthermore, to be decided which information should be presented when, in what way, to the user. We strongly believe that symbolic approaches of AI and psychological research of higher cognition are at the core of success for the endeavor to create intelligent assistant system for complex domains. While insight into the neurological processes of the brain and into the realization of basic processes of perception, attention and senso-motoric coordination are important for the basic understanding of the principles of human intelligence, these processes have a much too fine granularity for the design and realization of interactive systems which must communicate with the user on knowledge level. If human system users are not to be incapacitated by a system, system decisions must be transparent for the user and the system must be able to provide explanations for the reasons of its proposals and recommendations. Therefore, even when some of the underlying algorithms are based on statistical or neuronal approaches, the top-level of such systems must be symbolical and rule-based. The papers presented at this workshop on complex cognition give an inspiring and promising overview of current work in the field which can provide first building stones for our endeavor to create knowledge level intelligent assistant systems for complex domains. The topics cover modelling basic cognitive processes, interfacing subsymbolic and symbolic representations, dealing with continuous time, Bayesian identification of problem solving strategies, linguistically inspired methods for assessing complex cognitive processes and complex domains such as recognition of sketches, predicting changes in stocks, spatial information processing, and coping with critical situations.</description>
      <author/>
      <category>conferenceobject</category>
      <guid>http://opus4.kobv.de/opus4-bamberg/frontdoor/index/index/docId/189</guid>
      <pubDate>Fri, 23 Oct 2009 10:27:27 +0200</pubDate>
    </item>
    <item>
      <title>Proceedings of the ACM SIGPLAN Workshop on Approaches and Applications of Inductive Programming (AAIP 2009)</title>
      <link>http://opus4.kobv.de/opus4-bamberg/frontdoor/index/index/docId/183</link>
      <description>Inductive programming is concerned with the automated construction of declarative, often functional, recursive programs from incomplete specifications such as input/output examples. The inferred program must be correct with respect to the provided examples in a generalising sense: it should be neither equivalent to them, nor inconsistent. Inductive programming algorithms are guided explicitly or implicitly by a language bias (the class of programs that can be induced) and a search bias (determining which generalised program is constructed first). Induction strategies are either generate-and-test or example-driven. In generate-and-test approaches, hypotheses about candidate programs are generated independently from the given specifications. Program candidates are tested against the given specification and one or more of the best evaluated candidates are developed further. In analytical approaches, candidate programs are constructed in an example-driven way. While generate-and-test approaches can -- in principle -- construct any kind of program, analytical approaches have a more limited scope. On the other hand, efficiency of induction is much higher in analytical approaches. Inductive programming is still mainly a topic of basic research, exploring how the intellectual ability of humans to infer generalised recursive procedures from incomplete evidence can be captured in the form of synthesis methods. Intended applications are mainly in the domain of programming assistance -- either to relieve professional programmers from routine tasks or to enable non-programmers to some limited form of end-user programming. Furthermore, in the future, inductive programming techniques might be applied to further areas such as supporting the inference of lemmata in theorem proving or learning grammar rules. Inductive automated program construction has been originally addressed by researchers in artificial intelligence and machine learning. During the last years, some work on exploiting induction techniques has been started also in the functional programming community. Therefore, the third workshop on |Approaches and Applications of Inductive Programming| took place for the first time in conjunction with the ACM SIGPLAN International Conference on Functional Programming (ICFP 2009). The first and second workshop were associated with the International Conference on Machine Learning (ICML 2005) and the European Conference on Machine Learning (ECML 2007). AAIP´09 aimed to bring together researchers from the functional programming and the artificial intelligence communities, working in the field of inductive functional programming, and advance fruitful interactions between these communities with respect to programming techniques for inductive programming algorithms, the identification of challenge problems and potential applications. For everybody interested in inductive programming we recommend to visit the website: www.inductive-programming.org.</description>
      <author/>
      <category>conferenceobject</category>
      <guid>http://opus4.kobv.de/opus4-bamberg/frontdoor/index/index/docId/183</guid>
      <pubDate>Wed, 23 Sep 2009 10:32:56 +0200</pubDate>
    </item>
    <item>
      <title>QoS-Enabled B2B Integration</title>
      <link>http://opus4.kobv.de/opus4-bamberg/frontdoor/index/index/docId/182</link>
      <description>Business-To-Business Integration (B2Bi) is a key mechanism for enterprises to gain competitive advantage. However, developing B2Bi applications is far from trivial. Inter alia, agreement among integration partners about the business documents and the control flow of business document exchanges as well as applying suitable communication technologies for overcoming heterogeneous IT landscapes are major challenges. At the same time, choreography languages such as ebXML BPSS (ebBP), orchestration languages such as WS-BPEL and Web Services are promising to provide the foundations for seamless interactions among business partners. Automatically translating choreography agreements of integration partners into partner-specific orchestrations is an obvious idea for ensuring conformance of orchestration models to choreography models. Moreover, the application of such model-driven development methods facilitates productivity and cost-effectiveness whereas applying a service oriented architecture (SOA) based on WS-BPEL and Web Services leverages standardization and decoupling. By now, the realization of QoS attributes has not yet received the necessary attention that makes such approaches suitable for B2Bi. In this report, we describe a proof-of-concept implementation of the translation of ebBP choreographies into WS-BPEL orchestrations that respects B2Bi-relevant QoS attributes.</description>
      <author>Thomas Benker; Stefan Fritzemeier; Matthias Geiger; Simon Harrer; Tristan Kessner; Johannes Schwalb; Andreas Schoenberger; Guido Wirtz</author>
      <category>report</category>
      <guid>http://opus4.kobv.de/opus4-bamberg/frontdoor/index/index/docId/182</guid>
      <pubDate>Mon, 14 Sep 2009 11:59:12 +0200</pubDate>
    </item>
    <item>
      <title>A Service Description Framework for Service Ecosystems</title>
      <link>http://opus4.kobv.de/opus4-bamberg/frontdoor/index/index/docId/158</link>
      <description>Recently, service orientation has strongly influenced the way enterprise applications are built. Service ecosystems, which provide means to trade services between companies like goods, are an evaluation of service orientation. To allow service ordering, discovering, selection, and consumption, a common way to describe services is a necessity. This paper discusses existing approaches to describe certain service aspects. Finally, a Service Description Framework for service ecosystems is proposed and exemplified.</description>
      <author>Gregor Scheithauer; Matthias Winkler</author>
      <category>report</category>
      <guid>http://opus4.kobv.de/opus4-bamberg/frontdoor/index/index/docId/158</guid>
      <pubDate>Wed, 21 Jan 2009 15:47:41 +0100</pubDate>
    </item>
    <item>
      <title>Applying Business Process Management Systems - a Case Study </title>
      <link>http://opus4.kobv.de/opus4-bamberg/frontdoor/index/index/docId/134</link>
      <description>Business Process Management Systems (BPMS) aim to support the Business Process Management paradigm and to ease legacy application integration. Often, they rely on Service-oriented Architecture (SoA). However, do such systems really meet real-world requirements? This paper introduces and discusses a set of criteria which are important for BPMS and applies these criteria in comparing tools from three important vendors, namely IDS Scheer, Oracle and Intalio based on a case study.</description>
      <author>Gregor Scheithauer; Guido Wirtz</author>
      <category>report</category>
      <guid>http://opus4.kobv.de/opus4-bamberg/frontdoor/index/index/docId/134</guid>
      <pubDate>Tue, 15 Jul 2008 16:08:41 +0200</pubDate>
    </item>
    <item>
      <title>Extended Abstracts of the Second Privacy Enhancing Technologies Convention (PET-CON 2008.1)</title>
      <link>http://opus4.kobv.de/opus4-bamberg/frontdoor/index/index/docId/122</link>
      <description>PET-CON, the Privacy Enhancing Technologies Convention, is a forum for researchers, students, developers, and other interested people to discuss novel research, current developments and techniques in the area of Privacy Enhancing Technologies. PET-CON was first conceived in June 2007 at the 7th International PET Symposium in Ottawa, Canada. The idea was to set up a bi-annual convention in or nearby Germany to be able to meet more often than only once a year at some major conference.</description>
      <author>Dominik Herrmann; Karsten Loesing; Sebastian Pape; Johannes Renner; Rolf Wendolsky; Benedikt Westermann</author>
      <category>conferenceobject</category>
      <guid>http://opus4.kobv.de/opus4-bamberg/frontdoor/index/index/docId/122</guid>
      <pubDate>Fri, 08 Feb 2008 14:53:35 +0100</pubDate>
    </item>
    <item>
      <title>Open Chord version 1.0.4 User's Manual</title>
      <link>http://opus4.kobv.de/opus4-bamberg/frontdoor/index/index/docId/113</link>
      <description>In recent years peer-to-peer networks have developed from unstructured to structured overlay networks. Structured peer-to-peer overlay networks facilitate a bounded number of messages in the number of peers for querying and publishing content opposed to unstructured networks, which usually flood the network with messages. To prevent the messages from overflooding the network they have a bounded life time, which may cause that some published content will be lost. Structured peer-to-peer networks guarantee that all published content can be found. One well known structured overlay network is the chord distributed hash table. An implementation of chord is only available in C, but not in Java, which is used widely and often in computer science education. This manual describes an open source implementation of chord in Java - called Open Chord - and how it can be used in Java-based applications. It provides a console-based experimentation environment to explore the functionality of chord, as well.</description>
      <author>Sven Kaffille; Karsten Loesing</author>
      <category>report</category>
      <guid>http://opus4.kobv.de/opus4-bamberg/frontdoor/index/index/docId/113</guid>
      <pubDate>Tue, 13 Nov 2007 08:20:13 +0100</pubDate>
    </item>
    <item>
      <title>Decentralized Reputation Management for Cooperating Software Agents in Open Multi-Agent Systems</title>
      <link>http://opus4.kobv.de/opus4-bamberg/frontdoor/index/index/docId/87</link>
      <description>Multi-Agent Systems (MAS) promise a new advance in distributed computing. In MAS autonomous software agents flexibly cooperate, coordinate, and compete to provide the desired function(s) of such a system. If some components of a MAS fail or do not provide the desired functionality, the system is expected to autonomously deal with these situations. It is desirable to reduce occurrences of such situations by selecting trustworthy cooperation partners before cooperating with them. This becomes even more desirable and important in an open MAS where arbitrary heterogeneous software agents, deployed by different parties, participate in the MAS, as it becomes more likely that these agents fail or try to exploit the MAS for their own purposes without reciprocation. In order to monitor agent behavior and enable selection of trustworthy cooperation partners, trust or reputation management services can be applied. As there is no central control in an open MAS and it is completely distributed these services themselves have to be distributed. This paper proposes a fully distributed reputation management service for open MAS based on peer-to-peer technology (especially distributed hash tables). A Java-based implementation of that service, which is intended as a plug-in for multi-agent platforms, is also described.</description>
      <author>Marco Fischer; Andreas Grünert; Sebastian Hudert; Stefan König; Kira Lenskaya; Gregor Scheithauer; Sven Kaffille; Guido Wirtz</author>
      <category>report</category>
      <guid>http://opus4.kobv.de/opus4-bamberg/frontdoor/index/index/docId/87</guid>
      <pubDate>Fri, 18 Aug 2006 13:53:34 +0200</pubDate>
    </item>
    <item>
      <title>Concealing Presence Information in Instant Messaging Systems</title>
      <link>http://opus4.kobv.de/opus4-bamberg/frontdoor/index/index/docId/77</link>
      <description>Information about online presence allows participants of instant messaging (IM) systems to determine whether their prospective communication partners will be able to answer their requests in a timely manner, or not. That is why presence information, combined with the ability to send instant messages, makes IM more personal and closer than other forms of communication such as e-mail. On the other hand, revelation of presence constitutes a potential of misuse by untrustworthy entities. A possible risk is the generation of online logs disclosing user habits. This makes presence information a resource worth protecting. We argue, however, that current IM systems do not take reasonable precautions to protect presence information. We implemented an IM system designed to be robust against attacks to disclose a user’s presence. In contrast to existing systems, it stores presence information in a registry in a way that is only detectable and applicable for intended users and not comprehensible even for the registry itself. We use a distributed hash table (DHT) as registry and apply an anonymous communication network to protect the physical addresses of both senders and receivers of messages.</description>
      <author>Markus Dorsch; Martin Grote; Knut Hildebrandt; Maximilian Röglinger; Matthias Sehr; Christian Wilms; Karsten Loesing; Guido Wirtz</author>
      <category>report</category>
      <guid>http://opus4.kobv.de/opus4-bamberg/frontdoor/index/index/docId/77</guid>
      <pubDate>Tue, 11 Apr 2006 07:54:50 +0200</pubDate>
    </item>
    <item>
      <title>Modelling and Validating Business Collaborations: A Case Study on RosettaNet</title>
      <link>http://opus4.kobv.de/opus4-bamberg/frontdoor/index/index/docId/73</link>
      <description>The way business processes are organised heavily influences the flexibility and the expenses of enterprises. The capability to address changing market needs in a timely manner and to provide appropriate pricing is indispensable in a world of internationalisation and growing competition. Optimising processes that cross enterprise boundaries potentially is a key success factor in achieving this goal but it requires the information systems of the participating enterprises to be consistently integrated. This gives rise to some challenging tasks. The personnel involved in building up business collaborations comes from different enterprises with different business vocabulary and background which requires extensive communication support. The lack of central technical infrastructure, typically prohibited by business politics, often calls for a distributed and computer-aided collaboration structure, so that the resulting complexity must be handled somehow. Nevertheless robustness is an important factor in building business collaborations as these may exchange goods of considerable value. This technical report proposes the use of a two step modelling approach that separates business logic, modelled in the so-called centralised perspective (CP), from its distributed implementation, modelled in the so-called distributed perspective (DP). The separation of these perspectives enables business people to concentrate on business issues and to solve communication problems in the CP whereas technical staff can concentrate on distribution issues. The use of stringent modelling rules is advised in order to provide the basis for formal analysis techniques as one means to achieve robustness. Considering the choreography of RosettaNet Partner Interface Processes (PIPs) as the subject of my analysis, UML activity diagrams for modelling the CP and WSBPEL for modelling the DP are described as enabling techniques for implementing the proposed two step modelling approach. Further, model checking is applied to validate the CP and DP models in order to detect errors in early design phases. As the adequacy of model checking tools highly depends on the detailed modelling techniques as well as the properties to be checked, a major part of our discussion covers relevant properties and requirements for a model checker.</description>
      <author>Andreas Schönberger</author>
      <category>report</category>
      <guid>http://opus4.kobv.de/opus4-bamberg/frontdoor/index/index/docId/73</guid>
      <pubDate>Thu, 30 Mar 2006 12:02:10 +0200</pubDate>
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