TY - JOUR A1 - Sarsakov, Vladimir A1 - Schaub, Torsten H. A1 - Tompits, Hans A1 - Woltran, Stefan T1 - A compiler for nested logic programming Y1 - 2004 SN - 3-540- 20721-x ER - TY - JOUR A1 - Linke, Thomas A1 - Tompits, Hans A1 - Woltran, Stefan T1 - On Acyclic and head-cycle free nested logic programs Y1 - 2004 SN - 3-540-22671-01 ER - TY - JOUR A1 - Linke, Thomas A1 - Tompits, Hans A1 - Woltran, Stefan T1 - On acyclic and head-cycle free nested logic programs Y1 - 2004 ER - TY - JOUR A1 - Delgrande, James Patrick A1 - Schaub, Torsten H. A1 - Tompits, Hans A1 - Woltran, Stefan T1 - On Computing belief change operations using quantifield boolean formulas N2 - In this paper, we show how an approach to belief revision and belief contraction can be axiomatized by means of quantified Boolean formulas. Specifically, we consider the approach of belief change scenarios, a general framework that has been introduced for expressing different forms of belief change. The essential idea is that for a belief change scenario (K, R, C), the set of formulas K, representing the knowledge base, is modified so that the sets of formulas R and C are respectively true in, and consistent with the result. By restricting the form of a belief change scenario, one obtains specific belief change operators including belief revision, contraction, update, and merging. For both the general approach and for specific operators, we give a quantified Boolean formula such that satisfying truth assignments to the free variables correspond to belief change extensions in the original approach. Hence, we reduce the problem of determining the results of a belief change operation to that of satisfiability. This approach has several benefits. First, it furnishes an axiomatic specification of belief change with respect to belief change scenarios. This then leads to further insight into the belief change framework. Second, this axiomatization allows us to identify strict complexity bounds for the considered reasoning tasks. Third, we have implemented these different forms of belief change by means of existing solvers for quantified Boolean formulas. As well, it appears that this approach may be straightforwardly applied to other specific approaches to belief change Y1 - 2004 SN - 0955-792X ER - TY - BOOK A1 - Saposhnikov, V. V. A1 - Saposhnikov, Vl. V. A1 - Morozov, Alexei A1 - Gössel, Michael T1 - Necessary and Sufficient Conditions for the Existence of Self-Checking Circuits ba Use of Complementary Circuits T3 - Preprint / Universität Potsdam, Institut für Informatik Y1 - 2004 SN - 0946-7580 VL - 2004, 1 PB - Univ. CY - Potsdam ER - TY - JOUR A1 - Konczak, Kathrin A1 - Linke, Thomas A1 - Schaub, Torsten H. T1 - Graphs and cologings for answer set programming : adridged report Y1 - 2004 SN - 3-540- 20721-x ER - TY - JOUR A1 - Boesel, Andreas A1 - Linke, Thomas A1 - Schaub, Torsten H. T1 - Profiling answer set programming : the visualization component of the noMoRe System Y1 - 2004 SN - 3-540-23242-7 ER - TY - BOOK A1 - Bensch, Suna A1 - Boldt, Oliver A1 - Bordihn, Henning A1 - Jürgensen, Helmut T1 - Workshop "Formale Methoden der Linguistik" und "14. Theorietag Automaten und Formale Sprachen" T3 - Preprint / Universität Potsdam, Institut für Informatik Y1 - 2004 SN - 0946-7580 VL - 2004, 2 PB - Univ. CY - Potsdam ER - TY - BOOK A1 - Nazajkinskij, Vladimir E. A1 - Savin, Anton A1 - Schulze, Bert-Wolfgang A1 - Sternin, Boris T1 - Elliptic theory on manifolds with edges T3 - Preprint / Universität Potsdam, Institut für Mathematik, Arbeitsgruppe Partiell Y1 - 2004 SN - 1437-739X PB - Univ. CY - Potsdam ER - TY - BOOK A1 - Liu, Xiaochun A1 - Schulze, Bert-Wolfgang T1 - Boundary value problems in edge representation T3 - Preprint / Universität Potsdam, Institut für Mathematik, Arbeitsgruppe Partiell Y1 - 2004 SN - 1437-739X PB - Univ. CY - Potsdam ER - TY - BOOK A1 - Nazajkinskij, Vladimir E. A1 - Savin, Anton A1 - Schulze, Bert-Wolfgang A1 - Sternin, Boris T1 - On the homotopy classification of elliptic operators on manifolds with edges T3 - Preprint / Universität Potsdam, Institut für Mathematik, Arbeitsgruppe Partiell Y1 - 2004 SN - 1437-739X PB - Univ. CY - Potsdam ER - TY - BOOK A1 - Egorov, Yu. A1 - Kondratiev, V. A. A1 - Schulze, Bert-Wolfgang T1 - On the completeness of root functions of elliptic boundary problems in a domain with conical points on the boundary T3 - Preprint / Universität Potsdam, Institut für Mathematik, Arbeitsgruppe Partiell Y1 - 2004 SN - 1437-739X PB - Univ. CY - Potsdam ER - TY - BOOK A1 - Kytmanov, Alexander M. A1 - Myslivets, Simona A1 - Tarkhanov, Nikolai Nikolaevich T1 - Zeta-function of a nonlinear system T3 - Preprint / Universität Potsdam, Institut für Mathematik, Arbeitsgruppe Partiell Y1 - 2004 SN - 1437-739X PB - Univ. CY - Potsdam ER - TY - BOOK A1 - Tarkhanov, Nikolai Nikolaevich T1 - Harmonic integrals on domains with edges T3 - Preprint / Universität Potsdam, Institut für Mathematik, Arbeitsgruppe Partiell Y1 - 2004 SN - 1437-739X PB - Univ. CY - Potsdam ER - TY - BOOK A1 - Kytmanov, Alexander M. A1 - Myslivets, Simona A1 - Tarkhanov, Nikolai Nikolaevich T1 - Power sums of roots of a nonlinear system T3 - Preprint / Universität Potsdam, Institut für Mathematik, Arbeitsgruppe Partiell Y1 - 2004 SN - 1437-739X PB - Univ. CY - Potsdam ER - TY - BOOK ED - Rebensburg, Klaus T1 - Grundfragen Multimedialen Lehrens und Lernens : 2. Workshop GML2 2004 N2 - Tagungsband vom 2. Workshop GML² 2005 Dem Lernen und Lehren mit Neuen Medien werden in Zeiten der Informationsgesellschaft oft sagenhafte Eigenschaften zugeschrieben: es sei anschaulicher, attraktiver, motivierender, effizienter, kostengünstiger, gehe besser auf den Lernenden ein, steigere den Lernerfolg, orientiere sich mehr an den kognitiven Strukturen von Lernenden etc.. Damit wenigstens einige der genannten Vorteile wirksam werden, sind geeignete didaktische und methodische Modelle und Konzepte unverzichtbar. Hinzu kommen detaillierte Kenntnisse in der Gestaltung von Lernoberflächen, der technischen Realisierung von Lerninhalten, dem Aufbau lernförderlicher Strukturen und Betreuungskonzepte und dem Betrieb von teilweise virtuellen Universitäten. Inwieweit gesteckte Ziele erreicht wurden, ist anhand von Evaluationsmaßnahmen zu ermitteln. Sämtliche Aspekte müssen bereits in die Planung entsprechender Angebote einbezogen werden. Y1 - 2004 SN - 3-8334-1573-8 PB - Books on Demand CY - Norderstedt ER - TY - JOUR A1 - Borchert, P. A1 - Anger, Christian A1 - Schaub, Torsten H. A1 - Truszczynski, M. T1 - Towards systematic benchmarking in answer set programming : the dagstuhl initiative Y1 - 2004 SN - 3-540- 20721-x ER - TY - THES A1 - Grunske, Lars T1 - Strukturorientierte Optimierung der Qualitätseigenschaften von softwareintensiven technischen Systemen im Architekturentwurf Y1 - 2004 ER - TY - BOOK A1 - Tepoyan, Liparit T1 - The Neumann problem for a degenerate operator equation T3 - Preprint / Universität Potsdam, Institut für Mathematik, Arbeitsgruppe Partiell Y1 - 2004 SN - 1437-739X PB - Univ. CY - Potsdam ER - TY - BOOK A1 - Harutjunjan, Gohar A1 - Schulze, Bert-Wolfgang T1 - Boundary problems with meromorphic symbols in cylindrical domains T3 - Preprint / Universität Potsdam, Institut für Mathematik, Arbeitsgruppe Partiell Y1 - 2004 SN - 1437-739X PB - Univ. CY - Potsdam ER - TY - JOUR A1 - Weske, Mathias A1 - van der Aalst, Wil M. P. A1 - Verbeek, H. M. W. T1 - Advances in business process management Y1 - 2004 SN - 0169-023X ER - TY - JOUR A1 - Delgrande, James Patrick A1 - Schaub, Torsten H. T1 - Two approaches to merging knowledge bases Y1 - 2004 SN - 3-540-23242-7 ER - TY - JOUR A1 - Delgrande, James Patrick A1 - Schaub, Torsten H. A1 - Tompits, Hans T1 - Domain-specific preference for causal reasoning and planning Y1 - 2004 SN - 1-577-35201-7 ER - TY - BOOK A1 - Niu, Pengcheng A1 - Han, Yazhou T1 - Hardy-Sobolev type inequalities on the Heisenberg Group T3 - Preprint / Universität Potsdam, Institut für Mathematik, Arbeitsgruppe Partiell Y1 - 2004 SN - 1437-739X PB - Univ. CY - Potsdam ER - TY - BOOK A1 - Gil, J. B. A1 - Krainer, Thomas A1 - Mendoza, A. T1 - Geometry and Spectra of closed extensions of elliptic cone operators T3 - Preprint / Universität Potsdam, Institut für Mathematik, Arbeitsgruppe Partiell Y1 - 2004 SN - 1437-739X PB - Univ. CY - Potsdam ER - TY - BOOK A1 - Gil, J. B. A1 - Krainer, Thomas A1 - Mendoza, A. T1 - Resolvents of elliptic cone operators T3 - Preprint / Universität Potsdam, Institut für Mathematik, Arbeitsgruppe Partiell Y1 - 2004 SN - 1437-739X PB - Univ. CY - Potsdam ER - TY - JOUR A1 - Flöter, André A1 - Selbig, Joachim A1 - Schaub, Torsten H. T1 - Finding metabolic pathways in decision forests Y1 - 2004 SN - 3-540-23221-4 ER - TY - JOUR A1 - Delgrande, James Patrick A1 - Schaub, Torsten H. T1 - Consistency-based approaches to merging knowledge based : preliminary report Y1 - 2004 UR - http://www.pims.math.ca/science/2004/NMR/papers/paper17.pdf SN - 92-990021-0-X ER - TY - JOUR A1 - Nicolelis, Miguel Angelo L. A1 - Birbaumer, Niels A1 - Muller, K. R. T1 - Untitled Y1 - 2004 SN - 0018-9294 ER - TY - BOOK A1 - Kuhrmann, Marco T1 - Überlegungen zum Dienst als Softwarebauelement T3 - Preprint / Universität Potsdam, Institut für Informatik Y1 - 2004 SN - 0946-7580 VL - 2004, 3 PB - Univ. CY - Potsdam ER - TY - JOUR A1 - Bordihn, Henning T1 - Context-freeness of the power of context-free languages is undecidable N2 - The power of a language L is the set of all powers of the words in L. In this paper, the following decision problem is investigated. Given a context-free language L, is the power of L context-free? We show that this problem is decidable for languages over unary alphabets, but it is undecidable whenever languages over alphabets with at least two letters are considered. (C) 2003 Elsevier B.V. All rights reserved Y1 - 2004 SN - 0304-3975 ER - TY - JOUR A1 - Dornhege, Guido A1 - Blankertz, Benjamin A1 - Curio, Gabriel A1 - Müller, Klaus-Robert T1 - Boosting bit rates in noninvasive EEG single-trial classifications by feature combination and multiclass paradigms N2 - Noninvasive electroencephalogram (EEG) recordings provide for easy and safe access to human neocortical processes which can be exploited for a brain-computer interface (BCI). At present, however, the use of BCIs is severely limited by low bit-transfer rates. We systematically analyze and develop two recent concepts, both capable of enhancing the information gain from multichannel scalp EEG recordings: 1) the combination of classifiers, each specifically tailored for different physiological phenomena, e.g., slow cortical potential shifts, such as the premovement Bereitschaftspotential or differences in spatio-spectral distributions of brain activity (i.e., focal event-related desynchronizations) and 2) behavioral paradigms inducing the subjects to generate one out of several brain states (multiclass approach) which all bare a distinctive spatio-temporal signature well discriminable in the standard scalp EEG. We derive information-theoretic predictions and demonstrate their relevance in experimental data. We will show that a suitably arranged interaction between these concepts can significantly boost BCI performances Y1 - 2004 ER - TY - JOUR A1 - Blankertz, Benjamin A1 - Müller, Klaus-Robert A1 - Curio, Gabriel A1 - Vaughan, Theresa M. A1 - Schalk, Gerwin A1 - Wolpaw, Jonathan R. A1 - Schlogl, Alois A1 - Neuper, Christa A1 - Pfurtscheller, Gert A1 - Hinterberger, Thilo A1 - Schroder, Michael A1 - Birbaumer, Niels T1 - The BCI competition 2003 : Progress and perspectives in detection and discrimination of EEG single trials N2 - Interest in developing a new method of man-to-machine communication-a brain-computer interface (BCI)-has grown steadily over the past few decades. BCIs create a new communication channel between the brain and an output device by bypassing conventional motor output pathways of nerves and muscles. These systems use signals recorded from the scalp, the surface of the cortex, or from inside the brain to enable users to control a variety of applications including simple word-processing software and orthotics. BCI technology could therefore provide a new communication and control option for individuals who cannot otherwise express their wishes to the outside world. Signal processing and classification methods are essential tools in the development of improved BCI technology. We organized the BCI Competition 2003 to evaluate the current state of the art of these tools. Four laboratories well versed in EEG-based BCI research provided six data sets in a documented format. We made these data sets (i.e., labeled training sets and unlabeled test sets) and their descriptions available on the Internet. The goal in the competition was to maximize the performance measure for the test labels. Researchers worldwide tested their algorithms and competed for the best classification results. This paper describes the six data sets and the results and function of the most successful algorithms Y1 - 2004 SN - 0018-9294 ER - TY - JOUR A1 - Flöter, André A1 - Nicolas, Jacques A1 - Schaub, Torsten H. A1 - Selbig, Joachim T1 - Threshold extraction in metabolite concentration data N2 - Motivation: Continued development of analytical techniques based on gas chromatography and mass spectrometry now facilitates the generation of larger sets of metabolite concentration data. An important step towards the understanding of metabolite dynamics is the recognition of stable states where metabolite concentrations exhibit a simple behaviour. Such states can be characterized through the identification of significant thresholds in the concentrations. But general techniques for finding discretization thresholds in continuous data prove to be practically insufficient for detecting states due to the weak conditional dependences in concentration data. Results: We introduce a method of recognizing states in the framework of decision tree induction. It is based upon a global analysis of decision forests where stability and quality are evaluated. It leads to the detection of thresholds that are both comprehensible and robust. Applied to metabolite concentration data, this method has led to the discovery of hidden states in the corresponding variables. Some of these reflect known properties of the biological experiments, and others point to putative new states Y1 - 2004 ER - TY - JOUR A1 - Harmeling, Stefan A1 - Meinecke, Frank C. A1 - Müller, Klaus-Robert T1 - Injecting noise for analysing the stability of ICA components N2 - Usually, noise is considered to be destructive. We present a new method that constructively injects noise to assess the reliability and the grouping structure of empirical ICA component estimates. Our method can be viewed as a Monte-Carlo-style approximation of the curvature of some performance measure at the solution. Simulations show that the true root-mean-squared angle distances between the real sources and the source estimates can be approximated well by our method. In a toy experiment, we see that we are also able to reveal the underlying grouping structure of the extracted ICA components. Furthermore, an experiment with fetal ECG data demonstrates that our approach is useful for exploratory data analysis of real-world data. (C) 2003 Elsevier B.V. All rights reserved Y1 - 2004 SN - 0165-1684 ER - TY - JOUR A1 - Delgrande, James Patrick A1 - Schaub, Torsten H. A1 - Tompits, Hans A1 - Wang, Kewen T1 - A classification and survey of preference handling approchaches in nonmonotonic reasoning N2 - In recent years, there has been a large amount of disparate work concerning the representation and reasoning with qualitative preferential information by means of approaches to nonmonotonic reasoning. Given the variety of underlying systems, assumptions, motivations, and intuitions, it is difficult to compare or relate one approach with another. Here, we present an overview and classification for approaches to dealing with preference. A set of criteria for classifying approaches is given, followed by a set of desiderata that an approach might be expected to satisfy. A comprehensive set of approaches is subsequently given and classified with respect to these sets of underlying principles Y1 - 2004 SN - 0824-7935 ER - TY - JOUR A1 - Delgrande, James Patrick A1 - Schaub, Torsten H. T1 - Reasoning with sets of preferences in default logic N2 - We present a general approach for representing and reasoning with sets of defaults in default logic, focusing on reasoning about preferences among sets of defaults. First, we consider how to control the application of a set of defaults so that either all apply (if possible) or none do (if not). From this, an approach to dealing with preferences among sets of default rules is developed. We begin with an ordered default theory, consisting of a standard default theory, but with possible preferences on sets of rules. This theory is transformed into a second, standard default theory wherein the preferences are respected. The approach differs from other work, in that we obtain standard default theories and do not rely on prioritized versions of default logic. In practical terms this means we can immediately use existing default logic theorem provers for an implementation. Also, we directly generate just those extensions containing the most preferred applied rules; in contrast, most previous approaches generate all extensions, then select the most preferred. In a major application of the approach, we show how semimonotonic default theories can be encoded so that reasoning can be carried out at the object level. With this, we can reason about default extensions from within the framework of a standard default logic. Hence one can encode notions such as skeptical and credulous conclusions, and can reason about such conclusions within a single extension Y1 - 2004 SN - 0824-7935 ER - TY - JOUR A1 - Goessel, Michael A1 - Chakrabarty, Krishnendu A1 - Ocheretnij, V. A1 - Leininger, Andreas T1 - A signature analysis technique for the identification of failing vectors with application to Scan-BIST N2 - We present a new technique for uniquely identifying a single failing vector in an interval of test vectors. This technique is applicable to combinational circuits and for scan-BIST in sequential circuits with multiple scan chains. The proposed method relies on the linearity properties of the MISR and on the use of two test sequences, which are both applied to the circuit under test. The second test sequence is derived from the first in a straightforward manner and the same test pattern source is used for both test sequences. If an interval contains only a single failing vector, the algebraic analysis is guaranteed to identify it. We also show analytically that if an interval contains two failing vectors, the probability that this case is interpreted as one failing vector is very low. We present experimental results for the ISCAS benchmark circuits to demonstrate the use of the proposed method for identifying failing test vectors Y1 - 2004 SN - 0923-8174 ER - TY - JOUR A1 - Müller, Klaus-Robert A1 - Vigario, R. A1 - Meinecke, Frank C. A1 - Ziehe, Andreas T1 - Blind source separation techniques for decomposing event-related brain signals N2 - Recently blind source separation (BSS) methods have been highly successful when applied to biomedical data. This paper reviews the concept of BSS and demonstrates its usefulness in the context of event-related MEG measurements. In a first experiment we apply BSS to artifact identification of raw MEG data and discuss how the quality of the resulting independent component projections can be evaluated. The second part of our study considers averaged data of event-related magnetic fields. Here, it is particularly important to monitor and thus avoid possible overfitting due to limited sample size. A stability assessment of the BSS decomposition allows to solve this task and an additional grouping of the BSS components reveals interesting structure, that could ultimately be used for gaining a better physiological modeling of the data Y1 - 2004 SN - 0218-1274 ER - TY - JOUR A1 - Sugiyama, Masashi A1 - Kawanabe, Motoaki A1 - Müller, Klaus-Robert T1 - Trading variance reduction with unbiasedness : the regularized subspace information criterion for robust model selection in kernel regression N2 - A well-known result by Stein (1956) shows that in particular situations, biased estimators can yield better parameter estimates than their generally preferred unbiased counterparts. This letter follows the same spirit, as we will stabilize the unbiased generalization error estimates by regularization and finally obtain more robust model selection criteria for learning. We trade a small bias against a larger variance reduction, which has the beneficial effect of being more precise on a single training set. We focus on the subspace information criterion (SIC), which is an unbiased estimator of the expected generalization error measured by the reproducing kernel Hilbert space norm. SIC can be applied to the kernel regression, and it was shown in earlier experiments that a small regularization of SIC has a stabilization effect. However, it remained open how to appropriately determine the degree of regularization in SIC. In this article, we derive an unbiased estimator of the expected squared error, between SIC and the expected generalization error and propose determining the degree of regularization of SIC such that the estimator of the expected squared error is minimized. Computer simulations with artificial and real data sets illustrate that the proposed method works effectively for improving the precision of SIC, especially in the high-noise-level cases. We furthermore compare the proposed method to the original SIC, the cross-validation, and an empirical Bayesian method in ridge parameter selection, with good results Y1 - 2004 SN - 0899-7667 ER - TY - JOUR A1 - Ziehe, Andreas A1 - Kawanabe, Motoaki A1 - Harmeling, Stefan T1 - Blind separation of post-nonlinear mixtures using linearizing transformations and temporal decorrelation N2 - We propose two methods that reduce the post-nonlinear blind source separation problem (PNL-BSS) to a linear BSS problem. The first method is based on the concept of maximal correlation: we apply the alternating conditional expectation (ACE) algorithm-a powerful technique from nonparametric statistics-to approximately invert the componentwise nonlinear functions. The second method is a Gaussianizing transformation, which is motivated by the fact that linearly mixed signals before nonlinear transformation are approximately Gaussian distributed. This heuristic, but simple and efficient procedure works as good as the ACE method. Using the framework provided by ACE, convergence can be proven. The optimal transformations obtained by ACE coincide with the sought-after inverse functions of the nonlinearitics. After equalizing the nonlinearities, temporal decorrelation separation (TDSEP) allows us to recover the source signals. Numerical simulations testing "ACE-TD" and "Gauss-TD" on realistic examples are performed with excellent results Y1 - 2004 SN - 1532-4435 ER - TY - THES A1 - Harmeling, Stefan T1 - Independent component analysis and beyond N2 - 'Independent component analysis' (ICA) ist ein Werkzeug der statistischen Datenanalyse und Signalverarbeitung, welches multivariate Signale in ihre Quellkomponenten zerlegen kann. Obwohl das klassische ICA Modell sehr nützlich ist, gibt es viele Anwendungen, die Erweiterungen von ICA erfordern. In dieser Dissertation präsentieren wir neue Verfahren, die die Funktionalität von ICA erweitern: (1) Zuverlässigkeitsanalyse und Gruppierung von unabhängigen Komponenten durch Hinzufügen von Rauschen, (2) robuste und überbestimmte ('over-complete') ICA durch Ausreissererkennung, und (3) nichtlineare ICA mit Kernmethoden. N2 - Independent component analysis (ICA) is a tool for statistical data analysis and signal processing that is able to decompose multivariate signals into their underlying source components. Although the classical ICA model is highly useful, there are many real-world applications that require powerful extensions of ICA. This thesis presents new methods that extend the functionality of ICA: (1) reliability and grouping of independent components with noise injection, (2) robust and overcomplete ICA with inlier detection, and (3) nonlinear ICA with kernel methods. T2 - Independent component analysis and beyond KW - ICA KW - Zuverlässigkeitsanalyse KW - robuste ICA KW - überbestimmte ICA KW - Ausreissererkennung KW - nichtlineare ICA KW - Kern-PCA KW - Kernmethoden KW - ICA KW - reliability assessment KW - robust ICA KW - overcomplete ICA KW - outlier detection KW - nonlinear ICA KW - kernel PCA KW - kernel methods Y1 - 2004 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-0001540 ER - TY - THES A1 - Dietze, Stefan T1 - Modell und Optimierungsansatz für Open Source Softwareentwicklungsprozesse N2 - Gerade in den letzten Jahren erfuhr Open Source Software (OSS) eine zunehmende Verbreitung und Popularität und hat sich in verschiedenen Anwendungsdomänen etabliert. Die Prozesse, welche sich im Kontext der OSS-Entwicklung (auch: OSSD – Open Source Software-Development) evolutionär herausgebildet haben, weisen in den verschiedenen OSS-Entwicklungsprojekten z.T. ähnliche Eigenschaften und Strukturen auf und auch die involvierten Entitäten, wie z.B. Artefakte, Rollen oder Software-Werkzeuge sind weitgehend miteinander vergleichbar. Dies motiviert den Gedanken, ein verallgemeinerbares Modell zu entwickeln, welches die generalisierbaren Entwicklungsprozesse im Kontext von OSS zu einem übertragbaren Modell abstrahiert. Auch in der Wissenschaftsdisziplin des Software Engineering (SE) wurde bereits erkannt, dass sich der OSSD-Ansatz in verschiedenen Aspekten erheblich von klassischen (proprietären) Modellen des SE unterscheidet und daher diese Methoden einer eigenen wissenschaftlichen Betrachtung bedürfen. In verschiedenen Publikationen wurden zwar bereits einzelne Aspekte der OSS-Entwicklung analysiert und Theorien über die zugrundeliegenden Entwicklungsmethoden formuliert, aber es existiert noch keine umfassende Beschreibung der typischen Prozesse der OSSD-Methodik, die auf einer empirischen Untersuchung existierender OSS-Entwicklungsprojekte basiert. Da dies eine Voraussetzung für die weitere wissenschaftliche Auseinandersetzung mit OSSD-Prozessen darstellt, wird im Rahmen dieser Arbeit auf der Basis vergleichender Fallstudien ein deskriptives Modell der OSSD-Prozesse hergeleitet und mit Modellierungselementen der UML formalisiert beschrieben. Das Modell generalisiert die identifizierten Prozesse, Prozessentitäten und Software-Infrastrukturen der untersuchten OSSD-Projekte. Es basiert auf einem eigens entwickelten Metamodell, welches die zu analysierenden Entitäten identifiziert und die Modellierungssichten und -elemente beschreibt, die zur UML-basierten Beschreibung der Entwicklungsprozesse verwendet werden. In einem weiteren Arbeitsschritt wird eine weiterführende Analyse des identifizierten Modells durchgeführt, um Implikationen, und Optimierungspotentiale aufzuzeigen. Diese umfassen beispielsweise die ungenügende Plan- und Terminierbarkeit von Prozessen oder die beobachtete Tendenz von OSSD-Akteuren, verschiedene Aktivitäten mit unterschiedlicher Intensität entsprechend der subjektiv wahrgenommenen Anreize auszuüben, was zur Vernachlässigung einiger Prozesse führt. Anschließend werden Optimierungszielstellungen dargestellt, die diese Unzulänglichkeiten adressieren, und ein Optimierungsansatz zur Verbesserung des OSSD-Modells wird beschrieben. Dieser Ansatz umfasst die Erweiterung der identifizierten Rollen, die Einführung neuer oder die Erweiterung bereits identifizierter Prozesse und die Modifikation oder Erweiterung der Artefakte des generalisierten OSS-Entwicklungsmodells. Die vorgestellten Modellerweiterungen dienen vor allem einer gesteigerten Qualitätssicherung und der Kompensation von vernachlässigten Prozessen, um sowohl die entwickelte Software- als auch die Prozessqualität im OSSD-Kontext zu verbessern. Desweiteren werden Softwarefunktionalitäten beschrieben, welche die identifizierte bestehende Software-Infrastruktur erweitern und eine gesamtheitlichere, softwaretechnische Unterstützung der OSSD-Prozesse ermöglichen sollen. Abschließend werden verschiedene Anwendungsszenarien der Methoden des OSS-Entwicklungsmodells, u.a. auch im kommerziellen SE, identifiziert und ein Implementierungsansatz basierend auf der OSS GENESIS vorgestellt, der zur Implementierung und Unterstützung des OSSD-Modells verwendet werden kann. N2 - In recent years Open Source Software (OSS) has become more widespread and its popularity has grown so that it is now established in various application domains. The processes which have emerged evolutionarily within the context of OSS development (OSSD – Open Source Software Development) display, to some extent, similar properties and structures in the various OSSD projects. The involved entities, e.g., artifacts, roles or software tools, are also widely comparable. This leads to the idea of developing a generalizable model which abstracts the generalizable development processes within the context of OSS to a transferable model. Even the scientific discipline of Software Engineering (SE) has recognized that the OSSD approach is, in various aspects, considerably different from traditional (proprietary) models of SE, and that these methods therefore require their own scientific consideration. Numerous publications have already analyzed individual aspects of OSSD and formulated theories about the fundamental development methods, but to date there is still no comprehensive description of the typical processes of OSSD methodology based on an empirical study of existing OSSD projects. Since this is a precondition for the further scientific examination of OSSD processes, a descriptive model of OSSD processes is obtained on the basis of comparative case studies and described in a formalized manner with UML modeling elements within the context of this dissertation. The model generalizes the identified processes, process entities and software infrastructures of the analyzed OSSD projects. It is based on a specially developed meta model which identifies the entities to be analyzed and describes the modeling viewpoints and elements which are used for the UML-based description of the development processes. Another procedure step includes the further analysis of the identified model in order to display the implications, and the potential for optimization. For example, these encompass the insufficient planning and scheduling capability of processes or the observed tendency of OSSD actors to carry out various activities at different intensities depending on the subjectively perceived incentives which leads to some processes being neglected. Subsequently, the optimization targets which address these inadequacies are displayed, and an optimization approach for the improvement of the OSSD model is described. The approach incorporates the expansion of the identified roles, the introduction of new or the expansion of already identified processes and the modification or expansion of artifacts of the generalized OSSD model. The presented model enhancements serve, above all, to increase quality assurance and to compensate neglected processes in order to improve developed software quality as well as process quality in the context of OSSD. Furthermore, software functionalities are described which expand the existing identified software infrastructure and should enable an overall, software-technical support of OSSD processes. Finally, the various application scenarios of OSSD model methods - also in commercial SE - are identified and an implementation approach based on the OSS GENESIS is presented which can be used to implement and support the OSSD model. T2 - Modell und Optimierungsansatz für Open Source Softwareentwicklungsprozesse KW - Prozessmodell KW - Software Engineering KW - Open Source KW - Prozessmodellierung KW - Metamodell KW - Softwareentwicklung KW - Prozess Verbesserung KW - process model KW - software engineering KW - open source KW - process modelling KW - meta model KW - software development KW - process improvement Y1 - 2004 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-0001594 ER - TY - THES A1 - Knöpfel, Andreas T1 - Konzepte der Beschreibung interaktiver Systeme T1 - Concepts of describing interactive systems N2 - Interaktive System sind dynamische Systeme mit einem zumeist informationellen Kern, die über eine Benutzungsschnittstelle von einem oder mehreren Benutzern bedient werden können. Grundlage für die Benutzung interaktiver Systeme ist das Verständnis von Zweck und Funktionsweise. Allein aus Form und Gestalt der Benutzungsschnittstelle ergibt sich ein solches Verständnis nur in einfachen Fällen. Mit steigender Komplexität ist daher eine verständliche Beschreibung solcher Systeme für deren Entwicklung und Benutzung unverzichtbar. Abhängig von ihrem Zweck variieren die Formen vorgefundener Beschreibungen in der Literatur sehr stark. Ausschlaggebend für die Verständlichkeit einer Beschreibung ist jedoch primär die ihr zugrundeliegende Begriffswelt. Zur Beschreibung allgemeiner komplexer diskreter Systeme - aufbauend auf einer getrennten Betrachtung von Aufbau-, Ablauf- und Wertestrukturen - existiert eine bewährte Begriffswelt. Eine Spezialisierung dieser Begriffs- und Vorstellungswelt, die den unterschiedlichen Betrachtungsebenen interaktiver Systeme gerecht wird und die als Grundlage beliebiger Beschreibungsansätze interaktiver Systeme dienen kann, gibt es bisher nicht. Ziel dieser Arbeit ist die Bereitstellung einer solchen Begriffswelt zur effizienten Kommunikation der Strukturen interaktiver Systeme. Dadurch soll die Grundlage für eine sinnvolle Ergänzung bestehender Beschreibungs- und Entwicklungsansätze geschaffen werden. Prinzipien der Gestaltung von Benutzungsschnittstellen, Usability- oder Ergonomiebetrachtungen stehen nicht im Mittelpunkt der Arbeit. Ausgehend von der informationellen Komponente einer Benutzungsschnittstelle werden drei Modellebenen abgegrenzt, die bei der Betrachtung eines interaktiven Systems zu unterscheiden sind. Jede Modellebene ist durch eine typische Begriffswelt gekennzeichnet, die ihren Ursprung in einer aufbauverwurzelten Vorstellung hat. Der durchgängige Bezug auf eine Systemvorstellung unterscheidet diesen Ansatz von dem bereits bekannten Konzept der Abgrenzung unterschiedlicher Ebenen verschiedenartiger Entwurfsentscheidungen. Die Fundamental Modeling Concepts (FMC) bilden dabei die Grundlage für die Findung und die Darstellung von Systemstrukturen. Anhand bestehender Systembeschreibungen wird gezeigt, wie die vorgestellte Begriffswelt zur Modellfindung genutzt werden kann. Dazu wird eine repräsentative Auswahl vorgefundener Systembeschreibungen aus der einschlägigen Literatur daraufhin untersucht, in welchem Umfang durch sie die Vorstellungswelt dynamischer Systeme zum Ausdruck kommt. Defizite in der ursprünglichen Darstellung werden identifiziert. Anhand von Alternativmodellen zu den betrachteten Systemen wird der Nutzen der vorgestellten Begriffswelt und Darstellungsweise demonstriert. N2 - Interactive systems are dynamic systems which provide services to one or more users via a user interface. Many of these systems have an information processing core. To effectively use such a system, a user needs to know about the purpose and functional concepts of the system. Only in case of a rather simple functionality, the required knowledge is likely to be obtained by mere exploration of the user interface. For complex systems, a comprehensive description is essential for effective and efficient operation, but also for system development. Especially in the context of this publication, the focus is on the diagrams that are used for communication in the development process of interactive systems. With regard to its purpose these descriptions vary in form and notation. In any case, it is the underlying terminology which is crucial to the understandability. Established concepts and notations for the description of generic information processing systems promote a strict separation of three categories of system structures: Compositional structures, behavioral structures and value-range structures. This publication suggests a specialization of this approach for the description of interactive systems. The definition of specific notions and semantic layers is intended to provide a complement to existing description approaches in that field that constitutes a mental framework to enhance the efficiency of communication about interactive systems. In focusing to the description aspect only, design principles, system architectures and development methods are the context but not the subject of this work. The separation of three semantic layers provides the foundation to distinguish purpose-related, interaction-related and implementation-related models of interactive systems. Each semantic layer is characterized by a specific terminology. Referring to the idea of equivalent models, the compositional system structure varies from layer to layer and provides the framework to ask for the observable behavior and values. The strict assignment of system aspects to system components distinguishes this approach from a simple layering of design decisions in the development of interactive systems as commonly found in the relevant literature. The Fundamental Modeling Concepts (FMC) provide the foundation for the identification and representation of system structures. A selection of system descriptions taken from the relevant literature provides the starting point to demonstrate the application of the suggested concept. Purpose, content and form of each example are analyzed with regard to the implied system structure. Weaknesses in the original representation are identified. Alternative models complement the examples to illustrate the benefit of the new approach. KW - Systementwurf KW - Benutzeroberfläche KW - Modellierung KW - Interaktives System KW - Systemstruktur KW - FMC KW - Betrachtungsebenen KW - Interactive system KW - model-driven architecture KW - FMC Y1 - 2004 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-2898 ER - TY - THES A1 - Gröne, Bernhard T1 - Konzeptionelle Patterns und ihre Darstellung N2 - Zur Beherrschung großer Systeme, insbesondere zur Weitergabe und Nutzung von Erfahrungswissen in der frühen Entwurfs- und Planungsphase, benötigt man Abstraktionen für deren Strukturen. Trennt man Software- von Systemstrukturen, kann man mit letzteren Systeme auf ausreichend hohem Abstraktionsgrad beschreiben.Software-Patterns dienen dazu, Erfahrungswissen bezüglich programmierter Systeme strukturiert weiterzugeben. Dabei wird unterschieden zwischen Idiomen, die sich auf Lösungen mit einer bestimmten Programmiersprache beziehen, Design-Patterns, die nur einen kleinen Teil des Programms betreffen und Architektur-Patterns, deren Einfluss über einen größeren Teil oder gar das komplette Programm reicht. Eine Untersuchung von existierenden Patterns zeigt, dass deren Konzepte nützlich zum Finden von Systemstrukturen sind. Die grafische Darstellung dieser Patterns ist dagegen oft auf Software-Strukturen eingeschränkt und ist für die Vermittlung von Erfahrungen zum Finden von Systemstrukturen meist nicht geeignet. Daher wird die Kategorie der konzeptionellen Patterns mit einer darauf abgestimmten grafischen Darstellungsform vorgeschlagen, bei denen Problem und Lösungsvorschlag im Bereich der Systemstrukturen liegen. Sie betreffen informationelle Systeme, sind aber nicht auf Lösungen mit Software beschränkt. Die Systemstrukturen werden grafisch dargestellt, wobei dafür die Fundamental Modeling Concepts (FMC) verwendet werden, die zur Darstellung von Systemstrukturen entwickelt wurden. N2 - Planning large and complex software systems is an important task of a system architect. It includes communicating with the customer, planning the overall system structure as well as preparing the division of labor among software engineers. What's more, a system architect benefits from other professionals' experiences concerning system architecture. By separating system from software structures, one can now describe a system by its system structure on an adequate level of abstraction. Patterns provide a common form for the transfer of experiences. A pattern describes a widely used and proven solution to a problem that occurs in a certain context. A study of existing architectural and design patterns shows that the concepts of many patterns carry valuable experiences concerning finding system structures. On the other hand, the graphical representations of these patterns usually focus on the software structures resulting from the solution in terms of classes and their relationships. This can be a problem if the solution doesn't imply one specific software structure but rather describes a concept which may be even independent from an implementation via software at all.For that reason, Conceptual Patterns are introduced. A pattern can be called conceptual if both problem and solution concern system structures. Here, the functional aspects and structures of the system are relevant while code structures or even the use of software for implementation are not. To support the focus on system structures, terminology and notation of conceptual patterns should use an adequate means such as provided by the Fundamental Modeling Concepts (FMC). KW - Patterns KW - Systemstruktur KW - FMC KW - Konzeptionell KW - Patterns KW - System structure KW - FMC KW - Conceptual Y1 - 2004 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-2302 ER - TY - JOUR A1 - Scheffler, Thomas A1 - Schnor, Bettina T1 - Securing Next generation Mobile Networks Y1 - 2004 SN - 0-86341-388-9 ER - TY - JOUR A1 - Friedrich, Sven A1 - Krahmer, Sebastian A1 - Schneidenbach, Lars A1 - Schnor, Bettina T1 - Loaded : Server Load Balancing for IPv6 Y1 - 2004 ER - TY - JOUR A1 - Vandenhouten, Ralf A1 - Behrens, Thomas A1 - Schnor, Bettina T1 - Entwicklung eines Gatewaysystems für telematikbasiertes Gerätemonitoring Y1 - 2004 SN - 0949-8214 ER - TY - BOOK A1 - Feider, Henryk A1 - Schnor, Bettina T1 - PCG-Agreement Dokument T3 - Technischer Bericht Y1 - 2004 SN - 0946-7580 PB - Universität Potsdam, Institut für Informatik CY - Potsdam ER - TY - BOOK A1 - Mihahn, Michael A1 - Schnor, Bettina T1 - Fault-Tolerant Grid Peer Services T3 - Technischer Bericht Y1 - 2004 SN - 0946-7580 PB - Universität Potsdam, Institut für Informatik CY - Potsdam ER -