@phdthesis{Heinze2015, author = {Heinze, Theodor}, title = {Analyse von Patientendaten und Entscheidungsunterst{\"u}tzung in der Telemedizin}, school = {Universit{\"a}t Potsdam}, pages = {173}, year = {2015}, language = {de} } @inproceedings{HeinischRomeikeKnobelsdorfetal.2013, author = {Heinisch, Isabelle and Romeike, Ralf and Knobelsdorf, Maria and Kreitz, Christoph and Nyl{\´e}n, Aletta and D{\"o}rge, Christina and G{\"o}ttel, Timo and Holz, Jan and Bergner, Nadine and Schroeder, Ulrik and Metzger, Christiane and Haag, Johann and Abke, J{\"o}rg and Schwirtlich, Vincent and Sedelmaier, Yvonne and M{\"u}ller, Dorothee and Frommer, Andreas and Humbert, Ludger and Berges, Marc and M{\"u}hling, Andreas and Hubwieser, Peter and Steuer, Horst and Engbring, Dieter and Selke, Harald and Drews, Paul and Schirmer, Ingrid and Morisse, Marcel and Sagawe, Arno and Rolf, Arno and Friedemann, Stefan and Gr{\"o}ger, Stefan and Schumann, Matthias and Klinger, Melanie and Polutina, Olena and Bibel, Ariane and G{\"o}tz, Christian and Brinda, Torsten and Apel, Rebecca and Berg, Tobias and Bergner, Nadine and Chatti, Mohamed Amine and Leicht-Scholten, Carmen and Schroeder, Ulrik and Al-Saffar, Loay Talib and Petre, Marian and Schirmer, Ingrid and Rick, Detlef}, title = {HDI 2012 - Informatik f{\"u}r eine nachhaltige Zukunft : 5. Fachtagung Hochschuldidaktik der Informatik ; 06.-07. November 2012, Universit{\"a}t Hamburg}, editor = {Forbrig, Peter and Rick, Detlef and Schmolitzky, Axel}, publisher = {Universit{\"a}tsverlag Potsdam}, address = {Potsdam}, isbn = {978-3-86956-220-9}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-62891}, pages = {169}, year = {2013}, abstract = {Die Tagungsreihe zur Hochschuldidaktik der Informatik HDI wird vom Fachbereich Informatik und Ausbildung / Didaktik der Informatik (IAD) in der Gesellschaft f{\"u}r Informatik e. V. (GI) organisiert. Sie dient den Lehrenden der Informatik in Studieng{\"a}ngen an Hochschulen als Forum der Information und des Austauschs {\"u}ber neue didaktische Ans{\"a}tze und bildungspolitische Themen im Bereich der Hochschulausbildung aus der fachlichen Perspektive der Informatik. Diese f{\"u}nfte HDI 2012 wurde an der Universit{\"a}t Hamburg organisiert. F{\"u}r sie wurde das spezielle Motto „Informatik f{\"u}r eine nachhaltige Zukunft" gew{\"a}hlt, um insbesondere Fragen der Bildungsrelevanz informatischer Inhalte, der Kompetenzen f{\"u}r Studierende informatisch gepr{\"a}gter Studieng{\"a}nge und der Rolle der Informatik in der Hochschulentwicklung zu diskutieren.}, language = {de} } @phdthesis{Hecher2021, author = {Hecher, Markus}, title = {Advanced tools and methods for treewidth-based problem solving}, doi = {10.25932/publishup-51251}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-512519}, school = {Universit{\"a}t Potsdam}, pages = {xv, 184}, year = {2021}, abstract = {In the last decades, there was a notable progress in solving the well-known Boolean satisfiability (Sat) problem, which can be witnessed by powerful Sat solvers. One of the reasons why these solvers are so fast are structural properties of instances that are utilized by the solver's interna. This thesis deals with the well-studied structural property treewidth, which measures the closeness of an instance to being a tree. In fact, there are many problems parameterized by treewidth that are solvable in polynomial time in the instance size when parameterized by treewidth. In this work, we study advanced treewidth-based methods and tools for problems in knowledge representation and reasoning (KR). Thereby, we provide means to establish precise runtime results (upper bounds) for canonical problems relevant to KR. Then, we present a new type of problem reduction, which we call decomposition-guided (DG) that allows us to precisely monitor the treewidth when reducing from one problem to another problem. This new reduction type will be the basis for a long-open lower bound result for quantified Boolean formulas and allows us to design a new methodology for establishing runtime lower bounds for problems parameterized by treewidth. Finally, despite these lower bounds, we provide an efficient implementation of algorithms that adhere to treewidth. Our approach finds suitable abstractions of instances, which are subsequently refined in a recursive fashion, and it uses Sat solvers for solving subproblems. It turns out that our resulting solver is quite competitive for two canonical counting problems related to Sat.}, language = {en} } @article{HaubeltNeubauerSchaubetal.2018, author = {Haubelt, Christian and Neubauer, Kai and Schaub, Torsten and Wanko, Philipp}, title = {Design space exploration with answer set programming}, series = {K{\"u}nstliche Intelligenz}, volume = {32}, journal = {K{\"u}nstliche Intelligenz}, number = {2-3}, publisher = {Springer}, address = {Heidelberg}, issn = {0933-1875}, doi = {10.1007/s13218-018-0530-3}, pages = {205 -- 206}, year = {2018}, abstract = {The aim of our project design space exploration with answer set programming is to develop a general framework based on Answer Set Programming (ASP) that finds valid solutions to the system design problem and simultaneously performs Design Space Exploration (DSE) to find the most favorable alternatives. We leverage recent developments in ASP solving that allow for tight integration of background theories to create a holistic framework for effective DSE.}, language = {en} } @phdthesis{Harmeling2004, author = {Harmeling, Stefan}, title = {Independent component analysis and beyond}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-0001540}, school = {Universit{\"a}t Potsdam}, year = {2004}, abstract = {'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 n{\"u}tzlich ist, gibt es viele Anwendungen, die Erweiterungen von ICA erfordern. In dieser Dissertation pr{\"a}sentieren wir neue Verfahren, die die Funktionalit{\"a}t von ICA erweitern: (1) Zuverl{\"a}ssigkeitsanalyse und Gruppierung von unabh{\"a}ngigen Komponenten durch Hinzuf{\"u}gen von Rauschen, (2) robuste und {\"u}berbestimmte ('over-complete') ICA durch Ausreissererkennung, und (3) nichtlineare ICA mit Kernmethoden.}, language = {en} } @phdthesis{Haider2013, author = {Haider, Peter}, title = {Prediction with Mixture Models}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-69617}, school = {Universit{\"a}t Potsdam}, year = {2013}, abstract = {Learning a model for the relationship between the attributes and the annotated labels of data examples serves two purposes. Firstly, it enables the prediction of the label for examples without annotation. Secondly, the parameters of the model can provide useful insights into the structure of the data. If the data has an inherent partitioned structure, it is natural to mirror this structure in the model. Such mixture models predict by combining the individual predictions generated by the mixture components which correspond to the partitions in the data. Often the partitioned structure is latent, and has to be inferred when learning the mixture model. Directly evaluating the accuracy of the inferred partition structure is, in many cases, impossible because the ground truth cannot be obtained for comparison. However it can be assessed indirectly by measuring the prediction accuracy of the mixture model that arises from it. This thesis addresses the interplay between the improvement of predictive accuracy by uncovering latent cluster structure in data, and further addresses the validation of the estimated structure by measuring the accuracy of the resulting predictive model. In the application of filtering unsolicited emails, the emails in the training set are latently clustered into advertisement campaigns. Uncovering this latent structure allows filtering of future emails with very low false positive rates. In order to model the cluster structure, a Bayesian clustering model for dependent binary features is developed in this thesis. Knowing the clustering of emails into campaigns can also aid in uncovering which emails have been sent on behalf of the same network of captured hosts, so-called botnets. This association of emails to networks is another layer of latent clustering. Uncovering this latent structure allows service providers to further increase the accuracy of email filtering and to effectively defend against distributed denial-of-service attacks. To this end, a discriminative clustering model is derived in this thesis that is based on the graph of observed emails. The partitionings inferred using this model are evaluated through their capacity to predict the campaigns of new emails. Furthermore, when classifying the content of emails, statistical information about the sending server can be valuable. Learning a model that is able to make use of it requires training data that includes server statistics. In order to also use training data where the server statistics are missing, a model that is a mixture over potentially all substitutions thereof is developed. Another application is to predict the navigation behavior of the users of a website. Here, there is no a priori partitioning of the users into clusters, but to understand different usage scenarios and design different layouts for them, imposing a partitioning is necessary. The presented approach simultaneously optimizes the discriminative as well as the predictive power of the clusters. Each model is evaluated on real-world data and compared to baseline methods. The results show that explicitly modeling the assumptions about the latent cluster structure leads to improved predictions compared to the baselines. It is beneficial to incorporate a small number of hyperparameters that can be tuned to yield the best predictions in cases where the prediction accuracy can not be optimized directly.}, language = {en} } @phdthesis{Hagedorn2016, author = {Hagedorn, Benjamin}, title = {Konzepte und Techniken zur servicebasierten Visualisierung von geovirtuellen 3D-Umgebungen}, school = {Universit{\"a}t Potsdam}, pages = {140}, year = {2016}, language = {de} } @phdthesis{Groene2004, author = {Gr{\"o}ne, Bernhard}, title = {Konzeptionelle Patterns und ihre Darstellung}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-2302}, school = {Universit{\"a}t Potsdam}, pages = {vii ; 120}, year = {2004}, abstract = {Zur Beherrschung großer Systeme, insbesondere zur Weitergabe und Nutzung von Erfahrungswissen in der fr{\"u}hen Entwurfs- und Planungsphase, ben{\"o}tigt man Abstraktionen f{\"u}r deren Strukturen. Trennt man Software- von Systemstrukturen, kann man mit letzteren Systeme auf ausreichend hohem Abstraktionsgrad beschreiben.Software-Patterns dienen dazu, Erfahrungswissen bez{\"u}glich programmierter Systeme strukturiert weiterzugeben. Dabei wird unterschieden zwischen Idiomen, die sich auf L{\"o}sungen mit einer bestimmten Programmiersprache beziehen, Design-Patterns, die nur einen kleinen Teil des Programms betreffen und Architektur-Patterns, deren Einfluss {\"u}ber einen gr{\"o}ßeren Teil oder gar das komplette Programm reicht. Eine Untersuchung von existierenden Patterns zeigt, dass deren Konzepte n{\"u}tzlich zum Finden von Systemstrukturen sind. Die grafische Darstellung dieser Patterns ist dagegen oft auf Software-Strukturen eingeschr{\"a}nkt und ist f{\"u}r 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 L{\"o}sungsvorschlag im Bereich der Systemstrukturen liegen. Sie betreffen informationelle Systeme, sind aber nicht auf L{\"o}sungen mit Software beschr{\"a}nkt. Die Systemstrukturen werden grafisch dargestellt, wobei daf{\"u}r die Fundamental Modeling Concepts (FMC) verwendet werden, die zur Darstellung von Systemstrukturen entwickelt wurden.}, language = {de} } @phdthesis{Glander2012, author = {Glander, Tassilo}, title = {Multi-scale representations of virtual 3D city models}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-64117}, school = {Universit{\"a}t Potsdam}, year = {2012}, abstract = {Virtual 3D city and landscape models are the main subject investigated in this thesis. They digitally represent urban space and have many applications in different domains, e.g., simulation, cadastral management, and city planning. Visualization is an elementary component of these applications. Photo-realistic visualization with an increasingly high degree of detail leads to fundamental problems for comprehensible visualization. A large number of highly detailed and textured objects within a virtual 3D city model may create visual noise and overload the users with information. Objects are subject to perspective foreshortening and may be occluded or not displayed in a meaningful way, as they are too small. In this thesis we present abstraction techniques that automatically process virtual 3D city and landscape models to derive abstracted representations. These have a reduced degree of detail, while essential characteristics are preserved. After introducing definitions for model, scale, and multi-scale representations, we discuss the fundamentals of map generalization as well as techniques for 3D generalization. The first presented technique is a cell-based generalization of virtual 3D city models. It creates abstract representations that have a highly reduced level of detail while maintaining essential structures, e.g., the infrastructure network, landmark buildings, and free spaces. The technique automatically partitions the input virtual 3D city model into cells based on the infrastructure network. The single building models contained in each cell are aggregated to abstracted cell blocks. Using weighted infrastructure elements, cell blocks can be computed on different hierarchical levels, storing the hierarchy relation between the cell blocks. Furthermore, we identify initial landmark buildings within a cell by comparing the properties of individual buildings with the aggregated properties of the cell. For each block, the identified landmark building models are subtracted using Boolean operations and integrated in a photo-realistic way. Finally, for the interactive 3D visualization we discuss the creation of the virtual 3D geometry and their appearance styling through colors, labeling, and transparency. We demonstrate the technique with example data sets. Additionally, we discuss applications of generalization lenses and transitions between abstract representations. The second technique is a real-time-rendering technique for geometric enhancement of landmark objects within a virtual 3D city model. Depending on the virtual camera distance, landmark objects are scaled to ensure their visibility within a specific distance interval while deforming their environment. First, in a preprocessing step a landmark hierarchy is computed, this is then used to derive distance intervals for the interactive rendering. At runtime, using the virtual camera distance, a scaling factor is computed and applied to each landmark. The scaling factor is interpolated smoothly at the interval boundaries using cubic B{\´e}zier splines. Non-landmark geometry that is near landmark objects is deformed with respect to a limited number of landmarks. We demonstrate the technique by applying it to a highly detailed virtual 3D city model and a generalized 3D city model. In addition we discuss an adaptation of the technique for non-linear projections and mobile devices. The third technique is a real-time rendering technique to create abstract 3D isocontour visualization of virtual 3D terrain models. The virtual 3D terrain model is visualized as a layered or stepped relief. The technique works without preprocessing and, as it is implemented using programmable graphics hardware, can be integrated with minimal changes into common terrain rendering techniques. Consequently, the computation is done in the rendering pipeline for each vertex, primitive, i.e., triangle, and fragment. For each vertex, the height is quantized to the nearest isovalue. For each triangle, the vertex configuration with respect to their isovalues is determined first. Using the configuration, the triangle is then subdivided. The subdivision forms a partial step geometry aligned with the triangle. For each fragment, the surface appearance is determined, e.g., depending on the surface texture, shading, and height-color-mapping. Flexible usage of the technique is demonstrated with applications from focus+context visualization, out-of-core terrain rendering, and information visualization. This thesis presents components for the creation of abstract representations of virtual 3D city and landscape models. Re-using visual language from cartography, the techniques enable users to build on their experience with maps when interpreting these representations. Simultaneously, characteristics of 3D geovirtual environments are taken into account by addressing and discussing, e.g., continuous scale, interaction, and perspective.}, language = {en} } @article{GianniniRichterServettoetal.2018, author = {Giannini, Paola and Richter, Tim and Servetto, Marco and Zucca, Elena}, title = {Tracing sharing in an imperative pure calculus}, series = {Science of computer programming}, volume = {172}, journal = {Science of computer programming}, publisher = {Elsevier}, address = {Amsterdam}, issn = {0167-6423}, doi = {10.1016/j.scico.2018.11.007}, pages = {180 -- 202}, year = {2018}, abstract = {We introduce a type and effect system, for an imperative object calculus, which infers sharing possibly introduced by the evaluation of an expression, represented as an equivalence relation among its free variables. This direct representation of sharing effects at the syntactic level allows us to express in a natural way, and to generalize, widely-used notions in literature, notably uniqueness and borrowing. Moreover, the calculus is pure in the sense that reduction is defined on language terms only, since they directly encode store. The advantage of this non-standard execution model with respect to a behaviorally equivalent standard model using a global auxiliary structure is that reachability relations among references are partly encoded by scoping. (C) 2018 Elsevier B.V. All rights reserved.}, language = {en} } @phdthesis{Ghasemzadeh2005, author = {Ghasemzadeh, Mohammad}, title = {A new algorithm for the quantified satisfiability problem, based on zero-suppressed binary decision diagrams and memoization}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-6378}, school = {Universit{\"a}t Potsdam}, year = {2005}, abstract = {Quantified Boolean formulas (QBFs) play an important role in theoretical computer science. QBF extends propositional logic in such a way that many advanced forms of reasoning can be easily formulated and evaluated. In this dissertation we present our ZQSAT, which is an algorithm for evaluating quantified Boolean formulas. ZQSAT is based on ZBDD: Zero-Suppressed Binary Decision Diagram , which is a variant of BDD, and an adopted version of the DPLL algorithm. It has been implemented in C using the CUDD: Colorado University Decision Diagram package. The capability of ZBDDs in storing sets of subsets efficiently enabled us to store the clauses of a QBF very compactly and let us to embed the notion of memoization to the DPLL algorithm. These points led us to implement the search algorithm in such a way that we could store and reuse the results of all previously solved subformulas with a little overheads. ZQSAT can solve some sets of standard QBF benchmark problems (known to be hard for DPLL based algorithms) faster than the best existing solvers. In addition to prenex-CNF, ZQSAT accepts prenex-NNF formulas. We show and prove how this capability can be exponentially beneficial.}, subject = {Bin{\"a}res Entscheidungsdiagramm}, language = {en} } @article{GebserKaminskiKaufmannetal.2018, author = {Gebser, Martin and Kaminski, Roland and Kaufmann, Benjamin and L{\"u}hne, Patrick and Obermeier, Philipp and Ostrowski, Max and Romero Davila, Javier and Schaub, Torsten and Schellhorn, Sebastian and Wanko, Philipp}, title = {The Potsdam Answer Set Solving Collection 5.0}, series = {K{\"u}nstliche Intelligenz}, volume = {32}, journal = {K{\"u}nstliche Intelligenz}, number = {2-3}, publisher = {Springer}, address = {Heidelberg}, issn = {0933-1875}, doi = {10.1007/s13218-018-0528-x}, pages = {181 -- 182}, year = {2018}, abstract = {The Potsdam answer set solving collection, or Potassco for short, bundles various tools implementing and/or applying answer set programming. The article at hand succeeds an earlier description of the Potassco project published in Gebser et al. (AI Commun 24(2):107-124, 2011). Hence, we concentrate in what follows on the major features of the most recent, fifth generation of the ASP system clingo and highlight some recent resulting application systems.}, language = {en} } @phdthesis{Gebser2011, author = {Gebser, Martin}, title = {Proof theory and algorithms for answer set programming}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-55425}, school = {Universit{\"a}t Potsdam}, year = {2011}, abstract = {Answer Set Programming (ASP) is an emerging paradigm for declarative programming, in which a computational problem is specified by a logic program such that particular models, called answer sets, match solutions. ASP faces a growing range of applications, demanding for high-performance tools able to solve complex problems. ASP integrates ideas from a variety of neighboring fields. In particular, automated techniques to search for answer sets are inspired by Boolean Satisfiability (SAT) solving approaches. While the latter have firm proof-theoretic foundations, ASP lacks formal frameworks for characterizing and comparing solving methods. Furthermore, sophisticated search patterns of modern SAT solvers, successfully applied in areas like, e.g., model checking and verification, are not yet established in ASP solving. We address these deficiencies by, for one, providing proof-theoretic frameworks that allow for characterizing, comparing, and analyzing approaches to answer set computation. For another, we devise modern ASP solving algorithms that integrate and extend state-of-the-art techniques for Boolean constraint solving. We thus contribute to the understanding of existing ASP solving approaches and their interconnections as well as to their enhancement by incorporating sophisticated search patterns. The central idea of our approach is to identify atomic as well as composite constituents of a propositional logic program with Boolean variables. This enables us to describe fundamental inference steps, and to selectively combine them in proof-theoretic characterizations of various ASP solving methods. In particular, we show that different concepts of case analyses applied by existing ASP solvers implicate mutual exponential separations regarding their best-case complexities. We also develop a generic proof-theoretic framework amenable to language extensions, and we point out that exponential separations can likewise be obtained due to case analyses on them. We further exploit fundamental inference steps to derive Boolean constraints characterizing answer sets. They enable the conception of ASP solving algorithms including search patterns of modern SAT solvers, while also allowing for direct technology transfers between the areas of ASP and SAT solving. Beyond the search for one answer set of a logic program, we address the enumeration of answer sets and their projections to a subvocabulary, respectively. The algorithms we develop enable repetition-free enumeration in polynomial space without being intrusive, i.e., they do not necessitate any modifications of computations before an answer set is found. Our approach to ASP solving is implemented in clasp, a state-of-the-art Boolean constraint solver that has successfully participated in recent solver competitions. Although we do here not address the implementation techniques of clasp or all of its features, we present the principles of its success in the context of ASP solving.}, language = {en} } @article{GautamZhangLandwehretal.2021, author = {Gautam, Khem Raj and Zhang, Guoqiang and Landwehr, Niels and Adolphs, Julian}, title = {Machine learning for improvement of thermal conditions inside a hybrid ventilated animal building}, series = {Computers and electronics in agriculture : COMPAG online ; an international journal}, volume = {187}, journal = {Computers and electronics in agriculture : COMPAG online ; an international journal}, publisher = {Elsevier Science}, address = {Amsterdam [u.a.]}, issn = {0168-1699}, doi = {10.1016/j.compag.2021.106259}, pages = {10}, year = {2021}, abstract = {In buildings with hybrid ventilation, natural ventilation opening positions (windows), mechanical ventilation rates, heating, and cooling are manipulated to maintain desired thermal conditions. The indoor temperature is regulated solely by ventilation (natural and mechanical) when the external conditions are favorable to save external heating and cooling energy. The ventilation parameters are determined by a rule-based control scheme, which is not optimal. This study proposes a methodology to enable real-time optimum control of ventilation parameters. We developed offline prediction models to estimate future thermal conditions from the data collected from building in operation. The developed offline model is then used to find the optimal controllable ventilation parameters in real-time to minimize the setpoint deviation in the building. With the proposed methodology, the experimental building's setpoint deviation improved for 87\% of time, on average, by 0.53 degrees C compared to the current deviations.}, language = {en} } @phdthesis{Fudickar2014, author = {Fudickar, Sebastian}, title = {Sub Ghz transceiver for indoor localisation of smartphones}, school = {Universit{\"a}t Potsdam}, pages = {IV, 167}, year = {2014}, language = {en} } @inproceedings{FroitzheimBergnerSchroederetal.2015, author = {Froitzheim, Manuel and Bergner, Nadine and Schroeder, Ulrik and Hurtienne, Dominik and Spannagel, Christian and Roderus, Simon and Wienkop, Uwe and Leonhardt, Thiemo and Kwiecien, Alexandra and Schmetz, Arno and Bellgardt, Martin and Naumann, Uwe and Weßels, Doris and Metzger, Christiane and L{\"a}ngrich, Matthias and Schulze, J{\"o}rg and Jakoblew, Marcel and Keil, Reinhard and Winkelnkemper, Felix and Engbring, Dieter and Klar, Tilman-Mathies and Kujath, Bertold and Sch{\"u}tze, Christopher and Fietkau, Julian and Kindsm{\"u}ller, Martin Christof and G{\"o}ttel, Timo and Bergner, Nadine and Taraschewski, Christian and Vosseberg, Karin and Czernik, Sofie and Erb, Ulrike and Vielhaber, Michael and Schlierkamp, Kathrin and Thurner, Veronika and Br{\"o}ker, Kathrin}, title = {HDI 2014 - Gestalten von {\"U}berg{\"a}ngen}, editor = {Forbrig, Peter and Magenheim, Johannes}, publisher = {Universit{\"a}tsverlag Potsdam}, address = {Potsdam}, isbn = {978-3-86956-313-8}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-74920}, pages = {186}, year = {2015}, abstract = {Die Tagung HDI 2014 in Freiburg zur Hochschuldidaktik der Informatik HDI wurde erneut vom Fachbereich Informatik und Ausbildung / Didaktik der Informatik (IAD) in der Gesellschaft f{\"u}r Informatik e. V. (GI) organisiert. Sie dient den Lehrenden der Informatik in Studieng{\"a}ngen an Hochschulen als Forum der Information und des Austauschs {\"u}ber neue didaktische Ans{\"a}tze und bildungspolitische Themen im Bereich der Hochschulausbildung aus der fachlichen Perspektive der Informatik. Die HDI 2014 ist nun bereits die sechste Ausgabe der HDI. F{\"u}r sie wurde das spezielle Motto „Gestalten und Meistern von {\"U}berg{\"a}ngen" gew{\"a}hlt. Damit soll ein besonderes Augenmerk auf die {\"U}berg{\"a}nge von Schule zum Studium, vom Bachelor zum Master, vom Studium zur Promotion oder vom Studium zur Arbeitswelt gelegt werden.}, language = {de} } @book{Freischlad2009, author = {Freischlad, Stefan}, title = {Entwicklung und Erprobung des Didaktischen Systems Internetworking im Informatikunterricht}, publisher = {Universit{\"a}tsverlag Potsdam}, address = {Potsdam}, isbn = {978-3-86956-058-8}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-41851}, publisher = {Universit{\"a}t Potsdam}, pages = {XIV, 405}, year = {2009}, abstract = {Internetbasierte Informatiksysteme beeinflussen in steigendem Maße Situationen in unterschiedlichen Lebensbereichen. Kompetenzen zur Verwendung von Internetanwendungen und -diensten m{\"u}ssen explizit erworben werden, weil damit ein notwendiger Einblick in nicht beobachtbare Abl{\"a}ufe und nicht offen sichtbare Strukturen verbunden ist. Bisher gibt es Vorschl{\"a}ge f{\"u}r die Gestaltung schulischer Lehr-Lernprozesse zu ausgew{\"a}hlten Teilaspekten des Internets. Es fehlt eine systematische Analyse des Bildungsbedarfs und ein daraus resultierendes Unterrichtsmodell. In dieser Arbeit wird ein Gesamtkonzept f{\"u}r den Informatikunterricht in der Sekundarstufe II vorgestellt, das zu zielgerichteter und verantwortungsvoller Anwendung des Internets beitr{\"a}gt. Die vorliegende Arbeit umfasst den Prozess von der Analyse erforderlicher Kompetenzen bis zur Realisierung von Lehr-Lernprozessen im Informatikunterricht in der Sekundarstufe II. Es werden der Beitrag der Informatik zu identifizierten Kompetenzen untersucht und Bildungsanforderungen bestimmt. Bildungsempfehlungen und Forschungsergebnisse zu erfolgreichen Unterrichtseinheiten werden im Hinblick auf die Bildungsziele analysiert. Der Informatikunterricht unterst{\"u}tzt die Kompetenzentwicklung zu internetbasierten digitalen Medien. Es wird die Entwicklung eines Unterrichtsmodells zu Internetworking beschrieben. Dazu wird der Ansatz der Didaktischen Systeme untersucht, weiter entwickelt und auf den Bereich Internetworking {\"u}bertragen. Der theoretische Ansatz wird dazu in vier Unterrichtsprojekten zu Internetworking in der Praxis realisiert. Beziehungen zwischen Fachkonzepten zu Internetworking werden untersucht und durch Wissensstrukturen zur Planung von Unterrichtsprojekten eingesetzt und in der Praxis erprobt. Die Beschreibung von Lernaktivit{\"a}ten erfolgt auf der Basis von Aufgabenklassen, die das notwendige Wissen zur Bearbeitung einer Aufgabenstellung repr{\"a}sentieren. Auf der Grundlage des Ablaufs der Aufgabenbearbeitung werden Eigenschaften von Aufgaben beschrieben und zu deren Gestaltung nutzbar gemacht. Bisher nicht durchf{\"u}hrbare T{\"a}tigkeiten im Unterricht werden durch die Entwicklung der Lernsoftware Filius erm{\"o}glicht. Die Reduktion der komplexen Wirklichkeit durch Simulation realer internetbasierter Informatiksysteme und die Auswahl geeigneter Sichten auf den Untersuchungsgegenstand werden mit Ergebnissen der Informatikdidaktik begr{\"u}ndet. Unterrichtsprojekte zu den Zielen werden durchgef{\"u}hrt, um Lehr-Lernprozesse zu erkunden und das entwickelte Didaktische System zu erproben. Ausgehend von der theoretischen Fundierung erfolgt die praktische Realisierung von Lehr-Lernprozessen. Zur Erprobung im Informatikunterricht der Sekundarstufe II in Nordrhein-Westfalen werden Minimalziele aufgrund der Lehrvorgaben bestimmt. Die methodische Gestaltung in der Erprobung erfolgt unter Ber{\"u}cksichtigung der Vorgaben f{\"u}r den Informatikunterricht und allgemeinen Anforderungen der Fachdidaktik. Handlungsorientierte Unterrichtsmittel werden ausgew{\"a}hlt und in der Praxis zur Untersuchung der Lehr-Lernprozesse verwendet. Im Unterricht identifizierte Lernschwierigkeiten f{\"u}hren zur Modifikation der Wissensstrukturen und werden im Entwicklungsprozess von Filius ber{\"u}cksichtigt. Die Erkenntnisse aus Unterrichtsprojekten werden genutzt, um zu bestimmen, zu welchen Aufgabenklassen weitere Aufgaben erforderlich sind und inwieweit das aus den identifizierten Merkmalen abgeleitete Vorgehen zur Entwicklung niveaubestimmender Aufgaben genutzt werden kann. Die Erprobungen best{\"a}tigen die Tragf{\"a}higkeit des Didaktischen Systems Internetworking und leisten mit der Implementierung in der Praxis einen Beitrag zur Untersuchung von Kompetenzentwicklung im Informatikunterricht. Mit dem Didaktischen System Internetworking wird ein theoretisch fundiertes und empirisch erprobtes Unterrichtsmodell zur Entwicklung von Kompetenzen zur Einrichtung und Anwendung internetbasierter Informatiksysteme beschrieben.}, language = {de} } @phdthesis{Floeter2005, author = {Fl{\"o}ter, Andr{\´e}}, title = {Analyzing biological expression data based on decision tree induction}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-6416}, school = {Universit{\"a}t Potsdam}, year = {2005}, abstract = {Modern biological analysis techniques supply scientists with various forms of data. One category of such data are the so called "expression data". These data indicate the quantities of biochemical compounds present in tissue samples. Recently, expression data can be generated at a high speed. This leads in turn to amounts of data no longer analysable by classical statistical techniques. Systems biology is the new field that focuses on the modelling of this information. At present, various methods are used for this purpose. One superordinate class of these meth­ods is machine learning. Methods of this kind had, until recently, predominantly been used for classification and prediction tasks. This neglected a powerful secondary benefit: the ability to induce interpretable models. Obtaining such models from data has become a key issue within Systems biology. Numerous approaches have been proposed and intensively discussed. This thesis focuses on the examination and exploitation of one basic technique: decision trees. The concept of comparing sets of decision trees is developed. This method offers the pos­sibility of identifying significant thresholds in continuous or discrete valued attributes through their corresponding set of decision trees. Finding significant thresholds in attributes is a means of identifying states in living organisms. Knowing about states is an invaluable clue to the un­derstanding of dynamic processes in organisms. Applied to metabolite concentration data, the proposed method was able to identify states which were not found with conventional techniques for threshold extraction. A second approach exploits the structure of sets of decision trees for the discovery of com­binatorial dependencies between attributes. Previous work on this issue has focused either on expensive computational methods or the interpretation of single decision trees ­ a very limited exploitation of the data. This has led to incomplete or unstable results. That is why a new method is developed that uses sets of decision trees to overcome these limitations. Both the introduced methods are available as software tools. They can be applied consecu­tively or separately. That way they make up a package of analytical tools that usefully supplement existing methods. By means of these tools, the newly introduced methods were able to confirm existing knowl­edge and to suggest interesting and new relationships between metabolites.}, subject = {Molekulare Bioinformatik}, language = {en} } @phdthesis{Felgentreff2017, author = {Felgentreff, Tim}, title = {The Design and Implementation of Object-Constraint Programming}, school = {Universit{\"a}t Potsdam}, pages = {183}, year = {2017}, language = {en} } @misc{Fandino2019, author = {Fandi{\~n}o, Jorge}, title = {Founded (auto)epistemic equilibrium logic satisfies epistemic splitting}, series = {Postprints der Universit{\"a}t Potsdam : Mathematisch-Naturwissenschaftliche Reihe}, journal = {Postprints der Universit{\"a}t Potsdam : Mathematisch-Naturwissenschaftliche Reihe}, number = {1060}, issn = {1866-8372}, doi = {10.25932/publishup-46968}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-469685}, pages = {671 -- 687}, year = {2019}, abstract = {In a recent line of research, two familiar concepts from logic programming semantics (unfounded sets and splitting) were extrapolated to the case of epistemic logic programs. The property of epistemic splitting provides a natural and modular way to understand programs without epistemic cycles but, surprisingly, was only fulfilled by Gelfond's original semantics (G91), among the many proposals in the literature. On the other hand, G91 may suffer from a kind of self-supported, unfounded derivations when epistemic cycles come into play. Recently, the absence of these derivations was also formalised as a property of epistemic semantics called foundedness. Moreover, a first semantics proved to satisfy foundedness was also proposed, the so-called Founded Autoepistemic Equilibrium Logic (FAEEL). In this paper, we prove that FAEEL also satisfies the epistemic splitting property something that, together with foundedness, was not fulfilled by any other approach up to date. To prove this result, we provide an alternative characterisation of FAEEL as a combination of G91 with a simpler logic we called Founded Epistemic Equilibrium Logic (FEEL), which is somehow an extrapolation of the stable model semantics to the modal logic S5.}, language = {en} } @phdthesis{Dramlitsch2002, author = {Dramlitsch, Thomas}, title = {Distributed computations in a dynamic, heterogeneous Grid environment}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-0000759}, school = {Universit{\"a}t Potsdam}, year = {2002}, abstract = {Die immer dichtere und schnellere Vernetzung von Rechnern und Rechenzentren {\"u}ber Hochgeschwindigkeitsnetzwerke erm{\"o}glicht eine neue Art des wissenschaftlich verteilten Rechnens, bei der geographisch weit auseinanderliegende Rechenkapazit{\"a}ten zu einer Gesamtheit zusammengefasst werden k{\"o}nnen. Dieser so entstehende virtuelle Superrechner, der selbst aus mehreren Grossrechnern besteht, kann dazu genutzt werden Probleme zu berechnen, f{\"u}r die die einzelnen Grossrechner zu klein sind. Die Probleme, die numerisch mit heutigen Rechenkapazit{\"a}ten nicht l{\"o}sbar sind, erstrecken sich durch s{\"a}mtliche Gebiete der heutigen Wissenschaft, angefangen von Astrophysik, Molek{\"u}lphysik, Bioinformatik, Meteorologie, bis hin zur Zahlentheorie und Fluiddynamik um nur einige Gebiete zu nennen. Je nach Art der Problemstellung und des L{\"o}sungsverfahrens gestalten sich solche "Meta-Berechnungen" mehr oder weniger schwierig. Allgemein kann man sagen, dass solche Berechnungen um so schwerer und auch um so uneffizienter werden, je mehr Kommunikation zwischen den einzelnen Prozessen (oder Prozessoren) herrscht. Dies ist dadurch begr{\"u}ndet, dass die Bandbreiten bzw. Latenzzeiten zwischen zwei Prozessoren auf demselben Grossrechner oder Cluster um zwei bis vier Gr{\"o}ssenordnungen h{\"o}her bzw. niedriger liegen als zwischen Prozessoren, welche hunderte von Kilometern entfernt liegen. Dennoch bricht nunmehr eine Zeit an, in der es m{\"o}glich ist Berechnungen auf solch virtuellen Supercomputern auch mit kommunikationsintensiven Programmen durchzuf{\"u}hren. Eine grosse Klasse von kommunikations- und berechnungsintensiven Programmen ist diejenige, die die L{\"o}sung von Differentialgleichungen mithilfe von finiten Differenzen zum Inhalt hat. Gerade diese Klasse von Programmen und deren Betrieb in einem virtuellen Superrechner wird in dieser vorliegenden Dissertation behandelt. Methoden zur effizienteren Durchf{\"u}hrung von solch verteilten Berechnungen werden entwickelt, analysiert und implementiert. Der Schwerpunkt liegt darin vorhandene, klassische Parallelisierungsalgorithmen zu analysieren und so zu erweitern, dass sie vorhandene Informationen (z.B. verf{\"u}gbar durch das Globus Toolkit) {\"u}ber Maschinen und Netzwerke zur effizienteren Parallelisierung nutzen. Soweit wir wissen werden solche Zusatzinformationen kaum in relevanten Programmen genutzt, da der Grossteil aller Parallelisierungsalgorithmen implizit f{\"u}r die Ausf{\"u}hrung auf Grossrechnern oder Clustern entwickelt wurde.}, language = {en} } @phdthesis{Dornhege2006, author = {Dornhege, Guido}, title = {Increasing information transfer rates for brain-computer interfacing}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-7690}, school = {Universit{\"a}t Potsdam}, year = {2006}, abstract = {The goal of a Brain-Computer Interface (BCI) consists of the development of a unidirectional interface between a human and a computer to allow control of a device only via brain signals. While the BCI systems of almost all other groups require the user to be trained over several weeks or even months, the group of Prof. Dr. Klaus-Robert M{\"u}ller in Berlin and Potsdam, which I belong to, was one of the first research groups in this field which used machine learning techniques on a large scale. The adaptivity of the processing system to the individual brain patterns of the subject confers huge advantages for the user. Thus BCI research is considered a hot topic in machine learning and computer science. It requires interdisciplinary cooperation between disparate fields such as neuroscience, since only by combining machine learning and signal processing techniques based on neurophysiological knowledge will the largest progress be made. In this work I particularly deal with my part of this project, which lies mainly in the area of computer science. I have considered the following three main points: Establishing a performance measure based on information theory: I have critically illuminated the assumptions of Shannon's information transfer rate for application in a BCI context. By establishing suitable coding strategies I was able to show that this theoretical measure approximates quite well to what is practically achieveable. Transfer and development of suitable signal processing and machine learning techniques: One substantial component of my work was to develop several machine learning and signal processing algorithms to improve the efficiency of a BCI. Based on the neurophysiological knowledge that several independent EEG features can be observed for some mental states, I have developed a method for combining different and maybe independent features which improved performance. In some cases the performance of the combination algorithm outperforms the best single performance by more than 50 \%. Furthermore, I have theoretically and practically addressed via the development of suitable algorithms the question of the optimal number of classes which should be used for a BCI. It transpired that with BCI performances reported so far, three or four different mental states are optimal. For another extension I have combined ideas from signal processing with those of machine learning since a high gain can be achieved if the temporal filtering, i.e., the choice of frequency bands, is automatically adapted to each subject individually. Implementation of the Berlin brain computer interface and realization of suitable experiments: Finally a further substantial component of my work was to realize an online BCI system which includes the developed methods, but is also flexible enough to allow the simple realization of new algorithms and ideas. So far, bitrates of up to 40 bits per minute have been achieved with this system by absolutely untrained users which, compared to results of other groups, is highly successful.}, subject = {Kybernetik}, language = {en} } @article{DimopoulosGebserLuehneetal.2019, author = {Dimopoulos, Yannis and Gebser, Martin and L{\"u}hne, Patrick and Romero Davila, Javier and Schaub, Torsten}, title = {plasp 3}, series = {Theory and practice of logic programming}, volume = {19}, journal = {Theory and practice of logic programming}, number = {3}, publisher = {Cambridge Univ. Press}, address = {New York}, issn = {1471-0684}, doi = {10.1017/S1471068418000583}, pages = {477 -- 504}, year = {2019}, abstract = {We describe the new version of the Planning Domain Definition Language (PDDL)-to-Answer Set Programming (ASP) translator plasp. First, it widens the range of accepted PDDL features. Second, it contains novel planning encodings, some inspired by Satisfiability Testing (SAT) planning and others exploiting ASP features such as well-foundedness. All of them are designed for handling multivalued fluents in order to capture both PDDL as well as SAS planning formats. Third, enabled by multishot ASP solving, it offers advanced planning algorithms also borrowed from SAT planning. As a result, plasp provides us with an ASP-based framework for studying a variety of planning techniques in a uniform setting. Finally, we demonstrate in an empirical analysis that these techniques have a significant impact on the performance of ASP planning.}, language = {en} } @phdthesis{Dietze2004, author = {Dietze, Stefan}, title = {Modell und Optimierungsansatz f{\"u}r Open Source Softwareentwicklungsprozesse}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-0001594}, school = {Universit{\"a}t Potsdam}, year = {2004}, abstract = {Gerade in den letzten Jahren erfuhr Open Source Software (OSS) eine zunehmende Verbreitung und Popularit{\"a}t und hat sich in verschiedenen Anwendungsdom{\"a}nen etabliert. Die Prozesse, welche sich im Kontext der OSS-Entwicklung (auch: OSSD \– Open Source Software-Development) evolution{\"a}r herausgebildet haben, weisen in den verschiedenen OSS-Entwicklungsprojekten z.T. {\"a}hnliche Eigenschaften und Strukturen auf und auch die involvierten Entit{\"a}ten, 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 {\"u}bertragbaren Modell abstrahiert. Auch in der Wissenschaftsdisziplin des Software Engineering (SE) wurde bereits erkannt, dass sich der OSSD-Ansatz in verschiedenen Aspekten erheblich von klassischen (propriet{\"a}ren) Modellen des SE unterscheidet und daher diese Methoden einer eigenen wissenschaftlichen Betrachtung bed{\"u}rfen. In verschiedenen Publikationen wurden zwar bereits einzelne Aspekte der OSS-Entwicklung analysiert und Theorien {\"u}ber 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 f{\"u}r 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, Prozessentit{\"a}ten und Software-Infrastrukturen der untersuchten OSSD-Projekte. Es basiert auf einem eigens entwickelten Metamodell, welches die zu analysierenden Entit{\"a}ten identifiziert und die Modellierungssichten und -elemente beschreibt, die zur UML-basierten Beschreibung der Entwicklungsprozesse verwendet werden. In einem weiteren Arbeitsschritt wird eine weiterf{\"u}hrende Analyse des identifizierten Modells durchgef{\"u}hrt, um Implikationen, und Optimierungspotentiale aufzuzeigen. Diese umfassen beispielsweise die ungen{\"u}gende Plan- und Terminierbarkeit von Prozessen oder die beobachtete Tendenz von OSSD-Akteuren, verschiedene Aktivit{\"a}ten mit unterschiedlicher Intensit{\"a}t entsprechend der subjektiv wahrgenommenen Anreize auszu{\"u}ben, was zur Vernachl{\"a}ssigung einiger Prozesse f{\"u}hrt. Anschließend werden Optimierungszielstellungen dargestellt, die diese Unzul{\"a}nglichkeiten adressieren, und ein Optimierungsansatz zur Verbesserung des OSSD-Modells wird beschrieben. Dieser Ansatz umfasst die Erweiterung der identifizierten Rollen, die Einf{\"u}hrung 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 Qualit{\"a}tssicherung und der Kompensation von vernachl{\"a}ssigten Prozessen, um sowohl die entwickelte Software- als auch die Prozessqualit{\"a}t im OSSD-Kontext zu verbessern. Desweiteren werden Softwarefunktionalit{\"a}ten beschrieben, welche die identifizierte bestehende Software-Infrastruktur erweitern und eine gesamtheitlichere, softwaretechnische Unterst{\"u}tzung der OSSD-Prozesse erm{\"o}glichen 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 Unterst{\"u}tzung des OSSD-Modells verwendet werden kann.}, language = {de} } @phdthesis{Dick2016, author = {Dick, Uwe}, title = {Discriminative Classification Models for Internet Security}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-102593}, school = {Universit{\"a}t Potsdam}, pages = {x, 57}, year = {2016}, abstract = {Services that operate over the Internet are under constant threat of being exposed to fraudulent use. Maintaining good user experience for legitimate users often requires the classification of entities as malicious or legitimate in order to initiate countermeasures. As an example, inbound email spam filters decide for spam or non-spam. They can base their decision on both the content of each email as well as on features that summarize prior emails received from the sending server. In general, discriminative classification methods learn to distinguish positive from negative entities. Each decision for a label may be based on features of the entity and related entities. When labels of related entities have strong interdependencies---as can be assumed e.g. for emails being delivered by the same user---classification decisions should not be made independently and dependencies should be modeled in the decision function. This thesis addresses the formulation of discriminative classification problems that are tailored for the specific demands of the following three Internet security applications. Theoretical and algorithmic solutions are devised to protect an email service against flooding of user inboxes, to mitigate abusive usage of outbound email servers, and to protect web servers against distributed denial of service attacks. In the application of filtering an inbound email stream for unsolicited emails, utilizing features that go beyond each individual email's content can be valuable. Information about each sending mail server can be aggregated over time and may help in identifying unwanted emails. However, while this information will be available to the deployed email filter, some parts of the training data that are compiled by third party providers may not contain this information. The missing features have to be estimated at training time in order to learn a classification model. In this thesis an algorithm is derived that learns a decision function that integrates over a distribution of values for each missing entry. The distribution of missing values is a free parameter that is optimized to learn an optimal decision function. The outbound stream of emails of an email service provider can be separated by the customer IDs that ask for delivery. All emails that are sent by the same ID in the same period of time are related, both in content and in label. Hijacked customer accounts may send batches of unsolicited emails to other email providers, which in turn might blacklist the sender's email servers after detection of incoming spam emails. The risk of being blocked from further delivery depends on the rate of outgoing unwanted emails and the duration of high spam sending rates. An optimization problem is developed that minimizes the expected cost for the email provider by learning a decision function that assigns a limit on the sending rate to customers based on the each customer's email stream. Identifying attacking IPs during HTTP-level DDoS attacks allows to block those IPs from further accessing the web servers. DDoS attacks are usually carried out by infected clients that are members of the same botnet and show similar traffic patterns. HTTP-level attacks aim at exhausting one or more resources of the web server infrastructure, such as CPU time. If the joint set of attackers cannot increase resource usage close to the maximum capacity, no effect will be experienced by legitimate users of hosted web sites. However, if the additional load raises the computational burden towards the critical range, user experience will degrade until service may be unavailable altogether. As the loss of missing one attacker depends on block decisions for other attackers---if most other attackers are detected, not blocking one client will likely not be harmful---a structured output model has to be learned. In this thesis an algorithm is developed that learns a structured prediction decoder that searches the space of label assignments, guided by a policy. Each model is evaluated on real-world data and is compared to reference methods. The results show that modeling each classification problem according to the specific demands of the task improves performance over solutions that do not consider the constraints inherent to an application.}, language = {en} } @inproceedings{DeselOpelSiegerisetal.2023, author = {Desel, J{\"o}rg and Opel, Simone and Siegeris, Juliane and Draude, Claude and Weber, Gerhard and Schell, Timon and Schwill, Andreas and Thorbr{\"u}gge, Carsten and Sch{\"a}fer, Len Ole and Netzer, Cajus Marian and Gerstenberger, Dietrich and Winkelnkemper, Felix and Schulte, Carsten and B{\"o}ttcher, Axel and Thurner, Veronika and H{\"a}fner, Tanja and Ottinger, Sarah and Große-B{\"o}lting, Gregor and Scheppach, Lukas and M{\"u}hling, Andreas and Baberowski, David and Leonhardt, Thiemo and Rentsch, Susanne and Bergner, Nadine and Bonorden, Leif and Stemme, Jonas and Hoppe, Uwe and Weicker, Karsten and Bender, Esther and Barbas, Helena and Hamann, Fabian and Soll, Marcus and Sitzmann, Daniel}, title = {Hochschuldidaktik Informatik HDI 2021}, series = {Commentarii informaticae didacticae}, booktitle = {Commentarii informaticae didacticae}, number = {13}, editor = {Desel, J{\"o}rg and Opel, Simone and Siegeris, Juliane}, publisher = {Universit{\"a}tsverlag Potsdam}, address = {Potsdam}, isbn = {978-3-86956-548-4}, issn = {1868-0844}, doi = {10.25932/publishup-56507}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-565070}, pages = {299}, year = {2023}, abstract = {Die Fachtagungen HDI (Hochschuldidaktik Informatik) besch{\"a}ftigen sich mit den unterschiedlichen Aspekten informatischer Bildung im Hochschulbereich. Neben den allgemeinen Themen wie verschiedenen Lehr- und Lernformen, dem Einsatz von Informatiksystemen in der Hochschullehre oder Fragen der Gewinnung von geeigneten Studierenden, deren Kompetenzerwerb oder auch der Betreuung der Studierenden widmet sich die HDI immer auch einem Schwerpunktthema. Im Jahr 2021 war dies die Ber{\"u}cksichtigung von Diversit{\"a}t in der Lehre. Diskutiert wurden beispielsweise die Einbeziehung von besonderen fachlichen und {\"u}berfachlichen Kompetenzen Studierender, der Unterst{\"u}tzung von Durchl{\"a}ssigkeit aus nichtakademischen Berufen, aber auch die Gestaltung inklusiver Lehr- und Lernszenarios, Aspekte des Lebenslangen Lernens oder sich an die Diversit{\"a}t von Studierenden adaptierte oder adaptierende Lehrsysteme. Dieser Band enth{\"a}lt ausgew{\"a}hlte Beitr{\"a}ge der 9. Fachtagung 2021, die in besonderer Weise die Konferenz und die dort diskutierten Themen repr{\"a}sentieren.}, language = {de} } @inproceedings{DennertMoellerGarmannKujathetal.2016, author = {Dennert-M{\"o}ller, Elisabeth and Garmann, Robert and Kujath, Bertold and Zscheyge, Oliver and Weicker, Karsten and B{\"o}hne, Sebastian and Knobelsdorf, Maria and Kreitz, Christoph and Steen, Alexander and Wisniewski, Max and Benzm{\"u}ller, Christoph and Gebhardt, Kai and Ehlenz, Matthias and Bergner, Nadine and Schroeder, Ulrik}, title = {Hochschuldidaktik der Informatik}, editor = {Schwill, Andreas and Lucke, Ulrike}, publisher = {Universit{\"a}tsverlag Potsdam}, address = {Potsdam}, isbn = {978-3-86956-376-3}, issn = {1868-0844}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-93511}, pages = {102}, year = {2016}, abstract = {Die 7. Fachtagung f{\"u}r Hochschuldidaktik, die 2016 erneut mit der DeLFI E-Learning Fachtagung Informatik stattfand, setzte das erfolgreiche Modell einer Tagung fort, die sich mit hochschuldidaktischen Fragen und der Gestaltung von Studieng{\"a}ngen der Informatik besch{\"a}ftigt. Thema der Tagung waren alle Fragen, die sich der Vermittlung von Informatikgegenst{\"a}nden im Hochschulbereich widmen. Dazu geh{\"o}rten u.a.: • fachdidaktische Konzepte der Vermittlung einzelner Informatikgegenst{\"a}nde • methodische L{\"o}sungen, wie spezielle Lehr- und Lernformen, Durchf{\"u}hrungskonzepte • empirische Ergebnisse und Vergleichsstudien • E-Learning-Ans{\"a}tze, wenn sie ein erkennbares didaktisches Konzept verfolgen • Studienkonzepte und Curricula, organisatorische Fragen, wie Gewinnung von Studierenden, Studieneingangsphase, Abbrecher. Die Fachtagung widmete sich ausgew{\"a}hlten Fragestellungen dieses Themenkomplexes, die durch Vortr{\"a}ge ausgewiesener Experten, durch eingereichte Beitr{\"a}ge und durch Pr{\"a}sentationen und Poster intensiv behandelt wurden. Unser besonderer Dank gilt dem Programmkomitee und den hier nicht genannten Helfern f{\"u}r ihren Einsatz bei der Vorbereitung und Durchf{\"u}hrung der Tagung.}, language = {de} } @phdthesis{Decker2009, author = {Decker, Gero}, title = {Design and analysis of process choreographies}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-40761}, school = {Universit{\"a}t Potsdam}, year = {2009}, abstract = {With the rise of electronic integration between organizations, the need for a precise specification of interaction behavior increases. Information systems, replacing interaction previously carried out by humans via phone, faxes and emails, require a precise specification for handling all possible situations. Such interaction behavior is described in process choreographies. Choreographies enumerate the roles involved, the allowed interactions, the message contents and the behavioral dependencies between interactions. Choreographies serve as interaction contract and are the starting point for adapting existing business processes and systems or for implementing new software components. As a thorough analysis and comparison of choreography modeling languages is missing in the literature, this thesis introduces a requirements framework for choreography languages and uses it for comparing current choreography languages. Language proposals for overcoming the limitations are given for choreography modeling on the conceptual and on the technical level. Using an interconnection modeling style, behavioral dependencies are defined on a per-role basis and different roles are interconnected using message flow. This thesis reveals a number of modeling "anti-patterns" for interconnection modeling, motivating further investigations on choreography languages following the interaction modeling style. Here, interactions are seen as atomic building blocks and the behavioral dependencies between them are defined globally. Two novel language proposals are put forward for this modeling style which have already influenced industrial standardization initiatives. While avoiding many of the pitfalls of interconnection modeling, new anomalies can arise in interaction models. A choreography might not be realizable, i.e. there does not exist a set of interacting roles that collectively realize the specified behavior. This thesis investigates different dimensions of realizability.}, language = {en} } @inproceedings{CurzonKalasSchubertetal.2015, author = {Curzon, Paul and Kalas, Ivan and Schubert, Sigrid and Schaper, Niclas and Barnes, Jan and Kennewell, Steve and Br{\"o}ker, Kathrin and Kastens, Uwe and Magenheim, Johannes and Dagiene, Valentina and Stupuriene, Gabriele and Ellis, Jason Brent and Abreu-Ellis, Carla Reis and Grillenberger, Andreas and Romeike, Ralf and Haugsbakken, Halvdan and Jones, Anthony and Lewin, Cathy and McNicol, Sarah and Nelles, Wolfgang and Neugebauer, Jonas and Ohrndorf, Laura and Schaper, Niclas and Schubert, Sigrid and Opel, Simone and Kramer, Matthias and Trommen, Michael and Pottb{\"a}cker, Florian and Ilaghef, Youssef and Passig, David and Tzuriel, David and Kedmi, Ganit Eshel and Saito, Toshinori and Webb, Mary and Weigend, Michael and Bottino, Rosa and Chioccariello, Augusto and Christensen, Rhonda and Knezek, Gerald and Gioko, Anthony Maina and Angondi, Enos Kiforo and Waga, Rosemary and Ohrndorf, Laura and Or-Bach, Rachel and Preston, Christina and Younie, Sarah and Przybylla, Mareen and Romeike, Ralf and Reynolds, Nicholas and Swainston, Andrew and Bendrups, Faye and Sysło, Maciej M. and Kwiatkowska, Anna Beata and Zieris, Holger and Gerstberger, Herbert and M{\"u}ller, Wolfgang and B{\"u}chner, Steffen and Opel, Simone and Schiller, Thomas and Wegner, Christian and Zender, Raphael and Lucke, Ulrike and Diethelm, Ira and Syrbe, J{\"o}rn and Lai, Kwok-Wing and Davis, Niki and Eickelmann, Birgit and Erstad, Ola and Fisser, Petra and Gibson, David and Khaddage, Ferial and Knezek, Gerald and Micheuz, Peter and Kloos, Carlos Delgado}, title = {KEYCIT 2014}, editor = {Brinda, Torsten and Reynolds, Nicholas and Romeike, Ralf and Schwill, Andreas}, publisher = {Universit{\"a}tsverlag Potsdam}, address = {Potsdam}, isbn = {978-3-86956-292-6}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-70325}, pages = {438}, year = {2015}, abstract = {In our rapidly changing world it is increasingly important not only to be an expert in a chosen field of study but also to be able to respond to developments, master new approaches to solving problems, and fulfil changing requirements in the modern world and in the job market. In response to these needs key competencies in understanding, developing and using new digital technologies are being brought into focus in school and university programmes. The IFIP TC3 conference "KEYCIT - Key Competences in Informatics and ICT (KEYCIT 2014)" was held at the University of Potsdam in Germany from July 1st to 4th, 2014 and addressed the combination of key competencies, Informatics and ICT in detail. The conference was organized into strands focusing on secondary education, university education and teacher education (organized by IFIP WGs 3.1 and 3.3) and provided a forum to present and to discuss research, case studies, positions, and national perspectives in this field.}, language = {en} } @article{ChenLangeAndjelkovicetal.2022, author = {Chen, Junchao and Lange, Thomas and Andjelkovic, Marko and Simevski, Aleksandar and Lu, Li and Krstić, Miloš}, title = {Solar particle event and single event upset prediction from SRAM-based monitor and supervised machine learning}, series = {IEEE transactions on emerging topics in computing / IEEE Computer Society, Institute of Electrical and Electronics Engineers}, volume = {10}, journal = {IEEE transactions on emerging topics in computing / IEEE Computer Society, Institute of Electrical and Electronics Engineers}, number = {2}, publisher = {Institute of Electrical and Electronics Engineers}, address = {[New York, NY]}, issn = {2168-6750}, doi = {10.1109/TETC.2022.3147376}, pages = {564 -- 580}, year = {2022}, abstract = {The intensity of cosmic radiation may differ over five orders of magnitude within a few hours or days during the Solar Particle Events (SPEs), thus increasing for several orders of magnitude the probability of Single Event Upsets (SEUs) in space-borne electronic systems. Therefore, it is vital to enable the early detection of the SEU rate changes in order to ensure timely activation of dynamic radiation hardening measures. In this paper, an embedded approach for the prediction of SPEs and SRAM SEU rate is presented. The proposed solution combines the real-time SRAM-based SEU monitor, the offline-trained machine learning model and online learning algorithm for the prediction. With respect to the state-of-the-art, our solution brings the following benefits: (1) Use of existing on-chip data storage SRAM as a particle detector, thus minimizing the hardware and power overhead, (2) Prediction of SRAM SEU rate one hour in advance, with the fine-grained hourly tracking of SEU variations during SPEs as well as under normal conditions, (3) Online optimization of the prediction model for enhancing the prediction accuracy during run-time, (4) Negligible cost of hardware accelerator design for the implementation of selected machine learning model and online learning algorithm. The proposed design is intended for a highly dependable and self-adaptive multiprocessing system employed in space applications, allowing to trigger the radiation mitigation mechanisms before the onset of high radiation levels.}, language = {en} } @article{CabalarFandinoFarinasdelCerro2021, author = {Cabalar, Pedro and Fandi{\~n}o, Jorge and Fari{\~n}as del Cerro, Luis}, title = {Splitting epistemic logic programs}, series = {Theory and practice of logic programming / publ. for the Association for Logic Programming}, volume = {21}, journal = {Theory and practice of logic programming / publ. for the Association for Logic Programming}, number = {3}, publisher = {Cambridge Univ. Press}, address = {Cambridge [u.a.]}, issn = {1471-0684}, doi = {10.1017/S1471068420000058}, pages = {296 -- 316}, year = {2021}, abstract = {Epistemic logic programs constitute an extension of the stable model semantics to deal with new constructs called subjective literals. Informally speaking, a subjective literal allows checking whether some objective literal is true in all or some stable models. As it can be imagined, the associated semantics has proved to be non-trivial, since the truth of subjective literals may interfere with the set of stable models it is supposed to query. As a consequence, no clear agreement has been reached and different semantic proposals have been made in the literature. Unfortunately, comparison among these proposals has been limited to a study of their effect on individual examples, rather than identifying general properties to be checked. In this paper, we propose an extension of the well-known splitting property for logic programs to the epistemic case. We formally define when an arbitrary semantics satisfies the epistemic splitting property and examine some of the consequences that can be derived from that, including its relation to conformant planning and to epistemic constraints. Interestingly, we prove (through counterexamples) that most of the existing approaches fail to fulfill the epistemic splitting property, except the original semantics proposed by Gelfond 1991 and a recent proposal by the authors, called Founded Autoepistemic Equilibrium Logic.}, language = {en} } @phdthesis{Boeken2022, author = {B{\"o}ken, Bj{\"o}rn}, title = {Improving prediction accuracy using dynamic information}, doi = {10.25932/publishup-58512}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-585125}, school = {Universit{\"a}t Potsdam}, pages = {xii, 160}, year = {2022}, abstract = {Accurately solving classification problems nowadays is likely to be the most relevant machine learning task. Binary classification separating two classes only is algorithmically simpler but has fewer potential applications as many real-world problems are multi-class. On the reverse, separating only a subset of classes simplifies the classification task. Even though existing multi-class machine learning algorithms are very flexible regarding the number of classes, they assume that the target set Y is fixed and cannot be restricted once the training is finished. On the other hand, existing state-of-the-art production environments are becoming increasingly interconnected with the advance of Industry 4.0 and related technologies such that additional information can simplify the respective classification problems. In light of this, the main aim of this thesis is to introduce dynamic classification that generalizes multi-class classification such that the target class set can be restricted arbitrarily to a non-empty class subset M of Y at any time between two consecutive predictions. This task is solved by a combination of two algorithmic approaches. First, classifier calibration, which transforms predictions into posterior probability estimates that are intended to be well calibrated. The analysis provided focuses on monotonic calibration and in particular corrects wrong statements that appeared in the literature. It also reveals that bin-based evaluation metrics, which became popular in recent years, are unjustified and should not be used at all. Next, the validity of Platt scaling, which is the most relevant parametric calibration approach, is analyzed in depth. In particular, its optimality for classifier predictions distributed according to four different families of probability distributions as well its equivalence with Beta calibration up to a sigmoidal preprocessing are proven. For non-monotonic calibration, extended variants on kernel density estimation and the ensemble method EKDE are introduced. Finally, the calibration techniques are evaluated using a simulation study with complete information as well as on a selection of 46 real-world data sets. Building on this, classifier calibration is applied as part of decomposition-based classification that aims to reduce multi-class problems to simpler (usually binary) prediction tasks. For the involved fusing step performed at prediction time, a new approach based on evidence theory is presented that uses classifier calibration to model mass functions. This allows the analysis of decomposition-based classification against a strictly formal background and to prove closed-form equations for the overall combinations. Furthermore, the same formalism leads to a consistent integration of dynamic class information, yielding a theoretically justified and computationally tractable dynamic classification model. The insights gained from this modeling are combined with pairwise coupling, which is one of the most relevant reduction-based classification approaches, such that all individual predictions are combined with a weight. This not only generalizes existing works on pairwise coupling but also enables the integration of dynamic class information. Lastly, a thorough empirical study is performed that compares all newly introduced approaches to existing state-of-the-art techniques. For this, evaluation metrics for dynamic classification are introduced that depend on corresponding sampling strategies. Thereafter, these are applied during a three-part evaluation. First, support vector machines and random forests are applied on 26 data sets from the UCI Machine Learning Repository. Second, two state-of-the-art deep neural networks are evaluated on five benchmark data sets from a relatively recent reference work. Here, computationally feasible strategies to apply the presented algorithms in combination with large-scale models are particularly relevant because a naive application is computationally intractable. Finally, reference data from a real-world process allowing the inclusion of dynamic class information are collected and evaluated. The results show that in combination with support vector machines and random forests, pairwise coupling approaches yield the best results, while in combination with deep neural networks, differences between the different approaches are mostly small to negligible. Most importantly, all results empirically confirm that dynamic classification succeeds in improving the respective prediction accuracies. Therefore, it is crucial to pass dynamic class information in respective applications, which requires an appropriate digital infrastructure.}, language = {en} } @article{BoehneKreitzKnobelsdorf2016, author = {B{\"o}hne, Sebastian and Kreitz, Christoph and Knobelsdorf, Maria}, title = {Mathematisches Argumentieren und Beweisen mit dem Theorembeweiser Coq}, series = {Commentarii informaticae didacticae (CID)}, journal = {Commentarii informaticae didacticae (CID)}, number = {10}, publisher = {Universit{\"a}tsverlag Potsdam}, address = {Potsdam}, isbn = {978-3-86956-376-3}, issn = {1868-0844}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-94824}, pages = {69 -- 80}, year = {2016}, abstract = {Informatik-Studierende haben in der Mehrzahl Schwierigkeiten, einen Einstieg in die Theoretische Informatik zu finden und die Leistungsanforderungen in den Endklausuren der zugeh{\"o}rigen Lehrveranstaltungen zu erf{\"u}llen. Wir argumentieren, dass dieser Symptomatik mangelnde Kompetenzen im Umgang mit abstrakten und stark formalisierten Themeninhalten zugrunde liegen und schlagen vor, einen Beweisassistenten als interaktives Lernwerkzeug in der Eingangslehre der Theoretischen Informatik zu nutzen, um entsprechende Kompetenzen zu st{\"a}rken.}, language = {de} } @phdthesis{Boehm2013, author = {B{\"o}hm, Christoph}, title = {Enriching the Web of Data with topics and links}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-68624}, school = {Universit{\"a}t Potsdam}, year = {2013}, abstract = {This thesis presents novel ideas and research findings for the Web of Data - a global data space spanning many so-called Linked Open Data sources. Linked Open Data adheres to a set of simple principles to allow easy access and reuse for data published on the Web. Linked Open Data is by now an established concept and many (mostly academic) publishers adopted the principles building a powerful web of structured knowledge available to everybody. However, so far, Linked Open Data does not yet play a significant role among common web technologies that currently facilitate a high-standard Web experience. In this work, we thoroughly discuss the state-of-the-art for Linked Open Data and highlight several shortcomings - some of them we tackle in the main part of this work. First, we propose a novel type of data source meta-information, namely the topics of a dataset. This information could be published with dataset descriptions and support a variety of use cases, such as data source exploration and selection. For the topic retrieval, we present an approach coined Annotated Pattern Percolation (APP), which we evaluate with respect to topics extracted from Wikipedia portals. Second, we contribute to entity linking research by presenting an optimization model for joint entity linking, showing its hardness, and proposing three heuristics implemented in the LINked Data Alignment (LINDA) system. Our first solution can exploit multi-core machines, whereas the second and third approach are designed to run in a distributed shared-nothing environment. We discuss and evaluate the properties of our approaches leading to recommendations which algorithm to use in a specific scenario. The distributed algorithms are among the first of their kind, i.e., approaches for joint entity linking in a distributed fashion. Also, we illustrate that we can tackle the entity linking problem on the very large scale with data comprising more than 100 millions of entity representations from very many sources. Finally, we approach a sub-problem of entity linking, namely the alignment of concepts. We again target a method that looks at the data in its entirety and does not neglect existing relations. Also, this concept alignment method shall execute very fast to serve as a preprocessing for further computations. Our approach, called Holistic Concept Matching (HCM), achieves the required speed through grouping the input by comparing so-called knowledge representations. Within the groups, we perform complex similarity computations, relation conclusions, and detect semantic contradictions. The quality of our result is again evaluated on a large and heterogeneous dataset from the real Web. In summary, this work contributes a set of techniques for enhancing the current state of the Web of Data. All approaches have been tested on large and heterogeneous real-world input.}, language = {en} } @misc{Baermann2006, type = {Master Thesis}, author = {B{\"a}rmann, Daniel}, title = {Aufz{\"a}hlen von DNA-Codes}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-10264}, school = {Universit{\"a}t Potsdam}, year = {2006}, abstract = {In dieser Arbeit wird ein Modell zum Aufz{\"a}hlen von DNA-Codes entwickelt. Indem eine Ordnung auf der Menge aller DNA-Codew{\"o}rter eingef{\"u}hrt und auf die Menge aller Codes erweitert wird, erlaubt das Modell das Auffinden von DNA-Codes mit bestimmten Eigenschaften, wie {\"U}berlappungsfreiheit, Konformit{\"a}t, Kommafreiheit, Stickyfreiheit, {\"U}berhangfreiheit, Teilwortkonformit{\"a}t und anderer bez{\"u}glich einer gegebenen Involution auf der Menge der Codew{\"o}rter. Ein auf Grundlage des geschaffenen Modells entstandenes Werkzeug erlaubt das Suchen von Codes mit beliebigen Kombinationen von Codeeigenschaften. Ein weiterer wesentlicher Bestandteil dieser Arbeit ist die Untersuchung der Optimalit{\"a}t von DNA-Codes bez{\"u}glich ihrer Informationsrate sowie das Finden solider DNA-Codes.}, subject = {DNS}, language = {de} } @phdthesis{Buchholz2006, author = {Buchholz, Henrik}, title = {Real-time visualization of 3D city models}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-13337}, school = {Universit{\"a}t Potsdam}, year = {2006}, abstract = {An increasing number of applications requires user interfaces that facilitate the handling of large geodata sets. Using virtual 3D city models, complex geospatial information can be communicated visually in an intuitive way. Therefore, real-time visualization of virtual 3D city models represents a key functionality for interactive exploration, presentation, analysis, and manipulation of geospatial data. This thesis concentrates on the development and implementation of concepts and techniques for real-time city model visualization. It discusses rendering algorithms as well as complementary modeling concepts and interaction techniques. Particularly, the work introduces a new real-time rendering technique to handle city models of high complexity concerning texture size and number of textures. Such models are difficult to handle by current technology, primarily due to two problems: - Limited texture memory: The amount of simultaneously usable texture data is limited by the memory of the graphics hardware. - Limited number of textures: Using several thousand different textures simultaneously causes significant performance problems due to texture switch operations during rendering. The multiresolution texture atlases approach, introduced in this thesis, overcomes both problems. During rendering, it permanently maintains a small set of textures that are sufficient for the current view and the screen resolution available. The efficiency of multiresolution texture atlases is evaluated in performance tests. To summarize, the results demonstrate that the following goals have been achieved: - Real-time rendering becomes possible for 3D scenes whose amount of texture data exceeds the main memory capacity. - Overhead due to texture switches is kept permanently low, so that the number of different textures has no significant effect on the rendering frame rate. Furthermore, this thesis introduces two new approaches for real-time city model visualization that use textures as core visualization elements: - An approach for visualization of thematic information. - An approach for illustrative visualization of 3D city models. Both techniques demonstrate that multiresolution texture atlases provide a basic functionality for the development of new applications and systems in the domain of city model visualization.}, language = {en} } @phdthesis{Brueckner2012, author = {Br{\"u}ckner, Michael}, title = {Prediction games : machine learning in the presence of an adversary}, publisher = {Universit{\"a}tsverlag Potsdam}, address = {Potsdam}, isbn = {978-3-86956-203-2}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-60375}, school = {Universit{\"a}t Potsdam}, pages = {x, 121}, year = {2012}, abstract = {In many applications one is faced with the problem of inferring some functional relation between input and output variables from given data. Consider, for instance, the task of email spam filtering where one seeks to find a model which automatically assigns new, previously unseen emails to class spam or non-spam. Building such a predictive model based on observed training inputs (e.g., emails) with corresponding outputs (e.g., spam labels) is a major goal of machine learning. Many learning methods assume that these training data are governed by the same distribution as the test data which the predictive model will be exposed to at application time. That assumption is violated when the test data are generated in response to the presence of a predictive model. This becomes apparent, for instance, in the above example of email spam filtering. Here, email service providers employ spam filters and spam senders engineer campaign templates such as to achieve a high rate of successful deliveries despite any filters. Most of the existing work casts such situations as learning robust models which are unsusceptible against small changes of the data generation process. The models are constructed under the worst-case assumption that these changes are performed such to produce the highest possible adverse effect on the performance of the predictive model. However, this approach is not capable to realistically model the true dependency between the model-building process and the process of generating future data. We therefore establish the concept of prediction games: We model the interaction between a learner, who builds the predictive model, and a data generator, who controls the process of data generation, as an one-shot game. The game-theoretic framework enables us to explicitly model the players' interests, their possible actions, their level of knowledge about each other, and the order at which they decide for an action. We model the players' interests as minimizing their own cost function which both depend on both players' actions. The learner's action is to choose the model parameters and the data generator's action is to perturbate the training data which reflects the modification of the data generation process with respect to the past data. We extensively study three instances of prediction games which differ regarding the order in which the players decide for their action. We first assume that both player choose their actions simultaneously, that is, without the knowledge of their opponent's decision. We identify conditions under which this Nash prediction game has a meaningful solution, that is, a unique Nash equilibrium, and derive algorithms that find the equilibrial prediction model. As a second case, we consider a data generator who is potentially fully informed about the move of the learner. This setting establishes a Stackelberg competition. We derive a relaxed optimization criterion to determine the solution of this game and show that this Stackelberg prediction game generalizes existing prediction models. Finally, we study the setting where the learner observes the data generator's action, that is, the (unlabeled) test data, before building the predictive model. As the test data and the training data may be governed by differing probability distributions, this scenario reduces to learning under covariate shift. We derive a new integrated as well as a two-stage method to account for this data set shift. In case studies on email spam filtering we empirically explore properties of all derived models as well as several existing baseline methods. We show that spam filters resulting from the Nash prediction game as well as the Stackelberg prediction game in the majority of cases outperform other existing baseline methods.}, language = {en} } @article{Broeker2015, author = {Br{\"o}ker, Kathrin}, title = {Unterst{\"u}tzung Informatik-Studierender durch ein Lernzentrum}, series = {HDI 2014 : Gestalten von {\"U}berg{\"a}ngen}, volume = {2015}, journal = {HDI 2014 : Gestalten von {\"U}berg{\"a}ngen}, number = {9}, editor = {Schubert, Sigrid and Schwill, Andreas}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-84754}, pages = {189 -- 197}, year = {2015}, abstract = {In diesem Papier wird das Konzept eines Lernzentrums f{\"u}r die Informatik (LZI) an der Universit{\"a}t Paderborn vorgestellt. Ausgehend von den fachspezifischen Schwierigkeiten der Informatik Studierenden werden die Angebote des LZIs erl{\"a}utert, die sich {\"u}ber die vier Bereiche Individuelle Beratung und Betreuung, „Offener Lernraum", Workshops und Lehrveranstaltungen sowie Forschung erstrecken. Eine erste Evaluation mittels Feedbackb{\"o}gen zeigt, dass das Angebot bei den Studierenden positiv aufgenommen wird. Zuk{\"u}nftig soll das Angebot des LZIs weiter ausgebaut und verbessert werden. Ausgangsbasis dazu sind weitere Studien.}, language = {de} } @misc{BrewkaSchaubWoltran2018, author = {Brewka, Gerhard and Schaub, Torsten and Woltran, Stefan}, title = {Interview with Gerhard Brewka}, series = {K{\"u}nstliche Intelligenz}, volume = {32}, journal = {K{\"u}nstliche Intelligenz}, number = {2-3}, publisher = {Springer}, address = {Heidelberg}, issn = {0933-1875}, doi = {10.1007/s13218-018-0549-5}, pages = {219 -- 221}, year = {2018}, abstract = {This interview with Gerhard Brewka was conducted by correspondance in May 2018. The question set was compiled by Torsten Schaub and Stefan Woltran.}, language = {en} } @article{BrewkaEllmauthalerKernIsberneretal.2018, author = {Brewka, Gerhard and Ellmauthaler, Stefan and Kern-Isberner, Gabriele and Obermeier, Philipp and Ostrowski, Max and Romero, Javier and Schaub, Torsten and Schieweck, Steffen}, title = {Advanced solving technology for dynamic and reactive applications}, series = {K{\"u}nstliche Intelligenz}, volume = {32}, journal = {K{\"u}nstliche Intelligenz}, number = {2-3}, publisher = {Springer}, address = {Heidelberg}, issn = {0933-1875}, doi = {10.1007/s13218-018-0538-8}, pages = {199 -- 200}, year = {2018}, language = {en} } @article{BredeBotta2021, author = {Brede, Nuria and Botta, Nicola}, title = {On the correctness of monadic backward induction}, series = {Journal of functional programming}, volume = {31}, journal = {Journal of functional programming}, publisher = {Cambridge University Press}, address = {Cambridge}, issn = {1469-7653}, doi = {10.1017/S0956796821000228}, pages = {39}, year = {2021}, abstract = {In control theory, to solve a finite-horizon sequential decision problem (SDP) commonly means to find a list of decision rules that result in an optimal expected total reward (or cost) when taking a given number of decision steps. SDPs are routinely solved using Bellman's backward induction. Textbook authors (e.g. Bertsekas or Puterman) typically give more or less formal proofs to show that the backward induction algorithm is correct as solution method for deterministic and stochastic SDPs. Botta, Jansson and Ionescu propose a generic framework for finite horizon, monadic SDPs together with a monadic version of backward induction for solving such SDPs. In monadic SDPs, the monad captures a generic notion of uncertainty, while a generic measure function aggregates rewards. In the present paper, we define a notion of correctness for monadic SDPs and identify three conditions that allow us to prove a correctness result for monadic backward induction that is comparable to textbook correctness proofs for ordinary backward induction. The conditions that we impose are fairly general and can be cast in category-theoretical terms using the notion of Eilenberg-Moore algebra. They hold in familiar settings like those of deterministic or stochastic SDPs, but we also give examples in which they fail. Our results show that backward induction can safely be employed for a broader class of SDPs than usually treated in textbooks. However, they also rule out certain instances that were considered admissible in the context of Botta et al. 's generic framework. Our development is formalised in Idris as an extension of the Botta et al. framework and the sources are available as supplementary material.}, language = {en} } @phdthesis{Brauer2010, author = {Brauer, Falk}, title = {Extraktion und Identifikation von Entit{\"a}ten in Textdaten im Umfeld der Enterprise Search}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-51409}, school = {Universit{\"a}t Potsdam}, year = {2010}, abstract = {Die automatische Informationsextraktion (IE) aus unstrukturierten Texten erm{\"o}glicht v{\"o}llig neue Wege, auf relevante Informationen zuzugreifen und deren Inhalte zu analysieren, die weit {\"u}ber bisherige Verfahren zur Stichwort-basierten Dokumentsuche hinausgehen. Die Entwicklung von Programmen zur Extraktion von maschinenlesbaren Daten aus Texten erfordert jedoch nach wie vor die Entwicklung von dom{\"a}nenspezifischen Extraktionsprogrammen. Insbesondere im Bereich der Enterprise Search (der Informationssuche im Unternehmensumfeld), in dem eine große Menge von heterogenen Dokumenttypen existiert, ist es oft notwendig ad-hoc Programm-module zur Extraktion von gesch{\"a}ftsrelevanten Entit{\"a}ten zu entwickeln, die mit generischen Modulen in monolithischen IE-Systemen kombiniert werden. Dieser Umstand ist insbesondere kritisch, da potentiell f{\"u}r jeden einzelnen Anwendungsfall ein von Grund auf neues IE-System entwickelt werden muss. Die vorliegende Dissertation untersucht die effiziente Entwicklung und Ausf{\"u}hrung von IE-Systemen im Kontext der Enterprise Search und effektive Methoden zur Ausnutzung bekannter strukturierter Daten im Unternehmenskontext f{\"u}r die Extraktion und Identifikation von gesch{\"a}ftsrelevanten Entit{\"a}ten in Doku-menten. Grundlage der Arbeit ist eine neuartige Plattform zur Komposition von IE-Systemen auf Basis der Beschreibung des Datenflusses zwischen generischen und anwendungsspezifischen IE-Modulen. Die Plattform unterst{\"u}tzt insbesondere die Entwicklung und Wiederverwendung von generischen IE-Modulen und zeichnet sich durch eine h{\"o}here Flexibilit{\"a}t und Ausdrucksm{\"a}chtigkeit im Vergleich zu vorherigen Methoden aus. Ein in der Dissertation entwickeltes Verfahren zur Dokumentverarbeitung interpretiert den Daten-austausch zwischen IE-Modulen als Datenstr{\"o}me und erm{\"o}glicht damit eine weitgehende Parallelisierung von einzelnen Modulen. Die autonome Ausf{\"u}hrung der Module f{\"u}hrt zu einer wesentlichen Beschleu-nigung der Verarbeitung von Einzeldokumenten und verbesserten Antwortzeiten, z. B. f{\"u}r Extraktions-dienste. Bisherige Ans{\"a}tze untersuchen lediglich die Steigerung des durchschnittlichen Dokumenten-durchsatzes durch verteilte Ausf{\"u}hrung von Instanzen eines IE-Systems. Die Informationsextraktion im Kontext der Enterprise Search unterscheidet sich z. B. von der Extraktion aus dem World Wide Web dadurch, dass in der Regel strukturierte Referenzdaten z. B. in Form von Unternehmensdatenbanken oder Terminologien zur Verf{\"u}gung stehen, die oft auch die Beziehungen von Entit{\"a}ten beschreiben. Entit{\"a}ten im Unternehmensumfeld haben weiterhin bestimmte Charakteristiken: Eine Klasse von relevanten Entit{\"a}ten folgt bestimmten Bildungsvorschriften, die nicht immer bekannt sind, auf die aber mit Hilfe von bekannten Beispielentit{\"a}ten geschlossen werden kann, so dass unbekannte Entit{\"a}ten extrahiert werden k{\"o}nnen. Die Bezeichner der anderen Klasse von Entit{\"a}ten haben eher umschreibenden Charakter. Die korrespondierenden Umschreibungen in Texten k{\"o}nnen variieren, wodurch eine Identifikation derartiger Entit{\"a}ten oft erschwert wird. Zur effizienteren Entwicklung von IE-Systemen wird in der Dissertation ein Verfahren untersucht, das alleine anhand von Beispielentit{\"a}ten effektive Regul{\"a}re Ausdr{\"u}cke zur Extraktion von unbekannten Entit{\"a}ten erlernt und damit den manuellen Aufwand in derartigen Anwendungsf{\"a}llen minimiert. Verschiedene Generalisierungs- und Spezialisierungsheuristiken erkennen Muster auf verschiedenen Abstraktionsebenen und schaffen dadurch einen Ausgleich zwischen Genauigkeit und Vollst{\"a}ndigkeit bei der Extraktion. Bekannte Regellernverfahren im Bereich der Informationsextraktion unterst{\"u}tzen die beschriebenen Problemstellungen nicht, sondern ben{\"o}tigen einen (annotierten) Dokumentenkorpus. Eine Methode zur Identifikation von Entit{\"a}ten, die durch Graph-strukturierte Referenzdaten vordefiniert sind, wird als dritter Schwerpunkt untersucht. Es werden Verfahren konzipiert, welche {\"u}ber einen exakten Zeichenkettenvergleich zwischen Text und Referenzdatensatz hinausgehen und Teil{\"u}bereinstimmungen und Beziehungen zwischen Entit{\"a}ten zur Identifikation und Disambiguierung heranziehen. Das in der Arbeit vorgestellte Verfahren ist bisherigen Ans{\"a}tzen hinsichtlich der Genauigkeit und Vollst{\"a}ndigkeit bei der Identifikation {\"u}berlegen.}, language = {de} } @article{BordihnVaszil2020, author = {Bordihn, Henning and Vaszil, Gy{\"o}rgy}, title = {Deterministic Lindenmayer systems with dynamic control of parallelism}, series = {International journal of foundations of computer science}, volume = {31}, journal = {International journal of foundations of computer science}, number = {1}, publisher = {World Scientific}, address = {Singapore}, issn = {0129-0541}, doi = {10.1142/S0129054120400031}, pages = {37 -- 51}, year = {2020}, abstract = {M-rate 0L systems are interactionless Lindenmayer systems together with a function assigning to every string a set of multisets of productions that may be applied simultaneously to the string. Some questions that have been left open in the forerunner papers are examined, and the computational power of deterministic M-rate 0L systems is investigated, where also tabled and extended variants are taken into consideration.}, language = {en} } @article{BordihnVaszil2021, author = {Bordihn, Henning and Vaszil, Gy{\"o}rgy}, title = {Reversible parallel communicating finite automata systems}, series = {Acta informatica}, volume = {58}, journal = {Acta informatica}, number = {4}, publisher = {Springer}, address = {Berlin ; Heidelberg ; New York, NY}, issn = {0001-5903}, doi = {10.1007/s00236-021-00396-9}, pages = {263 -- 279}, year = {2021}, abstract = {We study the concept of reversibility in connection with parallel communicating systems of finite automata (PCFA in short). We define the notion of reversibility in the case of PCFA (also covering the non-deterministic case) and discuss the relationship of the reversibility of the systems and the reversibility of its components. We show that a system can be reversible with non-reversible components, and the other way around, the reversibility of the components does not necessarily imply the reversibility of the system as a whole. We also investigate the computational power of deterministic centralized reversible PCFA. We show that these very simple types of PCFA (returning or non-returning) can recognize regular languages which cannot be accepted by reversible (deterministic) finite automata, and that they can even accept languages that are not context-free. We also separate the deterministic and non-deterministic variants in the case of systems with non-returning communication. We show that there are languages accepted by non-deterministic centralized PCFA, which cannot be recognized by any deterministic variant of the same type.}, language = {en} } @article{BordihnHolzer2021, author = {Bordihn, Henning and Holzer, Markus}, title = {On the number of active states in finite automata}, series = {Acta informatica}, volume = {58}, journal = {Acta informatica}, number = {4}, publisher = {Springer}, address = {Berlin ; Heidelberg [u.a.]}, issn = {0001-5903}, doi = {10.1007/s00236-021-00397-8}, pages = {301 -- 318}, year = {2021}, abstract = {We introduce a new measure of descriptional complexity on finite automata, called the number of active states. Roughly speaking, the number of active states of an automaton A on input w counts the number of different states visited during the most economic computation of the automaton A for the word w. This concept generalizes to finite automata and regular languages in a straightforward way. We show that the number of active states of both finite automata and regular languages is computable, even with respect to nondeterministic finite automata. We further compare the number of active states to related measures for regular languages. In particular, we show incomparability to the radius of regular languages and that the difference between the number of active states and the total number of states needed in finite automata for a regular language can be of exponential order.}, language = {en} } @phdthesis{Bordihn2011, author = {Bordihn, Henning}, title = {Contributions to the syntactical analysis beyond context-freeness}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-59719}, school = {Universit{\"a}t Potsdam}, year = {2011}, abstract = {Parsability approaches of several grammar formalisms generating also non-context-free languages are explored. Chomsky grammars, Lindenmayer systems, grammars with controlled derivations, and grammar systems are treated. Formal properties of these mechanisms are investigated, when they are used as language acceptors. Furthermore, cooperating distributed grammar systems are restricted so that efficient deterministic parsing without backtracking becomes possible. For this class of grammar systems, the parsing algorithm is presented and the feature of leftmost derivations is investigated in detail.}, language = {en} } @phdthesis{Blum2010, author = {Blum, Niklas}, title = {Formalization of a converged internet and telecommunications service environment}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-51146}, school = {Universit{\"a}t Potsdam}, year = {2010}, abstract = {The programmable network envisioned in the 1990s within standardization and research for the Intelligent Network is currently coming into reality using IPbased Next Generation Networks (NGN) and applying Service-Oriented Architecture (SOA) principles for service creation, execution, and hosting. SOA is the foundation for both next-generation telecommunications and middleware architectures, which are rapidly converging on top of commodity transport services. Services such as triple/quadruple play, multimedia messaging, and presence are enabled by the emerging service-oriented IPMultimedia Subsystem (IMS), and allow telecommunications service providers to maintain, if not improve, their position in the marketplace. SOA becomes the de facto standard in next-generation middleware systems as the system model of choice to interconnect service consumers and providers within and between enterprises. We leverage previous research activities in overlay networking technologies along with recent advances in network abstraction, service exposure, and service creation to develop a paradigm for a service environment providing converged Internet and Telecommunications services that we call Service Broker. Such a Service Broker provides mechanisms to combine and mediate between different service paradigms from the two domains Internet/WWW and telecommunications. Furthermore, it enables the composition of services across these domains and is capable of defining and applying temporal constraints during creation and execution time. By adding network-awareness into the service fabric, such a Service Broker may also act as a next generation network-to-service element allowing the composition of crossdomain and cross-layer network and service resources. The contribution of this research is threefold: first, we analyze and classify principles and technologies from Information Technologies (IT) and telecommunications to identify and discuss issues allowing cross-domain composition in a converging service layer. Second, we discuss service composition methods allowing the creation of converged services on an abstract level; in particular, we present a formalized method for model-checking of such compositions. Finally, we propose a Service Broker architecture converging Internet and Telecom services. This environment enables cross-domain feature interaction in services through formalized obligation policies acting as constraints during service discovery, creation, and execution time.}, language = {en} } @article{Blaese2014, author = {Blaese, Leif}, title = {Data mining for unidentified protein squences}, series = {Process design for natural scientists: an agile model-driven approach}, journal = {Process design for natural scientists: an agile model-driven approach}, number = {500}, publisher = {Springer}, address = {Berlin}, isbn = {978-3-662-45005-5}, issn = {1865-0929}, pages = {73 -- 87}, year = {2014}, abstract = {Through the use of next generation sequencing (NGS) technology, a lot of newly sequenced organisms are now available. Annotating those genes is one of the most challenging tasks in sequence biology. Here, we present an automated workflow to find homologue proteins, annotate sequences according to function and create a three-dimensional model.}, language = {en} } @phdthesis{Bickel2008, author = {Bickel, Steffen}, title = {Learning under differing training and test distributions}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-33331}, school = {Universit{\"a}t Potsdam}, year = {2008}, abstract = {One of the main problems in machine learning is to train a predictive model from training data and to make predictions on test data. Most predictive models are constructed under the assumption that the training data is governed by the exact same distribution which the model will later be exposed to. In practice, control over the data collection process is often imperfect. A typical scenario is when labels are collected by questionnaires and one does not have access to the test population. For example, parts of the test population are underrepresented in the survey, out of reach, or do not return the questionnaire. In many applications training data from the test distribution are scarce because they are difficult to obtain or very expensive. Data from auxiliary sources drawn from similar distributions are often cheaply available. This thesis centers around learning under differing training and test distributions and covers several problem settings with different assumptions on the relationship between training and test distributions-including multi-task learning and learning under covariate shift and sample selection bias. Several new models are derived that directly characterize the divergence between training and test distributions, without the intermediate step of estimating training and test distributions separately. The integral part of these models are rescaling weights that match the rescaled or resampled training distribution to the test distribution. Integrated models are studied where only one optimization problem needs to be solved for learning under differing distributions. With a two-step approximation to the integrated models almost any supervised learning algorithm can be adopted to biased training data. In case studies on spam filtering, HIV therapy screening, targeted advertising, and other applications the performance of the new models is compared to state-of-the-art reference methods.}, language = {en} } @phdthesis{Awad2010, author = {Awad, Ahmed Mahmoud Hany Aly}, title = {A compliance management framework for business process models}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-49222}, school = {Universit{\"a}t Potsdam}, year = {2010}, abstract = {Companies develop process models to explicitly describe their business operations. In the same time, business operations, business processes, must adhere to various types of compliance requirements. Regulations, e.g., Sarbanes Oxley Act of 2002, internal policies, best practices are just a few sources of compliance requirements. In some cases, non-adherence to compliance requirements makes the organization subject to legal punishment. In other cases, non-adherence to compliance leads to loss of competitive advantage and thus loss of market share. Unlike the classical domain-independent behavioral correctness of business processes, compliance requirements are domain-specific. Moreover, compliance requirements change over time. New requirements might appear due to change in laws and adoption of new policies. Compliance requirements are offered or enforced by different entities that have different objectives behind these requirements. Finally, compliance requirements might affect different aspects of business processes, e.g., control flow and data flow. As a result, it is infeasible to hard-code compliance checks in tools. Rather, a repeatable process of modeling compliance rules and checking them against business processes automatically is needed. This thesis provides a formal approach to support process design-time compliance checking. Using visual patterns, it is possible to model compliance requirements concerning control flow, data flow and conditional flow rules. Each pattern is mapped into a temporal logic formula. The thesis addresses the problem of consistency checking among various compliance requirements, as they might stem from divergent sources. Also, the thesis contributes to automatically check compliance requirements against process models using model checking. We show that extra domain knowledge, other than expressed in compliance rules, is needed to reach correct decisions. In case of violations, we are able to provide a useful feedback to the user. The feedback is in the form of parts of the process model whose execution causes the violation. In some cases, our approach is capable of providing automated remedy of the violation.}, language = {en} }