Dokument-ID Dokumenttyp Verfasser/Autoren Herausgeber Haupttitel Abstract Auflage Verlagsort Verlag Erscheinungsjahr Seitenzahl Schriftenreihe Titel Schriftenreihe Bandzahl ISBN Quelle der Hochschulschrift Konferenzname Quelle:Titel Quelle:Jahrgang Quelle:Heftnummer Quelle:Erste Seite Quelle:Letzte Seite URN DOI Abteilungen
OPUS4-1428 Wissenschaftlicher Artikel Arnold, Holger A linearized DPLL calculus with learning This paper describes the proof calculus LD for clausal propositional logic, which is a linearized form of the well-known DPLL calculus extended by clause learning. It is motivated by the demand to model how current SAT solvers built on clause learning are working, while abstracting from decision heuristics and implementation details. The calculus is proved sound and terminating. Further, it is shown that both the original DPLL calculus and the conflict-directed backtracking calculus with clause learning, as it is implemented in many current SAT solvers, are complete and proof-confluent instances of the LD calculus. 2007 urn:nbn:de:kobv:517-opus-15421 Institut für Informatik und Computational Science
OPUS4-11668 Wissenschaftlicher Artikel Gressmann, Jean; Janhunen, Tomi; Mercer, Robert E.; Schaub, Torsten; Thiele, Sven; Tichy, Richard On probing and multi-threading in platypus 2006 Institut für Informatik und Computational Science
OPUS4-11640 Wissenschaftlicher Artikel Grell, Susanne; Schaub, Torsten; Selbig, Joachim Modelling biological networks by action languages via set programming 2006 10.1007/11799573 Institut für Informatik und Computational Science
OPUS4-11605 Wissenschaftlicher Artikel Delgrande, James Patrick; Schaub, Torsten; Tompits, Hans A Preference-Based Framework for Updating logic Programs : preliminary reports 2006 Institut für Informatik und Computational Science
OPUS4-11925 Wissenschaftlicher Artikel Anger, Christian; Gebser, Martin; Schaub, Torsten Approaching the core of unfounded sets 2006 Institut für Informatik und Computational Science
OPUS4-11957 Wissenschaftlicher Artikel Shenoy, Pradeep; Krauledat, Matthias; Blankertz, Benjamin; Rao, Rajesh P. N.; Müller, Klaus-Robert Towards adaptive classification for BCI Non-stationarities are ubiquitous in EEG signals. They are especially apparent in the use of EEG-based brain- computer interfaces (BCIs): (a) in the differences between the initial calibration measurement and the online operation of a BCI, or (b) caused by changes in the subject's brain processes during an experiment (e.g. due to fatigue, change of task involvement, etc). In this paper, we quantify for the first time such systematic evidence of statistical differences in data recorded during offline and online sessions. Furthermore, we propose novel techniques of investigating and visualizing data distributions, which are particularly useful for the analysis of (non-) stationarities. Our study shows that the brain signals used for control can change substantially from the offline calibration sessions to online control, and also within a single session. In addition to this general characterization of the signals, we propose several adaptive classification schemes and study their performance on data recorded during online experiments. An encouraging result of our study is that surprisingly simple adaptive methods in combination with an offline feature selection scheme can significantly increase BCI performance 2006 10.1088/1741-2560/3/1/R02 Institut für Informatik und Computational Science
OPUS4-12100 Wissenschaftlicher Artikel Lemm, Steven; Curio, Gabriel; Hlushchuk, Yevhen; Müller, Klaus-Robert Enhancing the signal-to-noise ratio of ICA-based extracted ERPs When decomposing single trial electroencephalography it is a challenge to incorporate prior physiological knowledge. Here, we develop a method that uses prior information about the phase-locking property of event-related potentials in a regularization framework to bias a blind source separation algorithm toward an improved separation of single-trial phase-locked responses in terms of an increased signal-to-noise ratio. In particular, we suggest a transformation of the data, using weighted average of the single trial and trial-averaged response, that redirects the focus of source separation methods onto the subspace of event-related potentials. The practical benefit with respect to an improved separation of such components from ongoing background activity and extraneous noise is first illustrated on artificial data and finally verified in a real-world application of extracting single-trial somatosensory evoked potentials from multichannel EEG-recordings 2006 10.1109/Tbme.2006.870258 Institut für Informatik und Computational Science
OPUS4-12047 Wissenschaftlicher Artikel Bobda, Christophe Special issue on ReCoSoC 2007 : editorial 2009 10.1016/j.micpro.2009.01.001 Institut für Informatik und Computational Science
OPUS4-12051 Wissenschaftlicher Artikel Blankertz, Benjamin; Dornhege, Guido; Krauledat, Matthias; Müller, Klaus-Robert; Kunzmann, Volker; Losch, Florian; Curio, Gabriel The Berlin brain-computer interface : EEG-based communication without subject training The Berlin Brain-Computer Interface (BBCI) project develops a noninvasive BCI system whose key features are 1) the use of well-established motor competences as control paradigms, 2) high-dimensional features from 128-channel electroencephalogram (EEG), and 3) advanced machine learning techniques. As reported earlier, our experiments demonstrate that very high information transfer rates can be achieved using the readiness potential (RP) when predicting the laterality of upcoming left-versus right-hand movements in healthy subjects. A more recent study showed that the RP similarily accompanies phantom movements in arm amputees, but the signal strength decreases with longer loss of the limb. In a complementary approach, oscillatory features are used to discriminate imagined movements (left hand versus right hand versus foot). In a recent feedback study with six healthy subjects with no or very little experience with BCI control, three subjects achieved an information transfer rate above 35 bits per minute (bpm), and further two subjects above 24 and 15 bpm, while one subject could not achieve any BCI control. These results are encouraging for an EEG-based BCI system in untrained subjects that is independent of peripheral nervous system activity and does not rely on evoked potentials even when compared to results with very well-trained subjects operating other BCI systems 2006 10.1109/Tnsre.2006.875557 Institut für Informatik und Computational Science
OPUS4-12174 Wissenschaftlicher Artikel Cordes, Frank; Kaiser, Rolf; Selbig, Joachim Bioinformatics approach to predicting HIV drug resistance The emergence of drug resistance remains one of the most challenging issues in the treatment of HIV-1 infection. The extreme replication dynamics of HIV facilitates its escape from the selective pressure exerted by the human immune system and by the applied combination drug therapy. This article reviews computational methods whose combined use can support the design of optimal antiretroviral therapies based on viral genotypic and phenotypic data. Genotypic assays are based on the analysis of mutations associated with reduced drug susceptibility, but are difficult to interpret due to the numerous mutations and mutational patterns that confer drug resistance. Phenotypic resistance or susceptibility can be experimentally evaluated by measuring the inhibition of the viral replication in cell culture assays. However, this procedure is expensive and time consuming 2006 10.1586/14737159.6.2.207 Institut für Informatik und Computational Science
OPUS4-12217 Wissenschaftlicher Artikel Konczak, Kathrin Weak order equivalence for Logic Programs with Prefernces 2006 Institut für Informatik und Computational Science
OPUS4-12224 Wissenschaftlicher Artikel Gerbser, Martin; Schaub, Torsten Tableau calculi for answer set programming 2006 10.1007/11799573 Institut für Informatik und Computational Science
OPUS4-12204 Wissenschaftlicher Artikel Konczak, Kathrin Voting Theory in Answer Set Programming 2006 Institut für Informatik und Computational Science
OPUS4-12186 Wissenschaftlicher Artikel Gressmann, Jean; Janhunen, Tomi; Mercer, Robert E.; Schaub, Torsten; Thiele, Sven; Tichy, Richard On probing and multi-threading in platypus 2006 Institut für Informatik und Computational Science
OPUS4-12210 Wissenschaftlicher Artikel Anger, Christian; Gebser, Martin; Janhunen, Tomi; Schaub, Torsten What's a head without a body? 2006 Institut für Informatik und Computational Science
OPUS4-12211 Wissenschaftlicher Artikel Gerbser, Martin; Lee, Joohyung; Lierler, Yuliya Elementary sets for logic programs 2006 978-1-57735-281-5 Institut für Informatik und Computational Science
OPUS4-12212 Wissenschaftlicher Artikel Gerbser, Martin; Schaub, Torsten Characterizing (ASP) inferences by unit propagation 2006 Institut für Informatik und Computational Science
OPUS4-12246 Wissenschaftlicher Artikel Meinel, Christoph; Klotz, Volker The first 10 years of the ECCC digital library 2006 10.1145/1107458.1107484 Institut für Informatik und Computational Science
OPUS4-12294 Wissenschaftlicher Artikel Laub, Julian; Roth, Volker; Buhmann, Joachim; Müller, Klaus-Robert On the information and representation of non-Euclidean pairwise data Two common data representations are mostly used in intelligent data analysis, namely the vectorial and the pairwise representation. Pairwise data which satisfy the restrictive conditions of Euclidean spaces can be faithfully translated into a Euclidean vectorial representation by embedding. Non-metric pairwise data with violations of symmetry, reflexivity or triangle inequality pose a substantial conceptual problem for pattern recognition since the amount of predictive structural information beyond what can be measured by embeddings is unclear. We show by systematic modeling of non-Euclidean pairwise data that there exists metric violations which can carry valuable problem specific information. Furthermore, Euclidean and non-metric data can be unified on the level of structural information contained in the data. Stable component analysis selects linear subspaces which are particularly insensitive to data fluctuations. Experimental results from different domains support our pattern recognition strategy. 2006 10.1016/j.patcog.2006.04.016 Institut für Informatik und Computational Science
OPUS4-12242 Wissenschaftlicher Artikel Rozinat, A; Van der Aalst, Wil M. P. Conformance testing: Measuring the fit and appropriateness of event logs and process models Most information systems log events (e.g., transaction logs, audit traits) to audit and monitor the processes they support. At the same time, many of these processes have been explicitly modeled. For example, SAP R/3 logs events in transaction logs and there are EPCs (Event-driven Process Chains) describing the so-called reference models. These reference models describe how the system should be used. The coexistence of event logs and process models raises an interesting question: "Does the event log conform to the process model and vice versa?". This paper demonstrates that there is not a simple answer to this question. To tackle the problem, we distinguish two dimensions of conformance: fitness (the event log may be the result of the process modeled) and appropriateness (the model is a likely candidate from a structural and behavioral point of view). Different metrics have been defined and a Conformance Checker has been implemented within the ProM Framework 2006 Institut für Informatik und Computational Science
OPUS4-12263 Wissenschaftlicher Artikel Willig, Andreas; Mitschke, Robert Results of bit error measurements with sensor nodes and casuistic consequences for design of energy-efficient error control schemes For the proper design of energy-efficient error control schemes some insight into channel error patterns is needed. This paper presents bit error and packet loss measurements taken with sensor nodes running the popular RFM 2006 978-3-540-32158-3 Institut für Informatik und Computational Science
OPUS4-12328 Wissenschaftlicher Artikel Delgrande, James Patrick; Liu, Daphne H.; Schaub, Torsten; Thiele, Sven COBA 2.0 : a consistency-based belief change system 2006 Institut für Informatik und Computational Science
OPUS4-12329 Wissenschaftlicher Artikel Delgrande, James Patrick; Schaub, Torsten; Tompits, Hans An Extended Query language for action languages (and its application to aggregates and preferences) 2006 Institut für Informatik und Computational Science
OPUS4-12330 Wissenschaftlicher Artikel Mileo, Alessandra; Schaub, Torsten Extending ordered disjunctions for policy enforcement : preliminary report 2006 Institut für Informatik und Computational Science
OPUS4-12379 Wissenschaftlicher Artikel Luckow, André; Schnor, Bettina Migol : a Fault Tolerant Service Framework for Grid Computing : Evolution to WSRF (2006) 2006 Institut für Informatik und Computational Science
OPUS4-12381 Wissenschaftlicher Artikel Hallama, Nicole; Luckow, André; Schnor, Bettina Grid Security for Fault Tolerant Grid Applications 2006 978-1-880843-60-4 Institut für Informatik und Computational Science
OPUS4-12322 Wissenschaftlicher Artikel Meinel, Christoph; Wang, Long Building content clusters based on modelling page pairs We give a new view on building content clusters from page pair models. We measure the heuristic importance within every two pages by computing the distance of their accessed positions in usage sessions. We also compare our page pair models with the classical pair models used in information theories and natural language processing, and give different evaluation methods to build the reasonable content communities. And we finally interpret the advantages and disadvantages of our models from detailed experiment results 2006 10.1007/11610113_85 Institut für Informatik und Computational Science
OPUS4-12324 Wissenschaftlicher Artikel Kawanabe, Motoaki; Blanchard, Gilles; Sugiyama, Masashi; Spokoiny, Vladimir G.; Müller, Klaus-Robert A novel dimension reduction procedure for searching non-Gaussian subspaces In this article, we consider high-dimensional data which contains a low-dimensional non-Gaussian structure contaminated with Gaussian noise and propose a new linear method to identify the non-Gaussian subspace. Our method NGCA (Non-Gaussian Component Analysis) is based on a very general semi-parametric framework and has a theoretical guarantee that the estimation error of finding the non-Gaussian components tends to zero at a parametric rate. NGCA can be used not only as preprocessing for ICA, but also for extracting and visualizing more general structures like clusters. A numerical study demonstrates the usefulness of our method 2006 10.1007/11679363_19 Institut für Informatik und Computational Science
OPUS4-12373 Wissenschaftlicher Artikel Pernici, Barbara; Weske, Mathias Business process management 2006 Institut für Informatik und Computational Science
OPUS4-12362 Wissenschaftlicher Artikel Friedrich, Sven; Krahmer, Sebastian; Schneidenbach, Lars; Schnor, Bettina Loaded: Server Load Balancing for IPv6 With the next generation Internet protocol IPv6 at the horizon, it is time to think about how applications can migrate to IPv6. Web traffic is currently one of the most important applications in the Internet. The increasing popularity of dynamically generated content on the World Wide Web, has created the need for fast web servers. Server clustering together with server load balancing has emerged as a promising technique to build scalable web servers. The paper gives a short overview over the new features of IPv6 and different server load balancing technologies. Further, we present and evaluate Loaded, an user-space server load balancer for IPv4 and IPv6 based on Linux. 2006 0-7695-2622-5 Institut für Informatik und Computational Science
OPUS4-12420 Wissenschaftlicher Artikel Delgrande, James Patrick; Schaub, Torsten; Tompits, Hans A preference-based framework for updating logic programs 2007 978-3-540- 72199-4 Institut für Informatik und Computational Science
OPUS4-12464 Wissenschaftlicher Artikel Mileo, Alessandra; Schaub, Torsten Qualitative constraint enforcement in advanced policy specification 2007 Institut für Informatik und Computational Science
OPUS4-12466 Wissenschaftlicher Artikel Delgrande, James Patrick; Lang, Jérôme; Schaub, Torsten Belief change based on global minimisation 2007 Institut für Informatik und Computational Science
OPUS4-12482 Wissenschaftlicher Artikel Gebser, Martin; Schaub, Torsten; Thiele, Sven GrinGo : a new grounder for answer set programming 2007 978-3-540- 72199-4 Institut für Informatik und Computational Science
OPUS4-12501 Wissenschaftlicher Artikel Konczak, Kathrin; Linke, Thomas; Schaub, Torsten Graphs and colorings for answer set programming We investigate the usage of rule dependency graphs and their colorings for characterizing and computing answer sets of logic programs. This approach provides us with insights into the interplay between rules when inducing answer sets. We start with different characterizations of answer sets in terms of totally colored dependency graphs that differ ill graph-theoretical aspects. We then develop a series of operational characterizations of answer sets in terms of operators on partial colorings. In analogy to the notion of a derivation in proof theory, our operational characterizations are expressed as (non-deterministically formed) sequences of colorings, turning an uncolored graph into a totally colored one. In this way, we obtain an operational framework in which different combinations of operators result in different formal properties. Among others, we identify the basic strategy employed by the noMoRe system and justify its algorithmic approach. Furthermore, we distinguish operations corresponding to Fitting's operator as well as to well-founded semantics 2006 10.1017/S1471068405002528 Institut für Informatik und Computational Science
OPUS4-12688 Wissenschaftlicher Artikel Schneidenbach, Lars; Schnor, Bettina Migration of MPI Applications to IPv6 Networks 2005 0-88986-468-3 Institut für Informatik und Computational Science
OPUS4-12845 Wissenschaftlicher Artikel Anger, Christian; Gebser, Martin; Linke, Thomas; Neumann, Andre; Schaub, Torsten The nomore++ approach to answer set solving 2005 Institut für Informatik und Computational Science
OPUS4-12877 Wissenschaftlicher Artikel Häger, Sebastian; Schubert, Wolfgang Assoziationen in Softwarearchitekturen Potsdam Univ. 2005 33 S. Preprint / Universität Potsdam, Institut für Informatik 2005, 2 Institut für Informatik und Computational Science
OPUS4-12904 Wissenschaftlicher Artikel Camales, Renaud Explicit formulation of the solution of Hamada-Leray-Wagschal's theorem In this paper, an explicit formula of the solution of Hainada-Leray-Wagschal's theorem is given. For this, only structure's theorem of finite dimensional determination's function and linear algebra technics developped in [1] are used 2005 Institut für Informatik und Computational Science
OPUS4-13157 Wissenschaftlicher Artikel Konczak, Kathrin; Vogel, Ralf Abduction and Preferences in Linguistics 2005 Institut für Informatik und Computational Science
OPUS4-13270 Wissenschaftlicher Artikel Konczak, Kathrin; Lang, Jerome Voting procedures with incomplete preferences 2005 Institut für Informatik und Computational Science
OPUS4-13271 Wissenschaftlicher Artikel Konczak, Kathrin; Vogel, Ralf Abduction and preferences in linguistics : Extended abstract 2005 Institut für Informatik und Computational Science
OPUS4-13272 Wissenschaftlicher Artikel Gressmann, Jean; Janhunen, Tomi; Mercer, Robert E.; Schaub, Torsten; Thiele, Sven; Tichy, Richard Platypus : a platform for distributed answer set solving 2005 Institut für Informatik und Computational Science
OPUS4-13273 Wissenschaftlicher Artikel Anger, Christian; Gebser, Martin; Linke, Thomas; Neumann, Andre; Schaub, Torsten The nomore++ approach to answer set solving 2005 Institut für Informatik und Computational Science
OPUS4-13274 Wissenschaftlicher Artikel Grell, Susanne; Konczak, Kathrin; Schaub, Torsten nomore) : a system for computing preferred Answer Sets 2005 Institut für Informatik und Computational Science
OPUS4-13275 Wissenschaftlicher Artikel Faber, Wolfgang; Konczak, Kathrin Strong Equivalence for Logic Programs with Preferences 2005 Institut für Informatik und Computational Science
OPUS4-13276 Wissenschaftlicher Artikel Anger, Christian; Konczak, Kathrin; Linke, Thomas; Schaub, Torsten A Glimpse of Answer Set Programming 2005 Institut für Informatik und Computational Science
OPUS4-13407 Wissenschaftlicher Artikel Goessel, Michael; Morozov, A. V.; Sapozhnikov, V. V.; Sapozhaikov, Vl. V. Checking combinational circuits by the method of logic complement Design of fully self-testing combinational circuits was considered. A theorem defining the conditions for guaranteed logic complement-based design of fully self-testing circuit was proved. Examples were presented 2005 Institut für Informatik und Computational Science
OPUS4-13481 Wissenschaftlicher Artikel Scheffler, Thomas; Schnor, Bettina Privacy Requirements for Embedded Sensor Devices This paper analyses data privacy issues as they arise from different deployment scenarios for networks that use embedded sensor devices. Maintaining data privacy in pervasive environments requires the management and implementation of privacy protection measures close to the data source. We propose a set of atomic privacy parameters that is generic enough to form specific privacy classes and might be applied directly at the embedded sensor device. 2005 978-3-800729-09-8 Institut für Informatik und Computational Science
OPUS4-13544 Wissenschaftlicher Artikel Calude, C. S.; Jurgensen, Helmut Is complexity a source of incompleteness? In this paper we prove Chaitin's "heuristic principle," the theorems of a finitely-specified theory cannot be significantly more complex than the theory itself, for an appropriate measure of complexity. We show that the measure is invariant under the change of the Godel numbering. For this measure, the theorems of a finitely-specified, sound, consistent theory strong enough to formalize arithmetic which is arithmetically sound (like Zermelo-Fraenkel set theory with choice or Peano Arithmetic) have bounded complexity, hence every sentence of the theory which is significantly more complex than the theory is unprovable. Previous results showing that incompleteness is not accidental, but ubiquitous are here reinforced in probabilistic terms: the probability that a true sentence of length n is provable in the theory tends to zero when n tends to infinity, while the probability that a sentence of length n is true is strictly positive. (c) 2004 Elsevier Inc. All rights reserved 2005 Institut für Informatik und Computational Science
OPUS4-13558 Wissenschaftlicher Artikel Delgrande, James Patrick; Schaub, Torsten Expressing default logic variants in default logic Reiter's default logic is one of the best known and most studied of the approaches to nonmonotonic reasoning. Several variants of default logic have subsequently been proposed to give systems with properties differing from the original. In this paper, we examine the relationship between default logic and its major variants. We accomplish this by translating a default theory under a variant interpretation into a second default theory, under the original Reiter semantics, wherein the variant interpretation is respected. That is, in each case we show that, given an extension of a translated theory, one may extract an extension of the original variant default logic theory. We show how constrained, rational, justified, and cumulative default logic can be expressed in Reiter's default logic. As well, we show how Reiter's default logic can be expressed in rational default logic. From this, we suggest that any such variant can be similarly treated. Consequently, we provide a unification of default logics, showing how the original formulation of default logic may express its variants. Moreover, the translations clearly express the relationships between alternative approaches to default logic. The translations themselves are shown to generally have good properties. Thus, in at least a theoretical sense, we show that these variants are in a sense superfluous, in that for any of these variants of default logic, we can exactly mimic the behaviour of a variant in standard default logic. As well, the translations lend insight into means of classifying the expressive power of default logic variants; specifically we suggest that the property of semi-monotonicity represents a division with respect to expressibility, whereas regularity and cumulativity do not 2005 Institut für Informatik und Computational Science
OPUS4-13567 Wissenschaftlicher Artikel Döllner, Jürgen Geospatial digital rights management in geovisualization Geovisualization offers powerful tools, techniques, and strategies to present, explore, analyze, and manage geoinformation. Interactive geovirtual environments such as virtual 3D maps or virtual 3D city models, however, raise the question how to control geodata usage and distribution. We present a concept for embedding digital rights in geovisualizations. It is based on geo-documents, an object-oriented scheme to specify a wide range of geo visualizations. Geo-documents are assembled by building blocks categorized into presentation, structure, interaction, animation, and Digital Rights Management (DRM) classes. DRM objects allow for defining permissions and constraints for all objects contained in geo-documents. In this way, authors of geo visualizations can control how their geo-documents are used, personalized, and redistributed by users. The strengths of the presented concept include the ability to integrate heterogeneous 2D and 3D geodata within a compact design scheme and the ability to cope with privacy, security, and copyright issues. Embedded digital rights in geovisualizations can be applied to improve the usability of geodata user interfaces, to implement publisher-subscriber communication systems for geodata, and to establish business models for geodata trading systems 2005 Institut für Informatik und Computational Science
OPUS4-13530 Wissenschaftlicher Artikel Bruggemeier, M.; Dovifat, A.; Kubisch, D. Micropolitical innovation arenas as a tool for analyzing innovation processes in the context of electronic government E-Government requires technical and organizational innovation. Research has already shown that the respective innovation process is complex and contingent upon specific organizational structures. Managing such innovation processes successfully is difficult. Drawing on assumptions of micropolitical behavior, a framework of innovation arenas is proposed. It supports the analysis of ongoing E-Government projects as well as the ex post investigation of successful or failed projects. Testing this framework in case studies already demonstrates its usefulness for individual actors making strategic choices about change management. Furthermore, the results indicate that many commonly held assumptions about successful change management have to be reconsidered 2005 Institut für Informatik und Computational Science
OPUS4-13533 Wissenschaftlicher Artikel Brzozowski, J. A.; Jürgensen, Helmut Representation of semiautomata by canonical words and equivalences We study a novel representation of semiautomata, which is motivated by the method of trace-assertion specifications of software modules. Each state of the semiautomaton is represented by an arbitrary word leading to that state, the canonical word. The transitions of the semiautomaton give rise to a right congruence, the state-equivalence, on the set of input words of the semiautomaton: two words are state-equivalent if and only if they lead to the same state. We present a simple algorithm for finding a set of generators for state-equivalence. Directly from this set of generators, we construct a confluent prefix-rewriting system which permits us to transform any word to its canonical representative. In general, the rewriting system may allow infinite derivations. To address this issue, we impose the condition of prefix-continuity on the set of canonical words. A set is prefix-continuous if, whenever a word w and a prefix u of w axe in the set, then all the prefixes of w longer than u are also in the set. Prefix-continuous sets include prefix-free and prefix-closed sets as special cases. We prove that the rewriting system is Noetherian if and only if the set of canonical words is prefix-continuous. Furthermore, if the set of canonical words is prefix- continuous, then the set of rewriting rules is irredundant. We show that each prefix-continuous canonical set corresponds to a spanning forest of the semiautomaton 2005 Institut für Informatik und Computational Science
OPUS4-13511 Wissenschaftlicher Artikel Bordihn, Henning On the number of components in cooperating distributed grammar systems It is proved that the number of components in context-free cooperating distributed (CD) grammar systems can be reduced to 3 when they are working in the so-called sf-mode of derivation, which is the cooperation protocol which has been considered first for CD grammar systems. In this derivation mode, a component continues the derivation until and unless there is a nonterminal in the sentential form which cannot be rewritten according to that component. Moreover, it is shown that CD grammar systems in sf-mode with only one component can generate only the context-free languages but they can generate non-context-free languages if two components are used. The sf-mode of derivation is compared with other well-known cooperation protocols with respect to the hierarchies induced by the number of components. (C) 2004 Elsevier B.V. All rights reserved 2005 Institut für Informatik und Computational Science
OPUS4-13512 Wissenschaftlicher Artikel Bordihn, Henning; Holzer, Markus; Kutrib, Martin Unsolvability levels of operation problems for subclasses of context-free languages We investigate the operation problem for linear and deterministic context-free languages: Fix an operation on formal languages. Given linear (deterministic, respectively) context-free languages, is the application of this operation to the given languages still a linear (deterministic, respectively) context-free language? Besides the classical operations, for which the linear and deterministic context-free languages are not closed, we also consider the recently introduced root and power operation. We show non-semidecidability, to be more precise, we show completeness for the second level of the arithmetic hierarchy for all of the aforementioned operations, except for the power operation, if the underlying alphabet contains at least two letters. The result for the power opera, tion solves an open problem stated in Theoret. Comput. Sci. 314 (2004) 445-449 2005 Institut für Informatik und Computational Science
OPUS4-13495 Wissenschaftlicher Artikel Beerenwinkel, Niko; Sing, Tobias; Lengauer, Thomas; Rahnenfuhrer, Joerg; Roomp, Kirsten; Savenkov, Igor; Fischer, Roman; Hoffmann, Daniel; Selbig, Joachim; Korn, Klaus; Walter, Hauke; Berg, Thomas; Braun, Patrick; Faetkenheuer, Gerd; Oette, Mark; Rockstroh, Juergen; Kupfer, Bernd; Kaiser, Rolf; Daeumer, Martin Computational methods for the design of effective therapies against drug resistant HIV strains The development of drug resistance is a major obstacle to successful treatment of HIV infection. The extraordinary replication dynamics of HIV facilitates its escape from selective pressure exerted by the human immune system and by combination drug therapy. We have developed several computational methods whose combined use can support the design of optimal antiretroviral therapies based on viral genomic data 2005 Institut für Informatik und Computational Science
OPUS4-13620 Wissenschaftlicher Artikel Gebser, Martin; Liu, Lengning; Namasivayam, Gayathri; Neumann, André; Schaub, Torsten; Truszczynski, Miroslaw The first answer set programming system competition 2007 978-3-540- 72199-4 Institut für Informatik und Computational Science
OPUS4-13750 Wissenschaftlicher Artikel Lemm, Steven; Blankertz, Benjamin; Curio, Gabriel; Müller, Klaus-Robert Spatio-spectral filters for improving the classification of single trial EEG Data recorded in electroencephalogram (EEG)-based brain-computer interface experiments is generally very noisy, non-stationary, and contaminated with artifacts that can deteriorate discrimination/classification methods. In this paper, we extend the common spatial pattern (CSP) algorithm with the aim to alleviate these adverse effects. In particular, we suggest an extension of CSP to the state space, which utilizes the method of time delay embedding. As we will show, this allows for individually tuned frequency filters at each electrode position and, thus, yields an improved and more robust machine learning procedure. The advantages of the proposed method over the original CSP method are verified in terms of an improved information transfer rate (bits per trial) on a set of EEG-recordings from experiments of imagined limb movements 2005 Institut für Informatik und Computational Science
OPUS4-35178 Wissenschaftlicher Artikel Kiertscher, Simon; Zinke, Jörg; Schnor, Bettina CHERUB power consumption aware cluster resource management This paper presents an evaluation of ACPI energy saving modes, and deduces the design and implementation of an energy saving daemon for clusters called cherub. The design of the cherub daemon is modular and extensible. Since the only requirement is a central approach for resource management, cherub is suited for Server Load Balancing (SLB) clusters managed by dispatchers like Linux Virtual Server (LVS), as well as for High Performance Computing (HPC) clusters. Our experimental results show that cherub's scheduling algorithm works well, i.e. it will save energy, if possible, and avoids state-flapping. New York Springer 2013 9 Cluster computing : the journal of networks, software tools and applications 16 1 55 63 10.1007/s10586-011-0176-5 Institut für Informatik und Computational Science
OPUS4-35220 Wissenschaftlicher Artikel Steinert, Bastian; Cassou, Damien; Hirschfeld, Robert CoExist overcoming aversion to change preserving immediate access to source code and run-time information of previous development states Programmers make many changes to the program to eventually find a good solution for a given task. In this course of change, every intermediate development state can of value, when, for example, a promising ideas suddenly turn out inappropriate or the interplay of objects turns out more complex than initially expected before making changes. Programmers would benefit from tool support that provides immediate access to source code and run-time of previous development states of interest. We present IDE extensions, implemented for Squeak/Smalltalk, to preserve, retrieve, and work with this information. With such tool support, programmers can work without worries because they can rely on tools that help them with whatever their explorations will reveal. They no longer have to follow certain best practices only to avoid undesired consequences of changing code. New York Association for Computing Machinery 2013 11 ACM SIGPLAN notices 48 2 107 117 10.1145/2480360.2384591 Institut für Informatik und Computational Science
OPUS4-35754 Wissenschaftlicher Artikel Gebser, Martin; Kaufmann, Benjamin; Schaub, Torsten Conflict-driven answer set solving: From theory to practice We introduce an approach to computing answer sets of logic programs, based on concepts successfully applied in Satisfiability (SAT) checking. The idea is to view inferences in Answer Set Programming (ASP) as unit propagation on nogoods. This provides us with a uniform constraint-based framework capturing diverse inferences encountered in ASP solving. Moreover, our approach allows us to apply advanced solving techniques from the area of SAT. As a result, we present the first full-fledged algorithmic framework for native conflict-driven ASP solving. Our approach is implemented in the ASP solver clasp that has demonstrated its competitiveness and versatility by winning first places at various solver contests. Amsterdam Elsevier 2012 38 Artificial intelligence 187 8 52 89 10.1016/j.artint.2012.04.001 Institut für Informatik und Computational Science
OPUS4-35775 Wissenschaftlicher Artikel Ostrowski, Max; Schaub, Torsten ASP modulo CSP The clingcon system We present the hybrid ASP solver clingcon, combining the simple modeling language and the high performance Boolean solving capacities of Answer Set Programming (ASP) with techniques for using non-Boolean constraints from the area of Constraint Programming (CP). The new clingcon system features an extended syntax supporting global constraints and optimize statements for constraint variables. The major technical innovation improves the interaction between ASP and CP solver through elaborated learning techniques based on irreducible inconsistent sets. A broad empirical evaluation shows that these techniques yield a performance improvement of an order of magnitude. New York Cambridge Univ. Press 2012 19 Theory and practice of logic programming 12 485 503 10.1017/S1471068412000142 Institut für Informatik und Computational Science
OPUS4-35776 Wissenschaftlicher Artikel Gebser, Martin; Kaufmann, Benjamin; Schaub, Torsten Multi-threaded ASP solving with clasp We present the new multi-threaded version of the state-of-the-art answer set solver clasp. We detail its component and communication architecture and illustrate how they support the principal functionalities of clasp. Also, we provide some insights into the data representation used for different constraint types handled by clasp. All this is accompanied by an extensive experimental analysis of the major features related to multi-threading in clasp. New York Cambridge Univ. Press 2012 21 Theory and practice of logic programming 12 8 525 545 10.1017/S1471068412000166 Institut für Informatik und Computational Science
OPUS4-36747 Wissenschaftlicher Artikel Mileo, Alessandra; Schaub, Torsten; Merico, Davide; Bisiani, Roberto Knowledge-based multi-criteria optimization to support indoor positioning Indoor position estimation constitutes a central task in home-based assisted living environments. Such environments often rely on a heterogeneous collection of low-cost sensors whose diversity and lack of precision has to be compensated by advanced techniques for localization and tracking. Although there are well established quantitative methods in robotics and neighboring fields for addressing these problems, they lack advanced knowledge representation and reasoning capacities. Such capabilities are not only useful in dealing with heterogeneous and incomplete information but moreover they allow for a better inclusion of semantic information and more general homecare and patient-related knowledge. We address this problem and investigate how state-of-the-art localization and tracking methods can be combined with Answer Set Programming, as a popular knowledge representation and reasoning formalism. We report upon a case-study and provide a first experimental evaluation of knowledge-based position estimation both in a simulated as well as in a real setting. Dordrecht Springer 2011 26 Annals of mathematics and artificial intelligence 62 3-4 345 370 10.1007/s10472-011-9241-2 Institut für Informatik und Computational Science
OPUS4-36748 Wissenschaftlicher Artikel Polyvyanyy, Artem; Weidlich, Matthias; Weske, Mathias Connectivity of workflow nets the foundations of stepwise verification Behavioral models capture operational principles of real-world or designed systems. Formally, each behavioral model defines the state space of a system, i.e., its states and the principles of state transitions. Such a model is the basis for analysis of the system's properties. In practice, state spaces of systems are immense, which results in huge computational complexity for their analysis. Behavioral models are typically described as executable graphs, whose execution semantics encodes a state space. The structure theory of behavioral models studies the relations between the structure of a model and the properties of its state space. In this article, we use the connectivity property of graphs to achieve an efficient and extensive discovery of the compositional structure of behavioral models; behavioral models get stepwise decomposed into components with clear structural characteristics and inter-component relations. At each decomposition step, the discovered compositional structure of a model is used for reasoning on properties of the whole state space of the system. The approach is exemplified by means of a concrete behavioral model and verification criterion. That is, we analyze workflow nets, a well-established tool for modeling behavior of distributed systems, with respect to the soundness property, a basic correctness property of workflow nets. Stepwise verification allows the detection of violations of the soundness property by inspecting small portions of a model, thereby considerably reducing the amount of work to be done to perform soundness checks. Besides formal results, we also report on findings from applying our approach to an industry model collection. New York Springer 2011 30 Acta informatica 48 4 213 242 10.1007/s00236-011-0137-8 Institut für Informatik und Computational Science
OPUS4-36787 Wissenschaftlicher Artikel Hocher, Berthold; Heiden, S.; von Websky, Karoline; Rahnenführer, Jörg; Kalk, Philipp; Pfab, T. Dual endothelin-converting enzyme/neutral endopeptidase blockade in rats with D-galactosamine-induced liver failure Secondary activation of the endothelin system is thought to be involved in toxic liver injury. This study tested the hypothesis that dual endothelin-converting enzyme / neutral endopeptidase blockade might: be able to attenuate acute toxic liver injury. Male Sprague-Dawley rats were implanted with subcutaneous minipumps to deliver the novel compound SLV338 (10 mg/kg*d) or vehicle. Four days later they received two intraperitoneal injections of D-galactosamine (1.3 g/kg each) or vehicle at an interval of 12 hours. The animals were sacrificed 48 hours after the first injection. Injection of D-galactosamine resulted in very severe liver injury, reflected by strongly elevated plasma liver enzymes, hepatic necrosis and inflammation, and a mortality rate of 42.9 %. SLV338 treatment did not show any significant effect on the extent of acute liver injury as judged from plasma parameters, hepatic histology and mortality. Plasma measurements of SLV338 confirmed adequate drug delivery. Plasma concentrations of big endothelin-1 and endothelin-1 were significantly elevated in animals with liver injury (5-fold and 62-fold, respectively). Plasma endothelin-1 was significantly correlated with several markers of liver injury. SLV338 completely prevented the rise of plasma big endothelin-1 (p<0.05) and markedly attenuated the rise of endothelin-1 (p = 0.055). In conclusion, dual endothelin-converting enzyme / neutral endopeptidase blockade by SLV338 did not significantly attenuate D-galactosamine-induced acute liver injury, although it largely prevented the activation of the endothelin system. An evaluation of SLV338 in a less severe model of liver injury would be of interest, since very severe intoxication might not be relevantly amenable to pharmacological interventions. München Med. Scientific Publ. Holzapfel 2011 5 European journal of medical research : official organ "Deutsche AIDS-Gesellschaft" 16 6 275 279 Institut für Informatik und Computational Science
OPUS4-36760 Wissenschaftlicher Artikel Durzinsky, Markus; Marwan, Wolfgang; Ostrowski, Max; Schaub, Torsten; Wagler, Annegret Automatic network reconstruction using ASP Building biological models by inferring functional dependencies from experimental data is an important issue in Molecular Biology. To relieve the biologist from this traditionally manual process, various approaches have been proposed to increase the degree of automation. However, available approaches often yield a single model only, rely on specific assumptions, and/or use dedicated, heuristic algorithms that are intolerant to changing circumstances or requirements in the view of the rapid progress made in Biotechnology. Our aim is to provide a declarative solution to the problem by appeal to Answer Set Programming (ASP) overcoming these difficulties. We build upon an existing approach to Automatic Network Reconstruction proposed by part of the authors. This approach has firm mathematical foundations and is well suited for ASP due to its combinatorial flavor providing a characterization of all models explaining a set of experiments. The usage of ASP has several benefits over the existing heuristic algorithms. First, it is declarative and thus transparent for biological experts. Second, it is elaboration tolerant and thus allows for an easy exploration and incorporation of biological constraints. Third, it allows for exploring the entire space of possible models. Finally, our approach offers an excellent performance, matching existing, special-purpose systems. New York Cambridge Univ. Press 2011 18 Theory and practice of logic programming 11 749 766 10.1017/S1471068411000287 Institut für Informatik und Computational Science
OPUS4-36761 Wissenschaftlicher Artikel Gebser, Martin; Kaminski, Roland; Schaub, Torsten Complex optimization in answer set programming Preference handling and optimization are indispensable means for addressing nontrivial applications in Answer Set Programming (ASP). However, their implementation becomes difficult whenever they bring about a significant increase in computational complexity. As a consequence, existing ASP systems do not offer complex optimization capacities, supporting, for instance, inclusion-based minimization or Pareto efficiency. Rather, such complex criteria are typically addressed by resorting to dedicated modeling techniques, like saturation. Unlike the ease of common ASP modeling, however, these techniques are rather involved and hardly usable by ASP laymen. We address this problem by developing a general implementation technique by means of meta-prpogramming, thus reusing existing ASP systems to capture various forms of qualitative preferences among answer sets. In this way, complex preferences and optimization capacities become readily available for ASP applications. New York Cambridge Univ. Press 2011 19 Theory and practice of logic programming 11 3 821 839 10.1017/S1471068411000329 Institut für Informatik und Computational Science
OPUS4-37378 Wissenschaftlicher Artikel Baier, Thomas; Mendling, Jan; Weske, Mathias Bridging abstraction layers in process mining While the maturity of process mining algorithms increases and more process mining tools enter the market, process mining projects still face the problem of different levels of abstraction when comparing events with modeled business activities. Current approaches for event log abstraction try to abstract from the events in an automated way that does not capture the required domain knowledge to fit business activities. This can lead to misinterpretation of discovered process models. We developed an approach that aims to abstract an event log to the same abstraction level that is needed by the business. We use domain knowledge extracted from existing process documentation to semi-automatically match events and activities. Our abstraction approach is able to deal with n:m relations between events and activities and also supports concurrency. We evaluated our approach in two case studies with a German IT outsourcing company. (C) 2014 Elsevier Ltd. All rights reserved. Oxford Elsevier 2014 17 Information systems 46 123 139 10.1016/j.is.2014.04.004 Institut für Informatik und Computational Science
OPUS4-34899 Wissenschaftlicher Artikel Sawade, Christoph; Bickel, Steffen; von Oertzen, Timo; Scheffer, Tobias; Landwehr, Niels Active evaluation of ranking functions based on graded relevance Evaluating the quality of ranking functions is a core task in web search and other information retrieval domains. Because query distributions and item relevance change over time, ranking models often cannot be evaluated accurately on held-out training data. Instead, considerable effort is spent on manually labeling the relevance of query results for test queries in order to track ranking performance. We address the problem of estimating ranking performance as accurately as possible on a fixed labeling budget. Estimates are based on a set of most informative test queries selected by an active sampling distribution. Query labeling costs depend on the number of result items as well as item-specific attributes such as document length. We derive cost-optimal sampling distributions for the commonly used performance measures Discounted Cumulative Gain and Expected Reciprocal Rank. Experiments on web search engine data illustrate significant reductions in labeling costs. Dordrecht Springer 2013 24 Machine learning 92 1 41 64 10.1007/s10994-013-5372-5 Institut für Informatik und Computational Science
OPUS4-34920 Wissenschaftlicher Artikel Delikostidis, Ioannis; Engel, Juri; Retsios, Bas; van Elzakker, Corne P. J. M.; Kraak, Menno-Jan; Döllner, Jürgen Increasing the usability of pedestrian navigation interfaces by means of landmark visibility analysis Communicating location-specific information to pedestrians is a challenging task which can be aided by user-friendly digital technologies. In this paper, landmark visibility analysis, as a means for developing more usable pedestrian navigation systems, is discussed. Using an algorithmic framework for image-based 3D analysis, this method integrates a 3D city model with identified landmarks and produces raster visibility layers for each one. This output enables an Android phone prototype application to indicate the visibility of landmarks from the user's actual position. Tested in the field, the method achieves sufficient accuracy for the context of use and improves navigation efficiency and effectiveness. New York Cambridge Univ. Press 2013 15 The journal of navigation 66 4 523 537 10.1017/S0373463313000209 Institut für Informatik und Computational Science
OPUS4-34884 Wissenschaftlicher Artikel Banbara, Mutsunori; Soh, Takehide; Tamura, Naoyuki; Inoue, Katsumi; Schaub, Torsten Answer set programming as a modeling language for course timetabling The course timetabling problem can be generally defined as the task of assigning a number of lectures to a limited set of timeslots and rooms, subject to a given set of hard and soft constraints. The modeling language for course timetabling is required to be expressive enough to specify a wide variety of soft constraints and objective functions. Furthermore, the resulting encoding is required to be extensible for capturing new constraints and for switching them between hard and soft, and to be flexible enough to deal with different formulations. In this paper, we propose to make effective use of ASP as a modeling language for course timetabling. We show that our ASP-based approach can naturally satisfy the above requirements, through an ASP encoding of the curriculum-based course timetabling problem proposed in the third track of the second international timetabling competition (ITC-2007). Our encoding is compact and human-readable, since each constraint is individually expressed by either one or two rules. Each hard constraint is expressed by using integrity constraints and aggregates of ASP. Each soft constraint S is expressed by rules in which the head is the form of penalty (S, V, C), and a violation V and its penalty cost C are detected and calculated respectively in the body. We carried out experiments on four different benchmark sets with five different formulations. We succeeded either in improving the bounds or producing the same bounds for many combinations of problem instances and formulations, compared with the previous best known bounds. New York Cambridge Univ. Press 2013 16 Theory and practice of logic programming 13 2 783 798 10.1017/S1471068413000495 Institut für Informatik und Computational Science
OPUS4-34909 Wissenschaftlicher Artikel Montavon, Gregoire; Braun, Mikio L.; Krüger, Tammo; Müller, Klaus-Robert Analyzing local structure in Kernel-Based learning Piscataway Inst. of Electr. and Electronics Engineers 2013 13 IEEE signal processing magazine 30 4 62 74 10.1109/MSP.2013.2249294 Institut für Informatik und Computational Science
OPUS4-34883 Wissenschaftlicher Artikel Kaminski, Roland; Schaub, Torsten; Siegel, Anne; Videla, Santiago Minimal intervention strategies in logical signaling networks with ASP Proposing relevant perturbations to biological signaling networks is central to many problems in biology and medicine because it allows for enabling or disabling certain biological outcomes. In contrast to quantitative methods that permit fine-grained (kinetic) analysis, qualitative approaches allow for addressing large-scale networks. This is accomplished by more abstract representations such as logical networks. We elaborate upon such a qualitative approach aiming at the computation of minimal interventions in logical signaling networks relying on Kleene's three-valued logic and fixpoint semantics. We address this problem within answer set programming and show that it greatly outperforms previous work using dedicated algorithms. New York Cambridge Univ. Press 2013 16 Theory and practice of logic programming 13 675 690 10.1017/S1471068413000422 Institut für Informatik und Computational Science
OPUS4-35482 Wissenschaftlicher Artikel Fabian, Benjamin; Kunz, Steffen; Konnegen, Marcel; Müller, Sebastian; Günther, Oliver Access control for semantic data federations in industrial product-lifecycle management Information integration across company borders becomes increasingly important for the success of product lifecycle management in industry and complex supply chains. Semantic technologies are about to play a crucial role in this integrative process. However, cross-company data exchange requires mechanisms to enable fine-grained access control definition and enforcement, preventing unauthorized leakage of confidential data across company borders. Currently available semantic repositories are not sufficiently equipped to satisfy this important requirement. This paper presents an infrastructure for controlled sharing of semantic data between cooperating business partners. First, we motivate the need for access control in semantic data federations by a case study in the industrial service sector. Furthermore, we present an architecture for controlling access to semantic repositories that is based on our newly developed SemForce security service. Finally, we show the practical feasibility of this architecture by an implementation and several performance experiments. Amsterdam Elsevier 2012 11 Computers in industry : an international, application oriented research journal 63 9 930 940 10.1016/j.compind.2012.08.015 Institut für Informatik und Computational Science
OPUS4-36867 Wissenschaftlicher Artikel Weidlich, Matthias; Mendling, Jan; Weske, Mathias Efficient consistency measurement based on behavioral profiles of process models Engineering of process-driven business applications can be supported by process modeling efforts in order to bridge the gap between business requirements and system specifications. However, diverging purposes of business process modeling initiatives have led to significant problems in aligning related models at different abstract levels and different perspectives. Checking the consistency of such corresponding models is a major challenge for process modeling theory and practice. In this paper, we take the inappropriateness of existing strict notions of behavioral equivalence as a starting point. Our contribution is a concept called behavioral profile that captures the essential behavioral constraints of a process model. We show that these profiles can be computed efficiently, i.e., in cubic time for sound free-choice Petri nets w.r.t. their number of places and transitions. We use behavioral profiles for the definition of a formal notion of consistency which is less sensitive to model projections than common criteria of behavioral equivalence and allows for quantifying deviation in a metric way. The derivation of behavioral profiles and the calculation of a degree of consistency have been implemented to demonstrate the applicability of our approach. We also report the findings from checking consistency between partially overlapping models of the SAP reference model. Los Alamitos Inst. of Electr. and Electronics Engineers 2011 20 IEEE transactions on software engineering 37 3 410 429 10.1109/TSE.2010.96 Institut für Informatik und Computational Science
OPUS4-37528 Wissenschaftlicher Artikel Lucke, Ulrike; Rensing, Christoph A survey on pervasive education Researchers and developers worldwide have put their efforts into the design, development and use of information and communication technology to support teaching and learning. This research is driven by pedagogical as well as technological disciplines. The most challenging ideas are currently found in the application of mobile, ubiquitous, pervasive, contextualized and seamless technologies for education, which we shall refer to as pervasive education. This article provides a comprehensive overview of the existing work in this field and categorizes it with respect to educational settings. Using this approach, best practice solutions for certain educational settings and open questions for pervasive education are highlighted in order to inspire interested developers and educators. The work is assigned to different fields, identified by the main pervasive technologies used and the educational settings. Based on these assignments we identify areas within pervasive education that are currently disregarded or deemed challenging so that further research and development in these fields are stimulated in a trans-disciplinary approach. (C) 2013 Elsevier B.V. All rights reserved. Amsterdam Elsevier 2014 14 Pervasive and mobile computing 14 3 16 10.1016/j.pmcj.2013.12.001 Institut für Informatik und Computational Science
OPUS4-37529 Wissenschaftlicher Artikel Zender, Raphael; Metzler, Richard; Lucke, Ulrike FreshUP-A pervasive educational game for freshmen Students beginning their studies at university face manifold problems such as orientation in a new environment and organizing their courses. This article presents the implementation and successful empirical evaluation of the pervasive browser-based educational game "FreshUP", which aims at helping to overcome the initial difficulties of freshmen. In contrast to a conventional scavenger hunt, mobile pervasive games like FreshUP, bridging in-game and real world activities, have the potential to provide help in a motivating manner using new technology which is currently becoming more and more common. (C) 2013 Elsevier B.V. All rights reserved. Amsterdam Elsevier 2014 10 Pervasive and mobile computing 14 47 56 10.1016/j.pmcj.2013.09.003 Institut für Informatik und Computational Science
OPUS4-38036 Wissenschaftlicher Artikel Naujokat, Stefan; Neubauer, Johannes; Lamprecht, Anna-Lena; Steffen, Bernhard; Joerges, Sven; Margaria, Tiziana Simplicity-first model-based plug-in development In this article, we present our experience with over a decade of strict simplicity orientation in the development and evolution of plug-ins. The point of our approach is to enable our graphical modeling framework jABC to capture plug-in development in a domain-specific setting. The typically quite tedious and technical plug-in development is shifted this way from a programming task to the modeling level, where it can be mastered also by application experts without programming expertise. We show how the classical plug-in development profits from a systematic domain-specific API design and how the level of abstraction achieved this way can be further enhanced by defining adequate building blocks for high-level plug-in modeling. As the resulting plug-in models can be compiled and deployed automatically, our approach decomposes plug-in development into three phases where only the realization phase requires plug-in-specific effort. By using our modeling framework jABC, this effort boils down to graphical, tool-supported process modeling. Furthermore, we support the automatic completion of process sketches for executability. All this will be illustrated along the most recent plug-in-based evolution of the jABC framework, which witnessed quite some bootstrapping effects. Hoboken Wiley-Blackwell 2014 21 Software : practice & experience 44 3 277 297 10.1002/spe.2243 Institut für Informatik und Computational Science
OPUS4-38011 Wissenschaftlicher Artikel Troeger, Peter; Merzky, Andre Towards standardized job submission and control in infrastructure clouds The submission and management of computational jobs is a traditional part of utility computing environments. End users and developers of domain-specific software abstractions often have to deal with the heterogeneity of such batch processing systems. This lead to a number of application programming interface and job description standards in the past, which are implemented and established for cluster and Grid systems. With the recent rise of cloud computing as new utility computing paradigm, the standardized access to batch processing facilities operated on cloud resources becomes an important issue. Furthermore, the design of such a standard has to consider a tradeoff between feature completeness and the achievable level of interoperability. The article discusses this general challenge, and presents some existing standards with traditional cluster and Grid computing background that may be applicable to cloud environments. We present OCCI-DRMAA as one approach for standardized access to batch processing facilities hosted in a cloud. Dordrecht Springer 2014 15 Journal of grid computing 12 1 111 125 10.1007/s10723-013-9275-2 Institut für Informatik und Computational Science
OPUS4-35153 Wissenschaftlicher Artikel van Hooland, Seth; Verborgh, Ruben; De Wilde, Max; Hercher, Johannes; Mannens, Erik; Van de Walle, Rik Evaluating the success of vocabulary reconciliation for cultural heritage collections The concept of Linked Data has made its entrance in the cultural heritage sector due to its potential use for the integration of heterogeneous collections and deriving additional value out of existing metadata. However, practitioners and researchers alike need a better understanding of what outcome they can reasonably expect of the reconciliation process between their local metadata and established controlled vocabularies which are already a part of the Linked Data cloud. This paper offers an in-depth analysis of how a locally developed vocabulary can be successfully reconciled with the Library of Congress Subject Headings (LCSH) and the Arts and Architecture Thesaurus (AAT) through the help of a general-purpose tool for interactive data transformation (OpenRefine). Issues negatively affecting the reconciliation process are identified and solutions are proposed in order to derive maximum value from existing metadata and controlled vocabularies in an automated manner. Hoboken Wiley-Blackwell 2013 16 Journal of the American Society for Information Science and Technology 64 3 464 479 10.1002/asi.22763 Institut für Informatik und Computational Science
OPUS4-35866 Wissenschaftlicher Artikel Rabenalt, Thomas; Richter, Michael; Pöhl, Frank; Gössel, Michael Highly efficient test response compaction using a hierarchical x-masking technique This paper presents a highly effective compactor architecture for processing test responses with a high percentage of x-values. The key component is a hierarchical configurable masking register, which allows the compactor to dynamically adapt to and provide excellent performance over a wide range of x-densities. A major contribution of this paper is a technique that enables the efficient loading of the x-masking data into the masking logic in a parallel fashion using the scan chains. A method for eliminating the requirement for dedicated mask control signals using automated test equipment timing flexibility is also presented. The proposed compactor is especially suited to multisite testing. Experiments with industrial designs show that the proposed compactor enables compaction ratios exceeding 200x. Piscataway Inst. of Electr. and Electronics Engineers 2012 8 IEEE transactions on computer-aided design of integrated circuits and systems 31 6 950 957 10.1109/TCAD.2011.2181847 Institut für Informatik und Computational Science
OPUS4-35842 Wissenschaftlicher Artikel Srinivasan, K.; Senthilkumar, D. V.; Mohamed, I. Raja; Murali, K.; Lakshmanan, M.; Kurths, J. Anticipating, complete and lag synchronizations in RC phase-shift network based coupled Chua's circuits without delay We construct a new RC phase shift network based Chua's circuit, which exhibits a period-doubling bifurcation route to chaos. Using coupled versions of such a phase-shift network based Chua's oscillators, we describe a new method for achieving complete synchronization (CS), approximate lag synchronization (LS), and approximate anticipating synchronization (AS) without delay or parameter mismatch. Employing the Pecora and Carroll approach, chaos synchronization is achieved in coupled chaotic oscillators, where the drive system variables control the response system. As a result, AS or LS or CS is demonstrated without using a variable delay line both experimentally and numerically. Melville American Institute of Physics 2012 8 Chaos : an interdisciplinary journal of nonlinear science 22 2 10.1063/1.4711375 Institut für Informatik und Computational Science
OPUS4-36986 Wissenschaftlicher Artikel Gebser, Martin; Schaub, Torsten; Thiele, Sven; Veber, Philippe Detecting inconsistencies in large biological networks with answer set programming We introduce an approach to detecting inconsistencies in large biological networks by using answer set programming. To this end, we build upon a recently proposed notion of consistency between biochemical/genetic reactions and high-throughput profiles of cell activity. We then present an approach based on answer set programming to check the consistency of large-scale data sets. Moreover, we extend this methodology to provide explanations for inconsistencies by determining minimal representations of conflicts. In practice, this can be used to identify unreliable data or to indicate missing reactions. New York Cambridge Univ. Press 2011 38 Theory and practice of logic programming 11 5-6 323 360 10.1017/S1471068410000554 Institut für Informatik und Computational Science
OPUS4-35067 Wissenschaftlicher Artikel Kyprianidis, Jan Eric; Collomosse, John; Wang, Tinghuai; Isenberg, Tobias State of the "Art" a taxonomy of artistic stylization techniques for images and video This paper surveys the field of nonphotorealistic rendering (NPR), focusing on techniques for transforming 2D input (images and video) into artistically stylized renderings. We first present a taxonomy of the 2D NPR algorithms developed over the past two decades, structured according to the design characteristics and behavior of each technique. We then describe a chronology of development from the semiautomatic paint systems of the early nineties, through to the automated painterly rendering systems of the late nineties driven by image gradient analysis. Two complementary trends in the NPR literature are then addressed, with reference to our taxonomy. First, the fusion of higher level computer vision and NPR, illustrating the trends toward scene analysis to drive artistic abstraction and diversity of style. Second, the evolution of local processing approaches toward edge-aware filtering for real-time stylization of images and video. The survey then concludes with a discussion of open challenges for 2D NPR identified in recent NPR symposia, including topics such as user and aesthetic evaluation. Los Alamitos Inst. of Electr. and Electronics Engineers 2013 20 IEEE transactions on visualization and computer graphics 19 5 866 885 10.1109/TVCG.2012.160 Institut für Informatik und Computational Science
OPUS4-35093 Wissenschaftlicher Artikel Fabian, Benjamin; Kunz, Steffen; Müller, Sebastian; Günther, Oliver Secure federation of semantic information services fundamental challenge for product-lifecycle management in collaborative value networks is to utilize the vast amount of product information available from heterogeneous sources in order to improve business analytics, decision support, and processes. This becomes even more challenging if those sources are distributed across multiple organizations. Federations of semantic information services, combining service-orientation and semantic technologies, provide a promising solution for this problem. However, without proper measures to establish information security, companies will be reluctant to join an information federation, which could lead to serious adoption barriers. Following the design science paradigm, this paper presents general objectives and a process for designing a secure federation of semantic information services. Furthermore, new as well as established security measures are discussed. Here, our contributions include an access-control enforcement system for semantic information services and a process for modeling access-control policies across organizations. In addition, a comprehensive security architecture is presented. An implementation of the architecture in the context of an application scenario and several performance experiments demonstrate the practical viability of our approach. Amsterdam Elsevier 2013 14 Decision support systems : DSS ; the international journal 55 1 385 398 10.1016/j.dss.2012.05.049 Institut für Informatik und Computational Science
OPUS4-35974 Wissenschaftlicher Artikel Bordihn, Henning; Kutrib, Martin; Malcher, Andreas On the computational capacity of parallel communicating finite automata Systems of parallel finite automata communicating by states are investigated. We consider deterministic and nondeterministic devices and distinguish four working modes. It is known that systems in the most general mode are as powerful as one-way multi-head finite automata. Here we solve some open problems on the computational capacity of systems working in the remaining modes. In particular, it is shown that deterministic returning and non-returning devices are equivalent, and that there are languages which are accepted by deterministic returning and centralized systems but cannot be accepted by deterministic non-returning centralized systems. Furthermore, we show that nondeterministic systems are strictly more powerful than their deterministic variants in all the four working modes. Finally, incomparability with the classes of (deterministic) (linear) context-free languages as well as the Church-Rosser languages is derived. Singapore World Scientific 2012 20 International journal of foundations of computer science 23 3 713 732 10.1142/S0129054112500062 Institut für Informatik und Computational Science
OPUS4-36524 Wissenschaftlicher Artikel Gebser, Martin; Lee, Joohyung; Lierler, Yuliya On elementary loops of logic programs Using the notion of an elementary loop, Gebser and Schaub (2005. Proceedings of the Eighth International Conference on Logic Programming and Nonmonotonic Reasoning (LPNMR'05), 53-65) refined the theorem on loop formulas attributable to Lin and Zhao (2004) by considering loop formulas of elementary loops only. In this paper, we reformulate the definition of an elementary loop, extend it to disjunctive programs, and study several properties of elementary loops, including how maximal elementary loops are related to minimal unfounded sets. The results provide useful insights into the stable model semantics in terms of elementary loops. For a nondisjunctive program, using a graph-theoretic characterization of an elementary loop, we show that the problem of recognizing an elementary loop is tractable. On the other hand, we also show that the corresponding problem is coNP-complete for a disjunctive program. Based on the notion of an elementary loop, we present the class of Head-Elementary-loop-Free (HEF) programs, which strictly generalizes the class of Head-Cycle-Free (HCF) programs attributable to Ben-Eliyahu and Dechter (1994. Annals of Mathematics and Artificial Intelligence 12, 53-87). Like an Ha: program, an HEF program can be turned into an equivalent nondisjunctive program in polynomial time by shifting head atoms into the body. New York Cambridge Univ. Press 2011 36 Theory and practice of logic programming 11 2 953 988 10.1017/S1471068411000019 Institut für Informatik und Computational Science
OPUS4-36522 Wissenschaftlicher Artikel Bordihn, Henning; Kutrib, Martin; Malcher, Andreas Undecidability and hierarchy results for parallel communicating finite automata Parallel communicating finite automata (PCFAs) are systems of several finite state automata which process a common input string in a parallel way and are able to communicate by sending their states upon request. We consider deterministic and nondeterministic variants and distinguish four working modes. It is known that these systems in the most general mode are as powerful as one-way multi-head finite automata. It is additionally known that the number of heads corresponds to the number of automata in PCFAs in a constructive way. Thus, undecidability results as well as results on the hierarchies induced by the number of heads carry over from multi-head finite automata to PCFAs in the most general mode. Here, we complement these undecidability and hierarchy results also for the remaining working modes. In particular, we show that classical decidability questions are not semi-decidable for any type of PCFAs under consideration. Moreover, it is proven that the number of automata in the system induces infinite hierarchies for deterministic and nondeterministic PCFAs in three working modes. Singapore World Scientific 2011 16 International journal of foundations of computer science 22 7 1577 1592 10.1142/S0129054111008891 Institut für Informatik und Computational Science
OPUS4-36995 Wissenschaftlicher Artikel Bordihn, Henning; Holzer, Markus; Kutrib, Martin Decidability of operation problems for TOL languages and subclasses We investigate the decidability of the operation problem for TOL languages and subclasses. Fix an operation on formal languages. Given languages from the family considered (OL languages, TOL languages, or their propagating variants), is the application of this operation to the given languages still a language that belongs to the same language family? Observe, that all the Lindenmayer language families in question are anti-AFLs, that is, they are not closed under homomorphisms, inverse homomorphisms, intersection with regular languages, union, concatenation, and Kleene closure. Besides these classical operations we also consider intersection and substitution, since the language families under consideration are not closed under these operations, too. We show that for all of the above mentioned language operations, except for the Kleene closure, the corresponding operation problems of OL and TOL languages and their propagating variants are not even semidecidable. The situation changes for unary OL languages. In this case we prove that the operation problems with respect to Kleene star, complementation, and intersection with regular sets are decidable. San Diego Elsevier 2011 9 Information and computation 209 3 344 352 10.1016/j.ic.2010.11.008 Institut für Informatik und Computational Science
OPUS4-37028 Wissenschaftlicher Artikel Rabenalt, Thomas; Goessel, Michael; Leininger, Andreas Masking of X-Values by use of a hierarchically configurable register In this paper we consider masking of unknowns (X-values) for VLSI circuits. We present a new hierarchical method of X-masking which is a major improvement of the method proposed in [4], called WIDE1. By the method proposed, the number of observable scan cells is optimized and data volume for X-masking can be significantly reduced in comparison to WIDEL This is demonstrated for three industrial designs. In cases where all X-values have to be masked the novel approach is especially efficient. Dordrecht Springer 2011 11 Journal of electronic testing : theory and applications 27 1 31 41 10.1007/s10836-010-5179-2 Institut für Informatik und Computational Science
OPUS4-37029 Wissenschaftlicher Artikel Thon, Ingo; Landwehr, Niels; De Raedt, Luc Stochastic relational processes efficient inference and applications One of the goals of artificial intelligence is to develop agents that learn and act in complex environments. Realistic environments typically feature a variable number of objects, relations amongst them, and non-deterministic transition behavior. While standard probabilistic sequence models provide efficient inference and learning techniques for sequential data, they typically cannot fully capture the relational complexity. On the other hand, statistical relational learning techniques are often too inefficient to cope with complex sequential data. In this paper, we introduce a simple model that occupies an intermediate position in this expressiveness/efficiency trade-off. It is based on CP-logic (Causal Probabilistic Logic), an expressive probabilistic logic for modeling causality. However, by specializing CP-logic to represent a probability distribution over sequences of relational state descriptions and employing a Markov assumption, inference and learning become more tractable and effective. Specifically, we show how to solve part of the inference and learning problems directly at the first-order level, while transforming the remaining part into the problem of computing all satisfying assignments for a Boolean formula in a binary decision diagram. We experimentally validate that the resulting technique is able to handle probabilistic relational domains with a substantial number of objects and relations. Dordrecht Springer 2011 34 Machine learning 82 2 239 272 10.1007/s10994-010-5213-8 Institut für Informatik und Computational Science
OPUS4-37720 Wissenschaftlicher Artikel Hoos, Holger; Lindauer, Marius; Schaub, Torsten claspfolio 2 Building on the award-winning, portfolio-based ASP solver claspfolio, we present claspfolio 2, a modular and open solver architecture that integrates several different portfolio-based algorithm selection approaches and techniques. The claspfolio 2 solver framework supports various feature generators, solver selection approaches, solver portfolios, as well as solver-schedule-based pre-solving techniques. The default configuration of claspfolio 2 relies on a light-weight version of the ASP solver clasp to generate static and dynamic instance features. The flexible open design of claspfolio 2 is a distinguishing factor even beyond ASP. As such, it provides a unique framework for comparing and combining existing portfolio-based algorithm selection approaches and techniques in a single, unified framework. Taking advantage of this, we conducted an extensive experimental study to assess the impact of different feature sets, selection approaches and base solver portfolios. In addition to gaining substantial insights into the utility of the various approaches and techniques, we identified a default configuration of claspfolio 2 that achieves substantial performance gains not only over clasp's default configuration and the earlier version of claspfolio, but also over manually tuned configurations of clasp. New York Cambridge Univ. Press 2014 17 Theory and practice of logic programming 14 569 585 10.1017/S1471068414000210 Institut für Informatik und Computational Science
OPUS4-34949 Wissenschaftlicher Artikel Krasnova, Hanna; Veltri, Natasha F.; Spengler, Klaus; Günther, Oliver "Deal of the Day" Platforms what drives Consumer loyalty? "Deal of the Day" (DoD) platforms have quickly become popular by offering savings on local services, products and vacations. For merchants, these platforms represent a new marketing channel to advertise their products and services and attract new customers. DoD platform providers, however, struggle to maintaining a stable market share and profitability, because entry and switching costs are low. To sustain a competitive market position, DoD providers are looking for ways to build a loyal customer base. However, research examining the determinants of user loyalty in this novel context is scarce. To fill this gap, this study employs Grounded Theory methodology to develop a conceptual model of customer loyalty to a DoD provider. In the next step, qualitative insights are enriched and validated using quantitative data from a survey of 202 DoD users. The authors find that customer loyalty is in large part driven by monetary incentives, but can be eroded if impressions from merchant encounters are below expectations. In addition, enhancing the share of deals relevant for consumers, i.e. signal-to-noise ratio, and mitigating perceived risks of a transaction emerge as challenges. Beyond theoretical value, the results offer practical insights into how customer loyalty to a DoD provider can be promoted. Heidelberg Springer 2013 13 Business & information systems engineering : the international journal of Wirtschaftsinformatik 5 3 165 177 10.1007/s12599-013-0268-2 Institut für Informatik und Computational Science
OPUS4-34971 Wissenschaftlicher Artikel Delgrande, James; Schaub, Torsten; Tompits, Hans; Woltran, Stefan A model-theoretic approach to belief change in answer set programming We address the problem of belief change in (nonmonotonic) logic programming under answer set semantics. Our formal techniques are analogous to those of distance-based belief revision in propositional logic. In particular, we build upon the model theory of logic programs furnished by SE interpretations, where an SE interpretation is a model of a logic program in the same way that a classical interpretation is a model of a propositional formula. Hence we extend techniques from the area of belief revision based on distance between models to belief change in logic programs. We first consider belief revision: for logic programs P and Q, the goal is to determine a program R that corresponds to the revision of P by Q, denoted P * Q. We investigate several operators, including (logic program) expansion and two revision operators based on the distance between the SE models of logic programs. It proves to be the case that expansion is an interesting operator in its own right, unlike in classical belief revision where it is relatively uninteresting. Expansion and revision are shown to satisfy a suite of interesting properties; in particular, our revision operators satisfy all or nearly all of the AGM postulates for revision. We next consider approaches for merging a set of logic programs, P-1,...,P-n. Again, our formal techniques are based on notions of relative distance between the SE models of the logic programs. Two approaches are examined. The first informally selects for each program P-i those models of P-i that vary the least from models of the other programs. The second approach informally selects those models of a program P-0 that are closest to the models of programs P-1,...,P-n. In this case, P-0 can be thought of as a set of database integrity constraints. We examine these operators with regards to how they satisfy relevant postulate sets. Last, we present encodings for computing the revision as well as the merging of logic programs within the same logic programming framework. This gives rise to a direct implementation of our approach in terms of off-the-shelf answer set solvers. These encodings also reflect the fact that our change operators do not increase the complexity of the base formalism. New York Association for Computing Machinery 2013 46 ACM transactions on computational logic 14 2 10.1145/2480759.2480766 Institut für Informatik und Computational Science
OPUS4-34972 Wissenschaftlicher Artikel Gebser, Martin; Schaub, Torsten Tableau calculi for logic programs under answer set semantics We introduce formal proof systems based on tableau methods for analyzing computations in Answer Set Programming (ASP). Our approach furnishes fine-grained instruments for characterizing operations as well as strategies of ASP solvers. The granularity is detailed enough to capture a variety of propagation and choice methods of algorithms used for ASP solving, also incorporating SAT-based and conflict-driven learning approaches to some extent. This provides us with a uniform setting for identifying and comparing fundamental properties of ASP solving approaches. In particular, we investigate their proof complexities and show that the run-times of best-case computations can vary exponentially between different existing ASP solvers. Apart from providing a framework for comparing ASP solving approaches, our characterizations also contribute to their understanding by pinning down the constitutive atomic operations. Furthermore, our framework is flexible enough to integrate new inference patterns, and so to study their relation to existing ones. To this end, we generalize our approach and provide an extensible basis aiming at a modular incorporation of additional language constructs. This is exemplified by augmenting our basic tableau methods with cardinality constraints and disjunctions. New York Association for Computing Machinery 2013 40 ACM transactions on computational logic 14 2 10.1145/2480759.2480767 Institut für Informatik und Computational Science
OPUS4-36319 Wissenschaftlicher Artikel Paredes, E. G.; Boo, M.; Amor, M.; Bruguera, J. D.; Döllner, Jürgen Extended hybrid meshing algorithm for multiresolution terrain models Hybrid terrains are a convenient approach for the representation of digital terrain models, integrating heterogeneous data from different sources. In this article, we present a general, efficient scheme for achieving interactive level-of-detail rendering of hybrid terrain models, without the need for a costly preprocessing or resampling of the original data. The presented method works with hybrid digital terrains combining regular grid data and local high-resolution triangulated irregular networks. Since grid and triangulated irregular network data may belong to different datasets, a straightforward combination of both geometries would lead to meshes with holes and overlapping triangles. Our method generates a single multiresolution model integrating the different parts in a coherent way, by performing an adaptive tessellation of the region between their boundaries. Hence, our solution is one of the few existing approaches for integrating different multiresolution algorithms within the same terrain model, achieving a simple interactive rendering of complex hybrid terrains. Abingdon Routledge, Taylor & Francis Group 2012 23 International journal of geographical information science 26 5 771 793 10.1080/13658816.2011.615317 Institut für Informatik und Computational Science
OPUS4-36648 Wissenschaftlicher Artikel Jörges, Sven; Margaria, Tiziana; Steffen, Bernhard Assuring property conformance of code generators via model checking Automatic code generation is an essential cornerstone of today's model-driven approaches to software engineering. Thus a key requirement for the success of this technique is the reliability and correctness of code generators. This article describes how we employ standard model checking-based verification to check that code generator models developed within our code generation framework Genesys conform to (temporal) properties. Genesys is a graphical framework for the high-level construction of code generators on the basis of an extensible library of well-defined building blocks along the lines of the Extreme Model-Driven Development paradigm. We will illustrate our verification approach by examining complex constraints for code generators, which even span entire model hierarchies. We also show how this leads to a knowledge base of rules for code generators, which we constantly extend by e.g. combining constraints to bigger constraints, or by deriving common patterns from structurally similar constraints. In our experience, the development of code generators with Genesys boils down to re-instantiating patterns or slightly modifying the graphical process model, activities which are strongly supported by verification facilities presented in this article. New York Springer 2011 18 Formal aspects of computing : the international journal of formal methods 23 5 589 606 10.1007/s00165-010-0169-9 Institut für Informatik und Computational Science
OPUS4-37185 Wissenschaftlicher Artikel Cilia, Elisa; Landwehr, Niels; Passerini, Andrea Relational feature mining with hierarchical multitask kFOIL We introduce hierarchical kFOIL as a simple extension of the multitask kFOIL learning algorithm. The algorithm first learns a core logic representation common to all tasks, and then refines it by specialization on a per-task basis. The approach can be easily generalized to a deeper hierarchy of tasks. A task clustering algorithm is also proposed in order to automatically generate the task hierarchy. The approach is validated on problems of drug-resistance mutation prediction and protein structural classification. Experimental results show the advantage of the hierarchical version over both single and multi task alternatives and its potential usefulness in providing explanatory features for the domain. Task clustering allows to further improve performance when a deeper hierarchy is considered. Amsterdam IOS Press 2011 27 Fundamenta informaticae 113 2 151 177 10.3233/FI-2011-604 Institut für Informatik und Computational Science