TY  - JOUR
A1  - Delgrande, James
A1  - Schaub, Torsten H.
A1  - Tompits, Hans
A1  - Woltran, Stefan
T1  - A model-theoretic approach to belief change in answer set programming
JF  - ACM transactions on computational logic
N2  - 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.
KW  - Theory
KW  - Answer set programming
KW  - belief revision
KW  - belief merging
KW  - program encodings
KW  - strong equivalence
Y1  - 2013
U6  - https://doi.org/10.1145/2480759.2480766
SN  - 1529-3785
VL  - 14
IS  - 2
PB  - Association for Computing Machinery
CY  - New York
ER  - 
TY  - JOUR
A1  - Delikostidis, Ioannis
A1  - Engel, Juri
A1  - Retsios, Bas
A1  - van Elzakker, Corne P. J. M.
A1  - Kraak, Menno-Jan
A1  - Döllner, Jürgen Roland Friedrich
T1  - Increasing the usability of pedestrian navigation interfaces by means of landmark visibility analysis
JF  - The journal of navigation
N2  - 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.
KW  - Pedestrian navigation
KW  - Landmark visibility
KW  - User-centred design
KW  - Usability testing
Y1  - 2013
U6  - https://doi.org/10.1017/S0373463313000209
SN  - 0373-4633
VL  - 66
IS  - 4
SP  - 523
EP  - 537
PB  - Cambridge Univ. Press
CY  - New York
ER  - 
TY  - JOUR
A1  - Richter, Rico
A1  - Kyprianidis, Jan Eric
A1  - Döllner, Jürgen Roland Friedrich
T1  - Out-of-core GPU-based change detection in massive 3D point clouds
JF  - Transactions in GIS
N2  - If sites, cities, and landscapes are captured at different points in time using technology such as LiDAR, large collections of 3D point clouds result. Their efficient storage, processing, analysis, and presentation constitute a challenging task because of limited computation, memory, and time resources. In this work, we present an approach to detect changes in massive 3D point clouds based on an out-of-core spatial data structure that is designed to store data acquired at different points in time and to efficiently attribute 3D points with distance information. Based on this data structure, we present and evaluate different processing schemes optimized for performing the calculation on the CPU and GPU. In addition, we present a point-based rendering technique adapted for attributed 3D point clouds, to enable effective out-of-core real-time visualization of the computation results. Our approach enables conclusions to be drawn about temporal changes in large highly accurate 3D geodata sets of a captured area at reasonable preprocessing and rendering times. We evaluate our approach with two data sets from different points in time for the urban area of a city, describe its characteristics, and report on applications.
Y1  - 2013
U6  - https://doi.org/10.1111/j.1467-9671.2012.01362.x
SN  - 1361-1682
VL  - 17
IS  - 5
SP  - 724
EP  - 741
PB  - Wiley-Blackwell
CY  - Hoboken
ER  - 
TY  - JOUR
A1  - Hilse, Michael
A1  - Lucke, Ulrike
T1  - eLiS − E-Learning in Studienbereichen
JF  - E-Learning Symposium 2012 : Aktuelle Anwendungen, innovative Prozesse und neueste Ergebnisse aus der E-Learning-Praxis ; Potsdam, 17. November 2012
N2  - Deutsche Universitäten erweitern ihre E-Learning-Angebote als Service für die Studierenden und Lehrenden. Diese sind je nach Fakultät unterschiedlich ausgeprägt. Dieser Artikel zeigt, wie durch technische Erweiterung der Infrastruktur, einer Anpassung der Organisationsstruktur und einer gezielten Inhaltsentwicklung eine durchgängige und personalisierbare Lehr- und Lernumgebung (Personal Learning Environment, PLE) geschaffen und damit die Akzeptanz bei den Lehrenden und Studierenden für E-Learning erhöht werden kann. Aus der vorausgehenden, systematischen Anforderungsanalyse können Kennzahlen für die Qualitätssicherung von E-Learning-Angeboten abgeleitet werden.
Y1  - 2013
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-442275
SP  - 73
EP  - 75
PB  - Universitätsverlag Potsdam
CY  - Potsdam
ER  - 
TY  - JOUR
A1  - Steinert, Bastian
A1  - Cassou, Damien
A1  - Hirschfeld, Robert
T1  - CoExist overcoming aversion to change preserving immediate access to source code and run-time information of previous development states
JF  - ACM SIGPLAN notices
N2  - 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.
KW  - Design
KW  - Experimentation
KW  - Human Factors
KW  - Continuous Testing
KW  - Continuous Versioning
KW  - Debugging
KW  - Evolution
KW  - Explore-first Programming
KW  - Fault Localization
KW  - Prototyping
Y1  - 2013
U6  - https://doi.org/10.1145/2480360.2384591
SN  - 0362-1340
VL  - 48
IS  - 2
SP  - 107
EP  - 117
PB  - Association for Computing Machinery
CY  - New York
ER  - 
TY  - JOUR
A1  - van Hooland, Seth
A1  - Verborgh, Ruben
A1  - De Wilde, Max
A1  - Hercher, Johannes
A1  - Mannens, Erik
A1  - Van de Walle, Rik
T1  - Evaluating the success of vocabulary reconciliation for cultural heritage collections
JF  - Journal of the American Society for Information Science and Technology
N2  - 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.
KW  - semantic web
KW  - metadata
KW  - controlled vocabularies
Y1  - 2013
U6  - https://doi.org/10.1002/asi.22763
SN  - 1532-2882
VL  - 64
IS  - 3
SP  - 464
EP  - 479
PB  - Wiley-Blackwell
CY  - Hoboken
ER  - 
TY  - JOUR
A1  - Montavon, Gregoire
A1  - Braun, Mikio L.
A1  - Krüger, Tammo
A1  - Müller, Klaus-Robert
T1  - Analyzing local structure in Kernel-Based learning
JF  - IEEE signal processing magazine
Y1  - 2013
U6  - https://doi.org/10.1109/MSP.2013.2249294
SN  - 1053-5888
VL  - 30
IS  - 4
SP  - 62
EP  - 74
PB  - Inst. of Electr. and Electronics Engineers
CY  - Piscataway
ER  - 
TY  - JOUR
A1  - Gebser, Martin
A1  - Schaub, Torsten H.
T1  - Tableau calculi for logic programs under answer set semantics
JF  - ACM transactions on computational logic
N2  - 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.
KW  - Theory
KW  - Answer Set Programming
KW  - tableau calculi
KW  - proof complexity
Y1  - 2013
U6  - https://doi.org/10.1145/2480759.2480767
SN  - 1529-3785
VL  - 14
IS  - 2
PB  - Association for Computing Machinery
CY  - New York
ER  - 
TY  - JOUR
A1  - Guziolowski, Carito
A1  - Videla, Santiago
A1  - Eduati, Federica
A1  - Thiele, Sven
A1  - Cokelaer, Thomas
A1  - Siegel, Anne
A1  - Saez-Rodriguez, Julio
T1  - Exhaustively characterizing feasible logic models of a signaling network using Answer Set Programming
JF  - Bioinformatics
N2  - Motivation: Logic modeling is a useful tool to study signal transduction across multiple pathways. Logic models can be generated by training a network containing the prior knowledge to phospho-proteomics data. The training can be performed using stochastic optimization procedures, but these are unable to guarantee a global optima or to report the complete family of feasible models. This, however, is essential to provide precise insight in the mechanisms underlaying signal transduction and generate reliable predictions.
 Results: We propose the use of Answer Set Programming to explore exhaustively the space of feasible logic models. Toward this end, we have developed caspo, an open-source Python package that provides a powerful platform to learn and characterize logic models by leveraging the rich modeling language and solving technologies of Answer Set Programming. We illustrate the usefulness of caspo by revisiting a model of pro-growth and inflammatory pathways in liver cells. We show that, if experimental error is taken into account, there are thousands (11 700) of models compatible with the data. Despite the large number, we can extract structural features from the models, such as links that are always (or never) present or modules that appear in a mutual exclusive fashion. To further characterize this family of models, we investigate the input-output behavior of the models. We find 91 behaviors across the 11 700 models and we suggest new experiments to discriminate among them. Our results underscore the importance of characterizing in a global and exhaustive manner the family of feasible models, with important implications for experimental design.
Y1  - 2013
U6  - https://doi.org/10.1093/bioinformatics/btt393
SN  - 1367-4803
VL  - 29
IS  - 18
SP  - 2320
EP  - 2326
PB  - Oxford Univ. Press
CY  - Oxford
ER  - 
TY  - JOUR
A1  - Floyd, Barry D.
A1  - Bosselmann, Steve
T1  - ITSy-simplicity research in information and communication technology
JF  - Computer : innovative technology for computer professionals
N2  - Basic to information and communication technology design, simplicity as a driving concept receives little formal attention from the ICT community. A recent literature review and survey of scholars, researchers, and practitioners conducted through the Information Technology Simply Works (ITSy) European Support Action reveals key findings about current perceptions of and future directions for simplicity in ICT.
Y1  - 2013
SN  - 0018-9162
SN  - 1558-0814
VL  - 46
IS  - 11
SP  - 26
EP  - 32
PB  - Inst. of Electr. and Electronics Engineers
CY  - Los Alamitos
ER  - 
TY  - JOUR
A1  - Kaminski, Roland
A1  - Schaub, Torsten H.
A1  - Siegel, Anne
A1  - Videla, Santiago
T1  - Minimal intervention strategies in logical signaling networks with ASP
JF  - Theory and practice of logic programming
N2  - 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.
Y1  - 2013
U6  - https://doi.org/10.1017/S1471068413000422
SN  - 1471-0684
VL  - 13
SP  - 675
EP  - 690
PB  - Cambridge Univ. Press
CY  - New York
ER  - 
TY  - JOUR
A1  - Kyprianidis, Jan Eric
A1  - Collomosse, John
A1  - Wang, Tinghuai
A1  - Isenberg, Tobias
T1  - State of the "Art" a taxonomy of artistic stylization techniques for images and video
JF  - IEEE transactions on visualization and computer graphics
N2  - 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.
KW  - Image and video stylization
KW  - nonphotorealistic rendering (NPR)
KW  - artistic rendering
Y1  - 2013
U6  - https://doi.org/10.1109/TVCG.2012.160
SN  - 1077-2626
VL  - 19
IS  - 5
SP  - 866
EP  - 885
PB  - Inst. of Electr. and Electronics Engineers
CY  - Los Alamitos
ER  - 
TY  - JOUR
A1  - Fabian, Benjamin
A1  - Kunz, Steffen
A1  - Müller, Sebastian
A1  - Günther, Oliver
T1  - Secure federation of semantic information services
JF  - Decision support systems : DSS ; the international journal
N2  - 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.
KW  - Information federation
KW  - Service orientation
KW  - Semantic web
KW  - Information security
Y1  - 2013
U6  - https://doi.org/10.1016/j.dss.2012.05.049
SN  - 0167-9236
VL  - 55
IS  - 1
SP  - 385
EP  - 398
PB  - Elsevier
CY  - Amsterdam
ER  - 
TY  - JOUR
A1  - Krasnova, Hanna
A1  - Veltri, Natasha F.
A1  - Spengler, Klaus
A1  - Günther, Oliver
T1  - "Deal of the Day" Platforms what drives Consumer loyalty?
JF  - Business & information systems engineering : the international journal of Wirtschaftsinformatik
N2  - "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.
KW  - Deal of the Day
KW  - Loyalty
KW  - Grounded theory
KW  - Structural equation modeling
Y1  - 2013
U6  - https://doi.org/10.1007/s12599-013-0268-2
SN  - 1867-0202
VL  - 5
IS  - 3
SP  - 165
EP  - 177
PB  - Springer
CY  - Heidelberg
ER  - 
TY  - JOUR
A1  - Kiertscher, Simon
A1  - Zinke, Jörg
A1  - Schnor, Bettina
T1  - CHERUB power consumption aware cluster resource management
JF  - Cluster computing : the journal of networks, software tools and applications
N2  - 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.
KW  - Green computing
KW  - Cluster computing
Y1  - 2013
U6  - https://doi.org/10.1007/s10586-011-0176-5
SN  - 1386-7857
VL  - 16
IS  - 1
SP  - 55
EP  - 63
PB  - Springer
CY  - New York
ER  - 
TY  - JOUR
A1  - Sawade, Christoph
A1  - Bickel, Steffen
A1  - von Oertzen, Timo
A1  - Scheffer, Tobias
A1  - Landwehr, Niels
T1  - Active evaluation of ranking functions based on graded relevance
JF  - Machine learning
N2  - 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.
KW  - Information retrieval
KW  - Ranking
KW  - Active evaluation
Y1  - 2013
U6  - https://doi.org/10.1007/s10994-013-5372-5
SN  - 0885-6125
VL  - 92
IS  - 1
SP  - 41
EP  - 64
PB  - Springer
CY  - Dordrecht
ER  - 
TY  - JOUR
A1  - Banbara, Mutsunori
A1  - Soh, Takehide
A1  - Tamura, Naoyuki
A1  - Inoue, Katsumi
A1  - Schaub, Torsten H.
T1  - Answer set programming as a modeling language for course timetabling
JF  - Theory and practice of logic programming
N2  - 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.
KW  - answer set programming
KW  - educational timetabling
KW  - course timetabling
Y1  - 2013
U6  - https://doi.org/10.1017/S1471068413000495
SN  - 1471-0684
VL  - 13
IS  - 2
SP  - 783
EP  - 798
PB  - Cambridge Univ. Press
CY  - New York
ER  -