@article{GlanderDoellner2009, author = {Glander, Tassilo and D{\"o}llner, J{\"u}rgen Roland Friedrich}, title = {Abstract representations for interactive visualization of virtual 3D city models}, issn = {0198-9715}, doi = {10.1016/j.compenvurbsys.2009.07.003}, year = {2009}, abstract = {Virtual 3D city models increasingly cover whole city areas; hence, the perception of complex urban structures becomes increasingly difficult. Using abstract visualization, complexity of these models can be hidden where its visibility is unnecessary, while important features are maintained and highlighted for better comprehension and communication. We present a technique to automatically generalize a given virtual 3D city model consisting of building models, an infrastructure network and optional land coverage data; this technique creates several representations of increasing levels of abstraction. Using the infrastructure network, our technique groups building models and replaces them with cell blocks, while preserving local landmarks. By computing a landmark hierarchy, we reduce the set of initial landmarks in a spatially balanced manner for use in higher levels of abstraction. In four application examples, we demonstrate smooth visualization of transitions between precomputed representations; dynamic landmark highlighting according to virtual camera distance; an implementation of a cognitively enhanced route representation, and generalization lenses to combine precomputed representations in focus + context visualization.}, language = {en} } @article{DeckerKoppLeymannetal.2009, author = {Decker, Gero and Kopp, Oliver and Leymann, Frank and Weske, Mathias}, title = {Interacting services : from specification to execution}, issn = {0169-023X}, doi = {10.1016/j.datak.2009.04.003}, year = {2009}, abstract = {Interacting services play a key role to realize business process integration among different business partners by means of electronic message exchange. In order to provide seamless integration of these services, the messages exchanged as well as their dependencies must be well-defined. Service choreographies are a means to describe the allowed conversations. This article presents a requirements framework for service choreography languages, along which existing choreography languages are assessed. The requirements framework provides the basis for introducing the language BPEL4Chor, which extends the industry standard WS-BPEL with choreography-specific concepts. A validation is provided and integration with executable service orchestrations is discussed.}, language = {en} } @article{DeckerMendling2009, author = {Decker, Gero and Mendling, Jan}, title = {Process instantiation}, issn = {0169-023X}, doi = {10.1016/j.datak.2009.02.013}, year = {2009}, abstract = {Although several process modeling languages allow one to specify processes with multiple start elements, the precise semantics of such models are often unclear, both from a pragmatic and from a theoretical point of view. This paper addresses the lack of research on this problem and introduces the CASU framework (from Creation, Activation, subscription, Unsubscription). The contribution of this framework is a systematic description of design alternatives for the specification of instantiation semantics of process modeling languages. We classify six prominent languages by the help of this framework. We validate the relevance of the CASU framework through empirical investigations involving a large set of process models from practice. Our work provides the basis for the design of new correctness criteria as well as for the formalization of Event-driven Process Chains (EPCs) and extension of the Business Process Modeling Notation (BPMN). It complements research such as the workflow patterns.}, language = {en} } @article{TroegerPolze2009, author = {Troeger, Peter and Polze, Andreas}, title = {Object and process migration in .NET}, issn = {0267-6192}, year = {2009}, abstract = {Many of today's distributed computing systems in the field do not Support the migration of execution entities among computing nodes (luring runtime. The relatively static association between units of processing and computing nodes makes it difficult to implement fault-tolerant behavior or load-balancing schemes. The concept of code migration may provide a solution to the above-mentioned problems. it can be defined as the movement of processes, objects, or components from one computing node to another during system runtime in a distributed environment. With the advent of the virtual machine-based NET framework, many of the cross-language heterogeneity issues have been resolved. With the commercial implementation, the shared source "Rotor", and the open-source "Mono" implementation on hand, we have focused on cross-operating system heterogeneity issues and present interoperability and migration schemes for applications distributed over different operating systems (namely Linux and Windows 2000) as well as various NET implementations. Within this paper, we describe the integration of a migration facility with the hell) of Aspect- Oriented Programming (AOP) into the NET framework. AOP is interesting as it addresses non-functional system properties on the middleware level, without the need to manipulate lower system layers like the operating system itself. Most features required to implement object or process migration (such as reflection mechanisms or a machine-independent executable format) are already present in the NET frameworks, so the integration of such a concept is a natural extension of the system capabilities. We have implemented several proof-of-concept applications for different use case scenarios. The paper contains an experimental evaluation of the performance impact of object migration in context of those applications.}, language = {en} } @article{WistWollowskiSchaeferetal.2009, author = {Wist, Dominic and Wollowski, Ralf and Schaefer, Mark and Vogler, Walter}, title = {Avoiding irreducible CSC conflicts by internal communication}, issn = {0169-2968}, doi = {10.3233/Fi-2009-140}, year = {2009}, abstract = {Resynthesis of handshake specifications obtained e. g. from BALSA or TANGRAM with speed-independent logic synthesis from STGs is a promising approach. To deal with state-space explosion, we suggested STG decomposition; a problem is that decomposition can lead to irreducible CSC conflicts. Here, we present a new approach to solve such conflicts by introducing internal communication between the components. We give some first, very encouraging results for very large STGs concerning synthesis time and circuit area.}, language = {en} } @article{KhomenkoSchaeferVogleretal.2009, author = {Khomenko, Victor and Sch{\"a}fer, Mark and Vogler, Walter and Wollowski, Ralf}, title = {STG decomposition strategies in combination with unfolding}, issn = {0001-5903}, doi = {10.1007/s00236-009-0102-y}, year = {2009}, abstract = {For synthesising efficient asynchronous circuits one has to deal with the state space explosion problem. In order to alleviate this problem one can decompose the STG into smaller components. This paper deals with the decomposition method of Vogler and Wollowski and introduces several strategies for its efficient implementations. Furthermore, this approach is combined with another method to alleviate state space explosion, which is based on Petri net unfoldings. The developed algorithms are compared by means of benchmark examples, and the experimental results show significant improvement in terms of memory usage and runtime compared with other existing methods.}, language = {en} } @article{HauptAdamsTimbermontetal.2009, author = {Haupt, Michael and Adams, Bram and Timbermont, Stijn and Gibbs, Celina and Coady, Yvonne and Hirschfeld, Robert}, title = {Disentangling virtual machine architecture}, issn = {1751-8806}, doi = {10.1049/iet-sen.2007.0121}, year = {2009}, abstract = {Virtual machine (VM) implementations are made of intricately intertwined subsystems, interacting largely through implicit dependencies. As the degree of crosscutting present in VMs is very high, VM implementations exhibit significant internal complexity. This study proposes an architecture approach for VMs that regards a VM as a composite of service modules coordinated through explicit bidirectional interfaces. Aspect-oriented programming techniques are used to establish these interfaces, to coordinate module interaction, and to declaratively express concrete VM architectures. A VM architecture description language is presented in a case study, illustrating the application of the proposed architectural principles.}, language = {en} } @article{GieseWagner2009, author = {Giese, Holger and Wagner, Robert}, title = {From model transformation to incremental bidirectional model synchronization}, issn = {1619-1366}, doi = {10.1007/s10270-008-0089-9}, year = {2009}, abstract = {The model-driven software development paradigm requires that appropriate model transformations are applicable in different stages of the development process. The transformations have to consistently propagate changes between the different involved models and thus ensure a proper model synchronization. However, most approaches today do not fully support the requirements for model synchronization and focus only on classical one-way batch-oriented transformations. In this paper, we present our approach for an incremental model transformation which supports model synchronization. Our approach employs the visual, formal, and bidirectional transformation technique of triple graph grammars. Using this declarative specification formalism, we focus on the efficient execution of the transformation rules and how to achieve an incremental model transformation for synchronization purposes. We present an evaluation of our approach and demonstrate that due to the speedup for the incremental processing in the average case even larger models can be tackled.}, language = {en} } @article{SeibelNeumannGiese2010, author = {Seibel, Andreas and Neumann, Stefan and Giese, Holger}, title = {Dynamic hierarchical mega models : comprehensive traceability and its efficient maintenance}, issn = {1619-1366}, doi = {10.1007/s10270-009-0146-z}, year = {2010}, abstract = {In the world of model-driven engineering (MDE) support for traceability and maintenance of traceability information is essential. On the one hand, classical traceability approaches for MDE address this need by supporting automated creation of traceability information on the model element level. On the other hand, global model management approaches manually capture traceability information on the model level. However, there is currently no approach that supports comprehensive traceability, comprising traceability information on both levels, and efficient maintenance of traceability information, which requires a high-degree of automation and scalability. In this article, we present a comprehensive traceability approach that combines classical traceability approaches for MDE and global model management in form of dynamic hierarchical mega models. We further integrate efficient maintenance of traceability information based on top of dynamic hierarchical mega models. The proposed approach is further outlined by using an industrial case study and by presenting an implementation of the concepts in form of a prototype.}, language = {en} } @article{HildebrandtDoellner2010, author = {Hildebrandt, Dieter and D{\"o}llner, J{\"u}rgen}, title = {Service-oriented, standards-based 3D geovisualization : potential and challenges}, issn = {0198-9715}, doi = {10.1016/j.compenvurbsys.2010.05.003}, year = {2010}, abstract = {The application of the architectural concept of service-oriented architectures (SOA) in combination with open standards when building distributed, 3D geovisualization systems offers the potential to cover and take advantage of the opportunities and demands created by the rise of ubiquitous computer networks and the Internet as well as to overcome prevalent interoperability barriers. In this paper, based on a literature study and our own experiences, we discuss the potential and challenges that arise when building standards-based, distributed systems according to the SOA paradigm for 3D geovisualization, with a particular focus on 3D geovirtual environments and virtual 3D city models. First, we briefly introduce fundamentals of the SOA paradigm, identify requirements for service-oriented 3D geovisualization systems, and present an architectural framework that relates SOA concepts, geovisualization concepts, and standardization proposals by the Open Geospatial Consortium in a common frame of reference. Next, we discuss the potential and challenges driven by the SOA paradigm on four different levels of abstraction, namely service fundamentals, service composition, interaction services, performance, and overarching aspects, and we discuss those driven by standardization. We further exemplify and substantiate the discussion in the scope of a case study and the image-based provisioning of and interaction with visual representations of remote virtual 3D city models.}, language = {en} } @article{KuehneHuitemaCarle2011, author = {K{\"u}hne, Ralph and Huitema, George and Carle, Georg}, title = {A simple distributed mechanism for accounting system self-configuration in next-generation charging and billing}, series = {Computer communications}, volume = {34}, journal = {Computer communications}, number = {7}, publisher = {Elsevier}, address = {Amsterdam}, issn = {0140-3664}, doi = {10.1016/j.comcom.2010.10.012}, pages = {898 -- 920}, year = {2011}, abstract = {Modern communication systems are becoming increasingly dynamic and complex. In this article a novel mechanism for next generation charging and billing is presented that enables self-configurability for accounting systems consisting of heterogeneous components. The mechanism is required to be simple, effective, efficient, scalable and fault-tolerant. Based on simulation results it is shown that the proposed simple distributed mechanism is competitive with usual cost-based or random mechanisms under realistic assumptions and up to non-extreme workload situations as well as fulfilling the posed requirements.}, language = {en} } @article{BogPlattnerZeier2011, author = {Bog, Anja and Plattner, Hasso and Zeier, Alexander}, title = {A mixed transaction processing and operational reporting benchmark}, series = {Information systems frontiers}, volume = {13}, journal = {Information systems frontiers}, number = {3}, publisher = {Springer}, address = {Dordrecht}, issn = {1387-3326}, doi = {10.1007/s10796-010-9283-8}, pages = {321 -- 335}, year = {2011}, abstract = {The importance of reporting is ever increasing in today's fast-paced market environments and the availability of up-to-date information for reporting has become indispensable. Current reporting systems are separated from the online transaction processing systems (OLTP) with periodic updates pushed in. A pre-defined and aggregated subset of the OLTP data, however, does not provide the flexibility, detail, and timeliness needed for today's operational reporting. As technology advances, this separation has to be re-evaluated and means to study and evaluate new trends in data storage management have to be provided. This article proposes a benchmark for combined OLTP and operational reporting, providing means to evaluate the performance of enterprise data management systems for mixed workloads of OLTP and operational reporting queries. Such systems offer up-to-date information and the flexibility of the entire data set for reporting. We describe how the benchmark provokes the conflicts that are the reason for separating the two workloads on different systems. In this article, we introduce the concepts, logical data schema, transactions and queries of the benchmark, which are entirely based on the original data sets and real workloads of existing, globally operating enterprises.}, language = {en} } @article{LinckeAppeltauerSteinertetal.2011, author = {Lincke, Jens and Appeltauer, Malte and Steinert, Bastian and Hirschfeld, Robert}, title = {An open implementation for context-oriented layer composition in ContextJS}, series = {Science of computer programming}, volume = {76}, journal = {Science of computer programming}, number = {12}, publisher = {Elsevier}, address = {Amsterdam}, issn = {0167-6423}, doi = {10.1016/j.scico.2010.11.013}, pages = {1194 -- 1209}, year = {2011}, abstract = {Context-oriented programming (COP) provides dedicated support for defining and composing variations to a basic program behavior. A variation, which is defined within a layer, can be de-/activated for the dynamic extent of a code block. While this mechanism allows for control flow-specific scoping, expressing behavior adaptations can demand alternative scopes. For instance, adaptations can depend on dynamic object structure rather than control flow. We present scenarios for behavior adaptation and identify the need for new scoping mechanisms. The increasing number of scoping mechanisms calls for new language abstractions representing them. We suggest to open the implementation of scoping mechanisms so that developers can extend the COP language core according to their specific needs. Our open implementation moves layer composition into objects to be affected and with that closer to the method dispatch to be changed. We discuss the implementation of established COP scoping mechanisms using our approach and present new scoping mechanisms developed for our enhancements to Lively Kernel.}, language = {en} } @article{HenklerOberthuerGieseetal.2011, author = {Henkler, Stefan and Oberthuer, Simon and Giese, Holger and Seibel, Andreas}, title = {Model-driven runtime resource predictions for advanced mechatronic systems with dynamic data structures}, series = {Computer systems science and engineering}, volume = {26}, journal = {Computer systems science and engineering}, number = {6}, publisher = {IOP Publ. Ltd.}, address = {Leicester}, issn = {0267-6192}, pages = {505 -- 518}, year = {2011}, abstract = {The next generation of advanced mechatronic systems is expected to enhance their functionality and improve their performance by context-dependent behavior. Therefore, these systems require to represent information about their complex environment and changing sets of collaboration partners internally. This requirement is in contrast to the usually assumed static structures of embedded systems. In this paper, we present a model-driven approach which overcomes this situation by supporting dynamic data structures while still guaranteeing that valid worst-case execution times can be derived. It supports a flexible resource manager which avoids to operate with the prohibitive coarse worst-case boundaries but instead supports to run applications in different profiles which guarantee different resource requirements and put unused resources in a profile at other applications' disposal. By supporting the proper estimation of worst case execution time (WCET) and worst case number of iteration (WCNI) at runtime, we can further support to create new profiles, add or remove them at runtime in order to minimize the over-approximation of the resource consumption resulting from the dynamic data structures required for the outlined class of advanced systems.}, language = {en} } @article{DeckerWeske2011, author = {Decker, Gero and Weske, Mathias}, title = {Interaction-centric modeling of process choreographies}, series = {Information systems}, volume = {36}, journal = {Information systems}, number = {2}, publisher = {Elsevier}, address = {Oxford}, issn = {0306-4379}, doi = {10.1016/j.is.2010.06.005}, pages = {292 -- 312}, year = {2011}, abstract = {With the rise of electronic integration between organizations, the need for a precise specification of interaction behavior increases. Information systems, replacing interaction previously carried out by humans via phone, faxes and emails, require a precise specification for handling all possible situations. Such interaction behavior is described in process choreographies. While many proposals for choreography languages have already been made, most of them fall into the category of interconnection models, where the observable behavior of the different partners is described and then related via message flow. As this article will show, this modeling approach fails to support fundamental design principles of choreographies and typically leads to modeling errors. This motivates an alternative modeling style, namely interaction modeling, for overcoming these limitations. While the main concepts are independent of a concrete modeling language, iBPMN is introduced as novel interaction modeling language. Formal execution semantics are provided and a comprehensive toolset implementing the approach is presented.}, language = {en} } @article{AwadWeidlichWeske2011, author = {Awad, Ahmed Mahmoud Hany Aly and Weidlich, Matthias and Weske, Mathias}, title = {Visually specifying compliance rules and explaining their violations for business processes}, series = {Journal of visual languages and computing}, volume = {22}, journal = {Journal of visual languages and computing}, number = {1}, publisher = {Elsevier}, address = {London}, issn = {1045-926X}, doi = {10.1016/j.jvlc.2010.11.002}, pages = {30 -- 55}, year = {2011}, abstract = {A business process is a set of steps designed to be executed in a certain order to achieve a business value. Such processes are often driven by and documented using process models. Nowadays, process models are also applied to drive process execution. Thus, correctness of business process models is a must. Much of the work has been devoted to check general, domain-independent correctness criteria, such as soundness. However, business processes must also adhere to and show compliance with various regulations and constraints, the so-called compliance requirements. These are domain-dependent requirements. In many situations, verifying compliance on a model level is of great value, since violations can be resolved in an early stage prior to execution. However, this calls for using formal verification techniques, e.g., model checking, that are too complex for business experts to apply. In this paper, we utilize a visual language. BPMN-Q to express compliance requirements visually in a way similar to that used by business experts to build process models. Still, using a pattern based approach, each BPMN-Qgraph has a formal temporal logic expression in computational tree logic (CTL). Moreover, the user is able to express constraints, i.e., compliance rules, regarding control flow and data flow aspects. In order to provide valuable feedback to a user in case of violations, we depend on temporal logic querying approaches as well as BPMN-Q to visually highlight paths in a process model whose execution causes violations.}, language = {en} } @article{WeidlichPolyvyanyyMendlingetal.2011, author = {Weidlich, Matthias and Polyvyanyy, Artem and Mendling, Jan and Weske, Mathias}, title = {Causal behavioural profiles - efficient computation, applications, and evaluation}, series = {Fundamenta informaticae}, volume = {113}, journal = {Fundamenta informaticae}, number = {3-4}, publisher = {IOS Press}, address = {Amsterdam}, issn = {0169-2968}, doi = {10.3233/FI-2011-614}, pages = {399 -- 435}, year = {2011}, abstract = {Analysis of behavioural consistency is an important aspect of software engineering. In process and service management, consistency verification of behavioural models has manifold applications. For instance, a business process model used as system specification and a corresponding workflow model used as implementation have to be consistent. Another example would be the analysis to what degree a process log of executed business operations is consistent with the corresponding normative process model. Typically, existing notions of behaviour equivalence, such as bisimulation and trace equivalence, are applied as consistency notions. Still, these notions are exponential in computation and yield a Boolean result. In many cases, however, a quantification of behavioural deviation is needed along with concepts to isolate the source of deviation. In this article, we propose causal behavioural profiles as the basis for a consistency notion. These profiles capture essential behavioural information, such as order, exclusiveness, and causality between pairs of activities of a process model. Consistency based on these profiles is weaker than trace equivalence, but can be computed efficiently for a broad class of models. In this article, we introduce techniques for the computation of causal behavioural profiles using structural decomposition techniques for sound free-choice workflow systems if unstructured net fragments are acyclic or can be traced back to S-or T-nets. We also elaborate on the findings of applying our technique to three industry model collections.}, language = {en} } @article{WeidlichPolyvyanyyDesaietal.2011, author = {Weidlich, Matthias and Polyvyanyy, Artem and Desai, Nirmit and Mendling, Jan and Weske, Mathias}, title = {Process compliance analysis based on behavioural profiles}, series = {Information systems}, volume = {36}, journal = {Information systems}, number = {7}, publisher = {Elsevier}, address = {Oxford}, issn = {0306-4379}, doi = {10.1016/j.is.2011.04.002}, pages = {1009 -- 1025}, year = {2011}, abstract = {Process compliance measurement is getting increasing attention in companies due to stricter legal requirements and market pressure for operational excellence. In order to judge on compliance of the business processing, the degree of behavioural deviation of a case, i.e., an observed execution sequence, is quantified with respect to a process model (referred to as fitness, or recall). Recently, different compliance measures have been proposed. Still, nearly all of them are grounded on state-based techniques and the trace equivalence criterion, in particular. As a consequence, these approaches have to deal with the state explosion problem. In this paper, we argue that a behavioural abstraction may be leveraged to measure the compliance of a process log - a collection of cases. To this end, we utilise causal behavioural profiles that capture the behavioural characteristics of process models and cases, and can be computed efficiently. We propose different compliance measures based on these profiles, discuss the impact of noise in process logs on our measures, and show how diagnostic information on non-compliance is derived. As a validation, we report on findings of applying our approach in a case study with an international service provider.}, language = {en} } @article{LaueAwad2011, author = {Laue, Ralf and Awad, Ahmed Mahmoud Hany Aly}, title = {Visual suggestions for improvements in business process diagrams}, series = {Journal of visual languages and computing}, volume = {22}, journal = {Journal of visual languages and computing}, number = {5}, publisher = {Elsevier}, address = {London}, issn = {1045-926X}, doi = {10.1016/j.jvlc.2011.04.003}, pages = {385 -- 399}, year = {2011}, abstract = {Business processes are commonly modeled using a graphical modeling language. The most widespread notation for this purpose is business process diagrams in the Business Process Modeling Notation (BPMN). In this article, we use the visual query language BPMN-Q for expressing patterns that are related to possible problems in such business process diagrams. We discuss two classes of problems that can be found frequently in real-world models: sequence flow errors and model fragments that can make the model difficult to understand. By using a query processor, a business process modeler is able to identify possible errors in business process diagrams. Moreover, the erroneous parts of the business process diagram can be highlighted when an instance of an error pattern is found. This way, the modeler gets an easy-to-understand feedback in the visual modeling language he or she is familiar with. This is an advantage over current validation methods, which usually lack this kind of intuitive feedback.}, language = {en} } @article{ProtzmannSchuenemannRadusch2011, author = {Protzmann, Robert and Sch{\"u}nemann, Bjoern and Radusch, Ilja}, title = {The Influences of communication models on the simulated effectiveness of V2X Applications}, series = {IEEE communications magazine}, volume = {49}, journal = {IEEE communications magazine}, number = {11}, publisher = {Inst. of Electr. and Electronics Engineers}, address = {Piscataway}, issn = {0163-6804}, pages = {149 -- 155}, year = {2011}, abstract = {In this article, we aim to evaluate the influences of different propagation models on the results of V2X simulations. First, we analyze how the models free space propagation, Rayleigh fading, and Ricean fading in synthetic scenarios with and without background communication influence the simulation of communication in general. After that, we investigate the impact of the models on the simulated behavior of a V2X traffic efficiency application in a real inner city scenario. Our results show that the selection of the propagation model affects the number of delivered messages, but exerts no significant influence on the simulated effectiveness of a V2X traffic efficiency application in urban areas. Under those circumstances, a simplified propagation model is sufficient.}, language = {en} } @article{WistSchaeferVogleretal.2011, author = {Wist, Dominic and Schaefer, Mark and Vogler, Walter and Wollowski, Ralf}, title = {Signal transition graph decomposition internal communication for speed independent circuit implementation}, series = {IET Computers and digital techniques}, volume = {5}, journal = {IET Computers and digital techniques}, number = {6}, publisher = {Institution of Engineering and Technology}, address = {Hertford}, issn = {1751-8601}, doi = {10.1049/iet-cdt.2010.0162}, pages = {440 -- 451}, year = {2011}, abstract = {Logic synthesis of speed independent circuits based on signal transition graph (STG) decomposition is a promising approach to tackle complexity problems like state-space explosion. Unfortunately, decomposition can result in components that in isolation have irreducible complete state coding conflicts. In earlier work, the authors showed how to resolve such conflicts by introducing internal communication between components, but only for very restricted specification structures. Here, they improve their former work by presenting algorithms for identifying delay transitions and inserting gyroscopes for specifications having a much more general structure. Thus, the authors are now able to synthesise controllers from real-life specifications. For all algorithms, they present correctness proofs and show their successful application to benchmarks, including very complex STGs arising in the context of control resynthesis.}, language = {en} } @article{YeungNollGibbinsetal.2011, author = {Yeung, Ching-man Au and Noll, Michael G. and Gibbins, Nicholas and Meinel, Christoph and Shadbolt, Nigel}, title = {Spear spamming-resistant expertise analysis and ranking incollaborative tagging systems}, series = {Computational intelligence}, volume = {27}, journal = {Computational intelligence}, number = {3}, publisher = {Wiley-Blackwell}, address = {Hoboken}, issn = {0824-7935}, doi = {10.1111/j.1467-8640.2011.00384.x}, pages = {458 -- 488}, year = {2011}, abstract = {In this article, we discuss the notions of experts and expertise in resource discovery in the context of collaborative tagging systems. We propose that the level of expertise of a user with respect to a particular topic is mainly determined by two factors. First, an expert should possess a high-quality collection of resources, while the quality of a Web resource in turn depends on the expertise of the users who have assigned tags to it, forming a mutual reinforcement relationship. Second, an expert should be one who tends to identify interesting or useful resources before other users discover them, thus bringing these resources to the attention of the community of users. We propose a graph-based algorithm, SPEAR (spamming-resistant expertise analysis and ranking), which implements the above ideas for ranking users in a folksonomy. Our experiments show that our assumptions on expertise in resource discovery, and SPEAR as an implementation of these ideas, allow us to promote experts and demote spammers at the same time, with performance significantly better than the original hypertext-induced topic search algorithm and simple statistical measures currently used in most collaborative tagging systems.}, language = {en} } @article{SemmoHildebrandtTrappetal.2012, author = {Semmo, Amir and Hildebrandt, Dieter and Trapp, Matthias and D{\"o}llner, J{\"u}rgen Roland Friedrich}, title = {Concepts for cartography-oriented visualization of virtual 3D city models}, series = {Photogrammetrie, Fernerkundung, Geoinformation}, journal = {Photogrammetrie, Fernerkundung, Geoinformation}, number = {4}, publisher = {Schweizerbart}, address = {Stuttgart}, issn = {1432-8364}, doi = {10.1127/1432-8364/2012/0131}, pages = {455 -- 465}, year = {2012}, abstract = {Virtual 3D city models serve as an effective medium with manifold applications in geoinformation systems and services. To date, most 3D city models are visualized using photorealistic graphics. But an effective communication of geoinformation significantly depends on how important information is designed and cognitively processed in the given application context. One possibility to visually emphasize important information is based on non-photorealistic rendering, which comprehends artistic depiction styles and is characterized by its expressiveness and communication aspects. However, a direct application of non-photorealistic rendering techniques primarily results in monotonic visualization that lacks cartographic design aspects. In this work, we present concepts for cartography-oriented visualization of virtual 3D city models. These are based on coupling non-photorealistic rendering techniques and semantics-based information for a user, context, and media-dependent representation of thematic information. This work highlights challenges for cartography-oriented visualization of 3D geovirtual environments, presents stylization techniques and discusses their applications and ideas for a standardized visualization. In particular, the presented concepts enable a real-time and dynamic visualization of thematic geoinformation.}, language = {en} } @article{SemmoTrappKyprianidisetal.2012, author = {Semmo, Amir and Trapp, Matthias and Kyprianidis, Jan Eric and D{\"o}llner, J{\"u}rgen Roland Friedrich}, title = {Interactive visualization of generalized virtual 3D city models using level-of-abstraction transitions}, series = {Computer graphics forum : journal of the European Association for Computer Graphics}, volume = {31}, journal = {Computer graphics forum : journal of the European Association for Computer Graphics}, number = {3}, publisher = {Wiley-Blackwell}, address = {Hoboken}, issn = {0167-7055}, doi = {10.1111/j.1467-8659.2012.03081.x}, pages = {885 -- 894}, year = {2012}, abstract = {Virtual 3D city models play an important role in the communication of complex geospatial information in a growing number of applications, such as urban planning, navigation, tourist information, and disaster management. In general, homogeneous graphic styles are used for visualization. For instance, photorealism is suitable for detailed presentations, and non-photorealism or abstract stylization is used to facilitate guidance of a viewer's gaze to prioritized information. However, to adapt visualization to different contexts and contents and to support saliency-guided visualization based on user interaction or dynamically changing thematic information, a combination of different graphic styles is necessary. Design and implementation of such combined graphic styles pose a number of challenges, specifically from the perspective of real-time 3D visualization. In this paper, the authors present a concept and an implementation of a system that enables different presentation styles, their seamless integration within a single view, and parametrized transitions between them, which are defined according to tasks, camera view, and image resolution. The paper outlines potential usage scenarios and application fields together with a performance evaluation of the implementation.}, language = {en} } @article{HirschfeldPerscheidHaupt2012, author = {Hirschfeld, Robert and Perscheid, Michael and Haupt, Michael}, title = {Explicit use-case representation in object-oriented programming languages}, series = {ACM SIGPLAN notices}, volume = {47}, journal = {ACM SIGPLAN notices}, number = {2}, publisher = {Association for Computing Machinery}, address = {New York}, issn = {0362-1340}, doi = {10.1145/2168696.2047856}, pages = {51 -- 60}, year = {2012}, abstract = {Use-cases are considered an integral part of most contemporary development processes since they describe a software system's expected behavior from the perspective of its prospective users. However, the presence of and traceability to use-cases is increasingly lost in later more code-centric development activities. Use-cases, being well-encapsulated at the level of requirements descriptions, eventually lead to crosscutting concerns in system design and source code. Tracing which parts of the system contribute to which use-cases is therefore hard and so limits understandability. In this paper, we propose an approach to making use-cases first-class entities in both the programming language and the runtime environment. Having use-cases present in the code and the running system will allow developers, maintainers, and operators to easily associate their units of work with what matters to the users. We suggest the combination of use-cases, acceptance tests, and dynamic analysis to automatically associate source code with use-cases. We present UseCasePy, an implementation of our approach to use-case-centered development in Python, and its application to the Django Web framework.}, language = {en} } @unpublished{WeskeYangMaglio2012, author = {Weske, Mathias and Yang, Jian and Maglio, Paul P.}, title = {Special issue service oriented computing (ICSOC) guest editors' introduction}, series = {International journal of cooperative information systems}, volume = {21}, journal = {International journal of cooperative information systems}, number = {1}, publisher = {World Scientific}, address = {Singapore}, issn = {0218-8430}, doi = {10.1142/S0218843012020017}, pages = {1 -- 2}, year = {2012}, language = {en} } @article{WeidlichMendling2012, author = {Weidlich, Matthias and Mendling, Jan}, title = {Perceived consistency between process models}, series = {Information systems}, volume = {37}, journal = {Information systems}, number = {2}, publisher = {Elsevier}, address = {Oxford}, issn = {0306-4379}, doi = {10.1016/j.is.2010.12.004}, pages = {80 -- 98}, year = {2012}, abstract = {Process-aware information systems typically involve various kinds of process stakeholders. That, in turn, leads to multiple process models that capture a common process from different perspectives and at different levels of abstraction. In order to guarantee a certain degree of uniformity, the consistency of such related process models is evaluated using formal criteria. However, it is unclear how modelling experts assess the consistency between process models, and which kind of notion they perceive to be appropriate. In this paper, we focus on control flow aspects and investigate the adequacy of consistency notions. In particular, we report findings from an online experiment, which allows us to compare in how far trace equivalence and two notions based on behavioural profiles approximate expert perceptions on consistency. Analysing 69 expert statements from process analysts, we conclude that trace equivalence is not suited to be applied as a consistency notion, whereas the notions based on behavioural profiles approximate the perceived consistency of our subjects significantly. Therefore, our contribution is an empirically founded answer to the correlation of behaviour consistency notions and the consistency perception by experts in the field of business process modelling.}, language = {en} } @article{YangDumasGarciaBanuelosetal.2012, author = {Yang, Yong and Dumas, Marlon and Garcia-Banuelos, Luciano and Polyvyanyy, Artem and Zhang, Liang}, title = {Generalized aggregate quality of service computation for composite services}, series = {The journal of systems and software}, volume = {85}, journal = {The journal of systems and software}, number = {8}, publisher = {Elsevier}, address = {New York}, issn = {0164-1212}, doi = {10.1016/j.jss.2012.03.005}, pages = {1818 -- 1830}, year = {2012}, abstract = {This article addresses the problem of estimating the Quality of Service (QoS) of a composite service given the QoS of the services participating in the composition. Previous solutions to this problem impose restrictions on the topology of the orchestration models, limiting their applicability to well-structured orchestration models for example. This article lifts these restrictions by proposing a method for aggregate QoS computation that deals with more general types of unstructured orchestration models. The applicability and scalability of the proposed method are validated using a collection of models from industrial practice.}, language = {en} } @article{WeidlichMendlingWeske2012, author = {Weidlich, Matthias and Mendling, Jan and Weske, Mathias}, title = {Propagating changes between aligned process models}, series = {The journal of systems and software}, volume = {85}, journal = {The journal of systems and software}, number = {8}, publisher = {Elsevier}, address = {New York}, issn = {0164-1212}, doi = {10.1016/j.jss.2012.02.044}, pages = {1885 -- 1898}, year = {2012}, abstract = {There is a wide variety of drivers for business process modelling initiatives, reaching from organisational redesign to the development of information systems. Consequently, a common business process is often captured in multiple models that overlap in content due to serving different purposes. Business process management aims at flexible adaptation to changing business needs. Hence, changes of business processes occur frequently and have to be incorporated in the respective process models. Once a process model is changed, related process models have to be updated accordingly, despite the fact that those process models may only be loosely coupled. In this article, we introduce an approach that supports change propagation between related process models. Given a change in one process model, we leverage the behavioural abstraction of behavioural profiles for corresponding activities in order to determine a change region in another model. Our approach is able to cope with changes in pairs of models that are not related by hierarchical refinement and show behavioural inconsistencies. We evaluate the applicability of our approach with two real-world process model collections. To this end, we either deduce change operations from different model revisions or rely on synthetic change operations.}, language = {en} } @article{EhrigGolasHabeletal.2012, author = {Ehrig, Hartmut and Golas, Ulrike and Habel, Annegret and Lambers, Leen and Orejas, Fernando}, title = {M-Adhesive Transformation Systems with Nested Application Conditions Part 2: Embedding, Critical Pairs and Local Confluence}, series = {Fundamenta informaticae}, volume = {118}, journal = {Fundamenta informaticae}, number = {1-2}, publisher = {IOS Press}, address = {Amsterdam}, issn = {0169-2968}, doi = {10.3233/FI-2012-705}, pages = {35 -- 63}, year = {2012}, abstract = {Graph transformation systems have been studied extensively and applied to several areas of computer science like formal language theory, the modeling of databases, concurrent or distributed systems, and visual, logical, and functional programming. In most kinds of applications it is necessary to have the possibility of restricting the applicability of rules. This is usually done by means of application conditions. In this paper, we continue the work of extending the fundamental theory of graph transformation to the case where rules may use arbitrary (nested) application conditions. More precisely, we generalize the Embedding theorem, and we study how local confluence can be checked in this context. In particular, we define a new notion of critical pair which allows us to formulate and prove a Local Confluence Theorem for the general case of rules with nested application conditions. All our results are presented, not for a specific class of graphs, but for any arbitrary M-adhesive category, which means that our results apply to most kinds of graphical structures. We demonstrate our theory on the modeling of an elevator control by a typed graph transformation system with positive and negative application conditions.}, language = {en} } @article{OrejasLambers2012, author = {Orejas, Fernando and Lambers, Leen}, title = {Lazy graph transformation}, series = {Fundamenta informaticae}, volume = {118}, journal = {Fundamenta informaticae}, number = {1-2}, publisher = {IOS Press}, address = {Amsterdam}, issn = {0169-2968}, doi = {10.3233/FI-2012-706}, pages = {65 -- 96}, year = {2012}, abstract = {Applying an attributed graph transformation rule to a given object graph always implies some kind of constraint solving. In many cases, the given constraints are almost trivial to solve. For instance, this is the case when a rule describes a transformation G double right arrow H, where the attributes of H are obtained by some simple computation from the attributes of G. However there are many other cases where the constraints to solve may be not so trivial and, moreover, may have several answers. This is the case, for instance, when the transformation process includes some kind of searching. In the current approaches to attributed graph transformation these constraints must be completely solved when defining the matching of the given transformation rule. This kind of early binding is well-known from other areas of Computer Science to be inadequate. For instance, the solution chosen for the constraints associated to a given transformation step may be not fully adequate, meaning that later, in the search for a better solution, we may need to backtrack this transformation step. In this paper, based on our previous work on the use of symbolic graphs to deal with different aspects related with attributed graphs, including attributed graph transformation, we present a new approach that, based on the new notion of narrowing graph transformation rule, allows us to delay constraint solving when doing attributed graph transformation, in a way that resembles lazy computation. For this reason, we have called lazy this new kind of transformation. Moreover, we show that the approach is sound and complete with respect to standard attributed graph transformation. A running example, where a graph transformation system describes some basic operations of a travel agency, shows the practical interest of the approach.}, language = {en} } @article{WeidlichDijkmanWeske2012, author = {Weidlich, Matthias and Dijkman, Remco and Weske, Mathias}, title = {Behaviour equivalence and compatibility of business process models with complex correspondences}, series = {The computer journal : a publication of the British Computer Society}, volume = {55}, journal = {The computer journal : a publication of the British Computer Society}, number = {11}, publisher = {Oxford Univ. Press}, address = {Oxford}, issn = {0010-4620}, doi = {10.1093/comjnl/bxs014}, pages = {1398 -- 1418}, year = {2012}, abstract = {Once multiple models of a business process are created for different purposes or to capture different variants, verification of behaviour equivalence or compatibility is needed. Equivalence verification ensures that two business process models specify the same behaviour. Since different process models are likely to differ with respect to their assumed level of abstraction and the actions that they take into account, equivalence notions have to cope with correspondences between sets of actions and actions that exist in one process but not in the other. In this paper, we present notions of equivalence and compatibility that can handle these problems. In essence, we present a notion of equivalence that works on correspondences between sets of actions rather than single actions. We then integrate our equivalence notion with work on behaviour inheritance that copes with actions that exist in one process but not in the other, leading to notions of behaviour compatibility. Compatibility notions verify that two models have the same behaviour with respect to the actions that they have in common. As such, our contribution is a collection of behaviour equivalence and compatibility notions that are applicable in more general settings than existing ones.}, language = {en} } @article{PolyvyanyyGarciaBanuelosDumas2012, author = {Polyvyanyy, Artem and Garcia-Banuelos, Luciano and Dumas, Marlon}, title = {Structuring acyclic process models}, series = {Information systems}, volume = {37}, journal = {Information systems}, number = {6}, publisher = {Elsevier}, address = {Oxford}, issn = {0306-4379}, doi = {10.1016/j.is.2011.10.005}, pages = {518 -- 538}, year = {2012}, abstract = {This article studies the problem of transforming a process model with an arbitrary topology into an equivalent well-structured process model. While this problem has received significant attention, there is still no full characterization of the class of unstructured process models that can be transformed into well-structured ones, nor an automated method for structuring any process model that belongs to this class. This article fills this gap in the context of acyclic process models. The article defines a necessary and sufficient condition for an unstructured acyclic process model to have an equivalent well-structured process model under fully concurrent bisimulation, as well as a complete structuring method. The method has been implemented as a tool that takes process models captured in the BPMN and EPC notations as input. The article also reports on an empirical evaluation of the structuring method using a repository of process models from commercial practice.}, language = {en} } @article{KuehneHuitemaCarle2012, author = {K{\"u}hne, Ralph and Huitema, George and Carle, George}, title = {Charging and billing in modern communications networks a comprehensive survey of the state of the art and future requirements}, series = {IEEE communications surveys \& tutorials}, volume = {14}, journal = {IEEE communications surveys \& tutorials}, number = {1}, publisher = {Inst. of Electr. and Electronics Engineers}, address = {Piscataway}, issn = {1553-877X}, doi = {10.1109/SURV.2011.122310.000084}, pages = {170 -- 192}, year = {2012}, abstract = {In mobile telecommunication networks the trend for an increasing heterogeneity of access networks, the convergence with fixed networks as well as with the Internet are apparent. The resulting future converged network with an expected wide variety of services and a possibly stiff competition between the different market participants as well as legal issues will bring about requirements for charging systems that demand for more flexibility, scalability and efficiency than is available in today's systems. This article surveys recent developments in charging and billing architectures comprising both standardisation work as well as research projects. The second main contribution of this article is a comparison of key features of these developments thus giving a list of essential charging and billing ingredients for tomorrow's communication and service environments.}, language = {en} } @article{RoschkeChengMeinel2012, author = {Roschke, Sebastian and Cheng, Feng and Meinel, Christoph}, title = {An alert correlation platform for memory-supported techniques}, series = {Concurrency and computation : practice \& experience}, volume = {24}, journal = {Concurrency and computation : practice \& experience}, number = {10}, publisher = {Wiley-Blackwell}, address = {Hoboken}, issn = {1532-0626}, doi = {10.1002/cpe.1750}, pages = {1123 -- 1136}, year = {2012}, abstract = {Intrusion Detection Systems (IDS) have been widely deployed in practice for detecting malicious behavior on network communication and hosts. False-positive alerts are a popular problem for most IDS approaches. The solution to address this problem is to enhance the detection process by correlation and clustering of alerts. To meet the practical requirements, this process needs to be finished fast, which is a challenging task as the amount of alerts in large-scale IDS deployments is significantly high. We identifytextitdata storage and processing algorithms to be the most important factors influencing the performance of clustering and correlation. We propose and implement a highly efficient alert correlation platform. For storage, a column-based database, an In-Memory alert storage, and memory-based index tables lead to significant improvements of the performance. For processing, algorithms are designed and implemented which are optimized for In-Memory databases, e.g. an attack graph-based correlation algorithm. The platform can be distributed over multiple processing units to share memory and processing power. A standardized interface is designed to provide a unified view of result reports for end users. The efficiency of the platform is tested by practical experiments with several alert storage approaches, multiple algorithms, as well as a local and a distributed deployment.}, language = {en} } @article{QuasthoffMeinel2012, author = {Quasthoff, Matthias and Meinel, Christoph}, title = {Supporting object-oriented programming of semantic-web software}, series = {IEEE transactions on systems, man, and cybernetics : Part C, Applications and reviews}, volume = {42}, journal = {IEEE transactions on systems, man, and cybernetics : Part C, Applications and reviews}, number = {1}, publisher = {Inst. of Electr. and Electronics Engineers}, address = {Piscataway}, issn = {1094-6977}, doi = {10.1109/TSMCC.2011.2151282}, pages = {15 -- 24}, year = {2012}, abstract = {This paper presents the state of the art in the development of Semantic-Web-enabled software using object-oriented programming languages. Object triple mapping (OTM) is a frequently used method to simplify the development of such software. A case study that is based on interviews with developers of OTM frameworks is presented at the core of this paper. Following the results of the case study, the formalization of OTM is kept separate from optional but desirable extensions of OTM with regard to metadata, schema matching, and integration into the Semantic-Web infrastructure. The material that is presented is expected to not only explain the development of Semantic-Web software by the usage of OTM, but also explain what properties of Semantic-Web software made developers come up with OTM. Understanding the latter will be essential to get nonexpert software developers to use Semantic-Web technologies in their software.}, language = {en} } @article{RafieevonLoewisMeinel2012, author = {Rafiee, Hosnieh and von Loewis, Martin and Meinel, Christoph}, title = {IPv6 Deployment and Spam Challenges}, series = {IEEE Internet computing}, volume = {16}, journal = {IEEE Internet computing}, number = {6}, publisher = {Inst. of Electr. and Electronics Engineers}, address = {Los Alamitos}, issn = {1089-7801}, pages = {22 -- 29}, year = {2012}, abstract = {Spam has posed a serious problem for users of email since its infancy. Today, automated strategies are required to deal with the massive amount of spam traffic. IPv4 networks offer a variety of solutions to reduce spam, but IPv6 networks' large address space and use of temporary addresses - both of which are particularly vulnerable to spam attacks - makes dealing with spam and the use of automated approaches much more difficult. IPv6 thus poses a unique security issue for ISPs because it's more difficult for them to differentiate between good IP addresses and those that are known to originate spam messages.}, language = {en} } @article{AlSa'dehMeinel2012, author = {AlSa'deh, Ahmad and Meinel, Christoph}, title = {Secure neighbor discovery Review, challenges, perspectives, and recommendations}, series = {IEEE security \& privacy : building confidence in a networked world}, volume = {10}, journal = {IEEE security \& privacy : building confidence in a networked world}, number = {4}, publisher = {Inst. of Electr. and Electronics Engineers}, address = {Los Alamitos}, issn = {1540-7993}, pages = {26 -- 34}, year = {2012}, abstract = {Secure Neighbor Discovery is designed as a countermeasure to Neighbor Discovery Protocol threats. The authors discuss Secure Neighbor Discovery implementation and deployment challenges and review proposals to optimize it.}, language = {en} } @article{MomtaziNaumann2013, author = {Momtazi, Saeedeh and Naumann, Felix}, title = {Topic modeling for expert finding using latent Dirichlet allocation}, series = {Wiley interdisciplinary reviews : Data mining and knowledge discovery}, volume = {3}, journal = {Wiley interdisciplinary reviews : Data mining and knowledge discovery}, number = {5}, publisher = {Wiley}, address = {San Fransisco}, issn = {1942-4787}, doi = {10.1002/widm.1102}, pages = {346 -- 353}, year = {2013}, abstract = {The task of expert finding is to rank the experts in the search space given a field of expertise as an input query. In this paper, we propose a topic modeling approach for this task. The proposed model uses latent Dirichlet allocation (LDA) to induce probabilistic topics. In the first step of our algorithm, the main topics of a document collection are extracted using LDA. The extracted topics present the connection between expert candidates and user queries. In the second step, the topics are used as a bridge to find the probability of selecting each candidate for a given query. The candidates are then ranked based on these probabilities. The experimental results on the Text REtrieval Conference (TREC) Enterprise track for 2005 and 2006 show that the proposed topic-based approach outperforms the state-of-the-art profile- and document-based models, which use information retrieval methods to rank experts. Moreover, we present the superiority of the proposed topic-based approach to the improved document-based expert finding systems, which consider additional information such as local context, candidate prior, and query expansion.}, language = {en} } @unpublished{FishLambers2013, author = {Fish, Andrew and Lambers, Leen}, title = {Special issue on graph transformation and visual modeling techniques - guest editors' introduction}, series = {Journal of visual languages and computing}, volume = {24}, journal = {Journal of visual languages and computing}, number = {6}, publisher = {Elsevier}, address = {London}, issn = {1045-926X}, doi = {10.1016/j.jvlc.2013.08.004}, pages = {419 -- 420}, year = {2013}, language = {en} } @article{RoschkeChengMeinel2013, author = {Roschke, Sebastian and Cheng, Feng and Meinel, Christoph}, title = {High-quality attack graph-based IDS correlation}, series = {Logic journal of the IGPL}, volume = {21}, journal = {Logic journal of the IGPL}, number = {4}, publisher = {Oxford Univ. Press}, address = {Oxford}, issn = {1367-0751}, doi = {10.1093/jigpal/jzs034}, pages = {571 -- 591}, year = {2013}, abstract = {Intrusion Detection Systems are widely deployed in computer networks. As modern attacks are getting more sophisticated and the number of sensors and network nodes grow, the problem of false positives and alert analysis becomes more difficult to solve. Alert correlation was proposed to analyse alerts and to decrease false positives. Knowledge about the target system or environment is usually necessary for efficient alert correlation. For representing the environment information as well as potential exploits, the existing vulnerabilities and their Attack Graph (AG) is used. It is useful for networks to generate an AG and to organize certain vulnerabilities in a reasonable way. In this article, a correlation algorithm based on AGs is designed that is capable of detecting multiple attack scenarios for forensic analysis. It can be parameterized to adjust the robustness and accuracy. A formal model of the algorithm is presented and an implementation is tested to analyse the different parameters on a real set of alerts from a local network. To improve the speed of the algorithm, a multi-core version is proposed and a HMM-supported version can be used to further improve the quality. The parallel implementation is tested on a multi-core correlation platform, using CPUs and GPUs.}, language = {en} } @article{RichterDoellner2014, author = {Richter, Rico and D{\"o}llner, J{\"u}rgen Roland Friedrich}, title = {Concepts and techniques for integration, analysis and visualization of massive 3D point clouds}, series = {Computers, environment and urban systems}, volume = {45}, journal = {Computers, environment and urban systems}, publisher = {Elsevier}, address = {Oxford}, issn = {0198-9715}, doi = {10.1016/j.compenvurbsys.2013.07.004}, pages = {114 -- 124}, year = {2014}, abstract = {Remote sensing methods, such as LiDAR and image-based photogrammetry, are established approaches for capturing the physical world. Professional and low-cost scanning devices are capable of generating dense 3D point clouds. Typically, these 3D point clouds are preprocessed by GIS and are then used as input data in a variety of applications such as urban planning, environmental monitoring, disaster management, and simulation. The availability of area-wide 3D point clouds will drastically increase in the future due to the availability of novel capturing methods (e.g., driver assistance systems) and low-cost scanning devices. Applications, systems, and workflows will therefore face large collections of redundant, up-to-date 3D point clouds and have to cope with massive amounts of data. Hence, approaches are required that will efficiently integrate, update, manage, analyze, and visualize 3D point clouds. In this paper, we define requirements for a system infrastructure that enables the integration of 3D point clouds from heterogeneous capturing devices and different timestamps. Change detection and update strategies for 3D point clouds are presented that reduce storage requirements and offer new insights for analysis purposes. We also present an approach that attributes 3D point clouds with semantic information (e.g., object class category information), which enables more effective data processing, analysis, and visualization. Out-of-core real-time rendering techniques then allow for an interactive exploration of the entire 3D point cloud and the corresponding analysis results. Web-based visualization services are utilized to make 3D point clouds available to a large community. The proposed concepts and techniques are designed to establish 3D point clouds as base datasets, as well as rendering primitives for analysis and visualization tasks, which allow operations to be performed directly on the point data. Finally, we evaluate the presented system, report on its applications, and discuss further research challenges.}, language = {en} } @article{MarrPapeDeMeuter2014, author = {Marr, Stefan and Pape, Tobias and De Meuter, Wolfgang}, title = {Are we there yet? Simple language implementation techniques for the 21st century}, series = {IEEE software}, volume = {31}, journal = {IEEE software}, number = {5}, publisher = {Inst. of Electr. and Electronics Engineers}, address = {Los Alamitos}, issn = {0740-7459}, pages = {60 -- 67}, year = {2014}, language = {en} } @article{WeidlichZiekowGaletal.2014, author = {Weidlich, Matthias and Ziekow, Holger and Gal, Avigdor and Mendling, Jan and Weske, Mathias}, title = {Optimizing event pattern matching using business process models}, series = {IEEE transactions on knowledge and data engineering}, volume = {26}, journal = {IEEE transactions on knowledge and data engineering}, number = {11}, publisher = {Inst. of Electr. and Electronics Engineers}, address = {Los Alamitos}, issn = {1041-4347}, doi = {10.1109/TKDE.2014.2302306}, pages = {2759 -- 2773}, year = {2014}, abstract = {A growing number of enterprises use complex event processing for monitoring and controlling their operations, while business process models are used to document working procedures. In this work, we propose a comprehensive method for complex event processing optimization using business process models. Our proposed method is based on the extraction of behaviorial constraints that are used, in turn, to rewrite patterns for event detection, and select and transform execution plans. We offer a set of rewriting rules that is shown to be complete with respect to the all, seq, and any patterns. The effectiveness of our method is demonstrated in an experimental evaluation with a large number of processes from an insurance company. We illustrate that the proposed optimization leads to significant savings in query processing. By integrating the optimization in state-of-the-art systems for event pattern matching, we demonstrate that these savings materialize in different technical infrastructures and can be combined with existing optimization techniques.}, language = {en} } @article{HildebrandtTimm2014, author = {Hildebrandt, Dieter and Timm, Robert}, title = {An assisting, constrained 3D navigation technique for multiscale virtual 3D city models}, series = {Geoinformatica : an international journal on advances of computer science for geographic information systems}, volume = {18}, journal = {Geoinformatica : an international journal on advances of computer science for geographic information systems}, number = {3}, publisher = {Springer}, address = {Dordrecht}, issn = {1384-6175}, doi = {10.1007/s10707-013-0189-8}, pages = {537 -- 567}, year = {2014}, abstract = {Virtual 3D city models serve as integration platforms for complex geospatial and georeferenced information and as medium for effective communication of spatial information. In order to explore these information spaces, navigation techniques for controlling the virtual camera are required to facilitate wayfinding and movement. However, navigation is not a trivial task and many available navigation techniques do not support users effectively and efficiently with their respective skills and tasks. In this article, we present an assisting, constrained navigation technique for multiscale virtual 3D city models that is based on three basic principles: users point to navigate, users are lead by suggestions, and the exploitation of semantic, multiscale, hierarchical structurings of city models. The technique particularly supports users with low navigation and virtual camera control skills but is also valuable for experienced users. It supports exploration, search, inspection, and presentation tasks, is easy to learn and use, supports orientation, is efficient, and yields effective view properties. In particular, the technique is suitable for interactive kiosks and mobile devices with a touch display and low computing resources and for use in mobile situations where users only have restricted resources for operating the application. We demonstrate the validity of the proposed navigation technique by presenting an implementation and evaluation results. The implementation is based on service-oriented architectures, standards, and image-based representations and allows exploring massive virtual 3D city models particularly on mobile devices with limited computing resources. Results of a user study comparing the proposed navigation technique with standard techniques suggest that the proposed technique provides the targeted properties, and that it is more advantageous to novice than to expert users.}, language = {en} } @article{YangQuehlSack2014, author = {Yang, Haojin and Quehl, Bernhard and Sack, Harald}, title = {A framework for improved video text detection and recognition}, series = {Multimedia tools and applications : an international journal}, volume = {69}, journal = {Multimedia tools and applications : an international journal}, number = {1}, publisher = {Springer}, address = {Dordrecht}, issn = {1380-7501}, doi = {10.1007/s11042-012-1250-6}, pages = {217 -- 245}, year = {2014}, abstract = {Text displayed in a video is an essential part for the high-level semantic information of the video content. Therefore, video text can be used as a valuable source for automated video indexing in digital video libraries. In this paper, we propose a workflow for video text detection and recognition. In the text detection stage, we have developed a fast localization-verification scheme, in which an edge-based multi-scale text detector first identifies potential text candidates with high recall rate. Then, detected candidate text lines are refined by using an image entropy-based filter. Finally, Stroke Width Transform (SWT)- and Support Vector Machine (SVM)-based verification procedures are applied to eliminate the false alarms. For text recognition, we have developed a novel skeleton-based binarization method in order to separate text from complex backgrounds to make it processible for standard OCR (Optical Character Recognition) software. Operability and accuracy of proposed text detection and binarization methods have been evaluated by using publicly available test data sets.}, language = {en} } @article{BuchwaldWagelaarDanetal.2014, author = {Buchwald, Sebastian and Wagelaar, Dennis and Dan, Li and Hegedues, Abel and Herrmannsdoerfer, Markus and Horn, Tassilo and Kalnina, Elina and Krause, Christian and Lano, Kevin and Lepper, Markus and Rensink, Arend and Rose, Louis and Waetzoldt, Sebastian and Mazanek, Steffen}, title = {A survey and comparison of transformation tools based on the transformation tool contest}, series = {Science of computer programming}, volume = {85}, journal = {Science of computer programming}, publisher = {Elsevier}, address = {Amsterdam}, issn = {0167-6423}, doi = {10.1016/j.scico.2013.10.009}, pages = {41 -- 99}, year = {2014}, abstract = {Model transformation is one of the key tasks in model-driven engineering and relies on the efficient matching and modification of graph-based data structures; its sibling graph rewriting has been used to successfully model problems in a variety of domains. Over the last years, a wide range of graph and model transformation tools have been developed all of them with their own particular strengths and typical application domains. In this paper, we give a survey and a comparison of the model and graph transformation tools that participated at the Transformation Tool Contest 2011. The reader gains an overview of the field and its tools, based on the illustrative solutions submitted to a Hello World task, and a comparison alongside a detailed taxonomy. The article is of interest to researchers in the field of model and graph transformation, as well as to software engineers with a transformation task at hand who have to choose a tool fitting to their needs. All solutions referenced in this article provide a SHARE demo. It supported the peer-review process for the contest, and now allows the reader to test the tools online.}, language = {en} } @article{Hildebrandt2014, author = {Hildebrandt, Dieter}, title = {A software reference architecture for service-oriented 3D geovisualization systems}, series = {ISPRS International Journal of Geo-Information}, volume = {3}, journal = {ISPRS International Journal of Geo-Information}, number = {4}, publisher = {MDPI}, address = {Basel}, issn = {2220-9964}, doi = {10.3390/ijgi3041445}, pages = {1445 -- 1490}, year = {2014}, language = {en} } @article{EhrigGolasHabeletal.2014, author = {Ehrig, Hartmut and Golas, Ulrike and Habel, Annegret and Lambers, Leen and Orejas, Fernando}, title = {M-adhesive transformation systems with nested application conditions. Part 1: parallelism, concurrency and amalgamation}, series = {Mathematical structures in computer science : a journal in the applications of categorical, algebraic and geometric methods in computer science}, volume = {24}, journal = {Mathematical structures in computer science : a journal in the applications of categorical, algebraic and geometric methods in computer science}, number = {4}, publisher = {Cambridge Univ. Press}, address = {New York}, issn = {0960-1295}, doi = {10.1017/S0960129512000357}, pages = {48}, year = {2014}, abstract = {Nested application conditions generalise the well-known negative application conditions and are important for several application domains. In this paper, we present Local Church-Rosser, Parallelism, Concurrency and Amalgamation Theorems for rules with nested application conditions in the framework of M-adhesive categories, where M-adhesive categories are slightly more general than weak adhesive high-level replacement categories. Most of the proofs are based on the corresponding statements for rules without application conditions and two shift lemmas stating that nested application conditions can be shifted over morphisms and rules.}, language = {en} } @article{WestphalAxelssonNeuhausetal.2014, author = {Westphal, Florian and Axelsson, Stefan and Neuhaus, Christian and Polze, Andreas}, title = {VMI-PL: A monitoring language for virtual platforms using virtual machine introspection}, series = {Digital Investigation : the international journal of digital forensics \& incident response}, volume = {11}, journal = {Digital Investigation : the international journal of digital forensics \& incident response}, publisher = {Elsevier}, address = {Oxford}, issn = {1742-2876}, doi = {10.1016/j.diin.2014.05.016}, pages = {S85 -- S94}, year = {2014}, abstract = {With the growth of virtualization and cloud computing, more and more forensic investigations rely on being able to perform live forensics on a virtual machine using virtual machine introspection (VMI). Inspecting a virtual machine through its hypervisor enables investigation without risking contamination of the evidence, crashing the computer, etc. To further access to these techniques for the investigator/researcher we have developed a new VMI monitoring language. This language is based on a review of the most commonly used VMI-techniques to date, and it enables the user to monitor the virtual machine's memory, events and data streams. A prototype implementation of our monitoring system was implemented in KVM, though implementation on any hypervisor that uses the common x86 virtualization hardware assistance support should be straightforward. Our prototype outperforms the proprietary VMWare VProbes in many cases, with a maximum performance loss of 18\% for a realistic test case, which we consider acceptable. Our implementation is freely available under a liberal software distribution license. (C) 2014 Digital Forensics Research Workshop. Published by Elsevier Ltd. All rights reserved.}, language = {en} } @article{PolyvyanyyGarciaBanuelosFahlandetal.2014, author = {Polyvyanyy, Artem and Garcia-Banuelos, Luciano and Fahland, Dirk and Weske, Mathias}, title = {Maximal structuring of acyclic process models}, series = {The computer journal : a publication of the British Computer Society}, volume = {57}, journal = {The computer journal : a publication of the British Computer Society}, number = {1}, publisher = {Oxford Univ. Press}, address = {Oxford}, issn = {0010-4620}, doi = {10.1093/comjnl/bxs126}, pages = {12 -- 35}, year = {2014}, abstract = {This article addresses the transformation of a process model with an arbitrary topology into an equivalent structured process model. In particular, this article studies the subclass of process models that have no equivalent well-structured representation but which, nevertheless, can be partially structured into their maximally-structured representation. The transformations are performed under a behavioral equivalence notion that preserves the observed concurrency of tasks in equivalent process models. The article gives a full characterization of the subclass of acyclic process models that have no equivalent well-structured representation, but do have an equivalent maximally-structured one, as well as proposes a complete structuring method. Together with our previous results, this article completes the solution of the process model structuring problem for the class of acyclic process models.}, language = {en} } @article{VogelGiese2014, author = {Vogel, Thomas and Giese, Holger}, title = {Model-Driven engineering of self-adaptive software with EUREMA}, series = {ACM transactions on autonomous and adaptive systems}, volume = {8}, journal = {ACM transactions on autonomous and adaptive systems}, number = {4}, publisher = {Association for Computing Machinery}, address = {New York}, issn = {1556-4665}, doi = {10.1145/2555612}, pages = {33}, year = {2014}, abstract = {The development of self-adaptive software requires the engineering of an adaptation engine that controls the underlying adaptable software by feedback loops. The engine often describes the adaptation by runtime models representing the adaptable software and by activities such as analysis and planning that use these models. To systematically address the interplay between runtime models and adaptation activities, runtime megamodels have been proposed. A runtime megamodel is a specific model capturing runtime models and adaptation activities. In this article, we go one step further and present an executable modeling language for ExecUtable RuntimE MegAmodels (EUREMA) that eases the development of adaptation engines by following a model-driven engineering approach. We provide a domain-specific modeling language and a runtime interpreter for adaptation engines, in particular feedback loops. Megamodels are kept alive at runtime and by interpreting them, they are directly executed to run feedback loops. Additionally, they can be dynamically adjusted to adapt feedback loops. Thus, EUREMA supports development by making feedback loops explicit at a higher level of abstraction and it enables solutions where multiple feedback loops interact or operate on top of each other and self-adaptation co-exists with offline adaptation for evolution.}, language = {en} } @article{PasewaldtSemmoTrappetal.2014, author = {Pasewaldt, Sebastian and Semmo, Amir and Trapp, Matthias and D{\"o}llner, J{\"u}rgen}, title = {Multi-perspective 3D panoramas}, series = {International journal of geographical information science}, volume = {28}, journal = {International journal of geographical information science}, number = {10}, publisher = {Routledge, Taylor \& Francis Group}, address = {Abingdon}, issn = {1365-8816}, doi = {10.1080/13658816.2014.922686}, pages = {2030 -- 2051}, year = {2014}, abstract = {This article presents multi-perspective 3D panoramas that focus on visualizing 3D geovirtual environments (3D GeoVEs) for navigation and exploration tasks. Their key element, a multi-perspective view (MPV), seamlessly combines what is seen from multiple viewpoints into a single image. This approach facilitates the presentation of information for virtual 3D city and landscape models, particularly by reducing occlusions, increasing screen-space utilization, and providing additional context within a single image. We complement MPVs with cartographic visualization techniques to stylize features according to their semantics and highlight important or prioritized information. When combined, both techniques constitute the core implementation of interactive, multi-perspective 3D panoramas. They offer a large number of effective means for visual communication of 3D spatial information, a high degree of customization with respect to cartographic design, and manifold applications in different domains. We discuss design decisions of 3D panoramas for the exploration of and navigation in 3D GeoVEs. We also discuss a preliminary user study that indicates that 3D panoramas are a promising approach for navigation systems using 3D GeoVEs.}, language = {en} } @article{TakounaSachsMeinel2014, author = {Takouna, Ibrahim and Sachs, Kai and Meinel, Christoph}, title = {Multiperiod robust optimization for proactive resource provisioning in virtualized data centers}, series = {The journal of supercomputing : an internat. journal of supercomputer design, analysis and use}, volume = {70}, journal = {The journal of supercomputing : an internat. journal of supercomputer design, analysis and use}, number = {3}, publisher = {Springer}, address = {Dordrecht}, issn = {0920-8542}, doi = {10.1007/s11227-014-1246-2}, pages = {1514 -- 1536}, year = {2014}, language = {en} } @article{SemmoDoellner2015, author = {Semmo, Amir and D{\"o}llner, J{\"u}rgen Roland Friedrich}, title = {Interactive image filtering for level-of-abstraction texturing of virtual 3D scenes}, series = {Computers \& graphics : CAG ; an international journal of applications in computer graphics}, volume = {52}, journal = {Computers \& graphics : CAG ; an international journal of applications in computer graphics}, publisher = {Elsevier}, address = {Oxford}, issn = {0097-8493}, doi = {10.1016/j.cag.2015.02.001}, pages = {181 -- 198}, year = {2015}, abstract = {Texture mapping is a key technology in computer graphics. For the visual design of 3D scenes, in particular, effective texturing depends significantly on how important contents are expressed, e.g., by preserving global salient structures, and how their depiction is cognitively processed by the user in an application context. Edge-preserving image filtering is one key approach to address these concerns. Much research has focused on applying image filters in a post-process stage to generate artistically stylized depictions. However, these approaches generally do not preserve depth cues, which are important for the perception of 3D visualization (e.g., texture gradient). To this end, filtering is required that processes texture data coherently with respect to linear perspective and spatial relationships. In this work, we present an approach for texturing 3D scenes with perspective coherence by arbitrary image filters. We propose decoupled deferred texturing with (1) caching strategies to interactively perform image filtering prior to texture mapping and (2) for each mipmap level separately to enable a progressive level of abstraction, using (3) direct interaction interfaces to parameterize the visualization according to spatial, semantic, and thematic data. We demonstrate the potentials of our method by several applications using touch or natural language inputs to serve the different interests of users in specific information, including illustrative visualization, focus+context visualization, geometric detail removal, and semantic depth of field. The approach supports frame-to-frame coherence, order-independent transparency, multitexturing, and content-based filtering. In addition, it seamlessly integrates into real-time rendering pipelines and is extensible for custom interaction techniques. (C) 2015 Elsevier Ltd. All rights reserved.}, language = {en} } @article{SemmoTrappJobstetal.2015, author = {Semmo, Amir and Trapp, Matthias and Jobst, Markus and D{\"o}llner, J{\"u}rgen Roland Friedrich}, title = {Cartography-Oriented Design of 3D Geospatial Information Visualization - Overview and Techniques}, series = {The cartographic journal}, volume = {52}, journal = {The cartographic journal}, number = {2}, publisher = {Routledge, Taylor \& Francis Group}, address = {Leeds}, issn = {0008-7041}, doi = {10.1080/00087041.2015.1119462}, pages = {95 -- 106}, year = {2015}, abstract = {In economy, society and personal life map-based interactive geospatial visualization becomes a natural element of a growing number of applications and systems. The visualization of 3D geospatial information, however, raises the question how to represent the information in an effective way. Considerable research has been done in technology-driven directions in the fields of cartography and computer graphics (e.g., design principles, visualization techniques). Here, non-photorealistic rendering (NPR) represents a promising visualization category - situated between both fields - that offers a large number of degrees for the cartography-oriented visual design of complex 2D and 3D geospatial information for a given application context. Still today, however, specifications and techniques for mapping cartographic design principles to the state-of-the-art rendering pipeline of 3D computer graphics remain to be explored. This paper revisits cartographic design principles for 3D geospatial visualization and introduces an extended 3D semiotic model that complies with the general, interactive visualization pipeline. Based on this model, we propose NPR techniques to interactively synthesize cartographic renditions of basic feature types, such as terrain, water, and buildings. In particular, it includes a novel iconification concept to seamlessly interpolate between photorealistic and cartographic representations of 3D landmarks. Our work concludes with a discussion of open challenges in this field of research, including topics, such as user interaction and evaluation.}, language = {en} } @article{KunzeWeidlichWeske2015, author = {Kunze, Matthias and Weidlich, Matthias and Weske, Mathias}, title = {Querying process models by behavior inclusion}, series = {Software and systems modeling}, volume = {14}, journal = {Software and systems modeling}, number = {3}, publisher = {Springer}, address = {Heidelberg}, issn = {1619-1366}, doi = {10.1007/s10270-013-0389-6}, pages = {1105 -- 1125}, year = {2015}, abstract = {Business processes are vital to managing organizations as they sustain a company's competitiveness. Consequently, these organizations maintain collections of hundreds or thousands of process models for streamlining working procedures and facilitating process implementation. Yet, the management of large process model collections requires effective searching capabilities. Recent research focused on similarity search of process models, but querying process models is still a largely open topic. This article presents an approach to querying process models that takes a process example as input and discovers all models that allow replaying the behavior of the query. To this end, we provide a notion of behavioral inclusion that is based on trace semantics and abstraction. Additional to deciding a match, a closeness score is provided that describes how well the behavior of the query is represented in the model and can be used for ranking. The article introduces the formal foundations of the approach and shows how they are applied to querying large process model collections. An experimental evaluation has been conducted that confirms the suitability of the solution as well as its applicability and scalability in practice.}, language = {en} } @article{HerzbergMeyerWeske2015, author = {Herzberg, Nico and Meyer, Andreas and Weske, Mathias}, title = {Improving business process intelligence by observing object state transitions}, series = {Data \& knowledge engineering}, volume = {98}, journal = {Data \& knowledge engineering}, publisher = {Elsevier}, address = {Amsterdam}, issn = {0169-023X}, doi = {10.1016/j.datak.2015.07.008}, pages = {144 -- 164}, year = {2015}, abstract = {During the execution of business processes several events happen that are recorded in the company's information systems. These events deliver insights into process executions so that process monitoring and analysis can be performed resulting, for instance, in prediction of upcoming process steps or the analysis of the run time of single steps. While event capturing is trivial when a process engine with integrated logging capabilities is used, manual process execution environments do not provide automatic logging of events, so that typically external devices, like bar code scanners, have to be used. As experience shows, these manual steps are error-prone and induce additional work. Therefore, we use object state transitions as additional monitoring information, so-called object state transition events. Based on these object state transition events, we reason about the enablement and termination of activities and provide the basis for process monitoring and analysis in terms of a large event log. In this paper, we present the concept to utilize information from these object state transition events for capturing process progress. Furthermore, we discuss a methodology to create the required design time artifacts that then are used for monitoring at run time. In a proof-of-concept implementation, we show how the design time and run time side work and prove applicability of the introduced concept of object state transition events. (C) 2015 Elsevier B.V. All rights reserved.}, language = {en} } @article{BaumanBolzHirschfeldetal.2015, author = {Bauman, Spenser and Bolz, Carl Friedrich and Hirschfeld, Robert and Kirilichev, Vasily and Pape, Tobias and Siek, Jeremy G. and Tobin-Hochstadt, Sam}, title = {Pycket: A Tracing JIT for a Functional Language}, series = {ACM SIGPLAN notices}, volume = {50}, journal = {ACM SIGPLAN notices}, number = {9}, publisher = {Association for Computing Machinery}, address = {New York}, issn = {0362-1340}, doi = {10.1145/2784731.2784740}, pages = {22 -- 34}, year = {2015}, abstract = {We present Pycket, a high-performance tracing JIT compiler for Racket. Pycket supports a wide variety of the sophisticated features in Racket such as contracts, continuations, classes, structures, dynamic binding, and more. On average, over a standard suite of benchmarks, Pycket outperforms existing compilers, both Racket's JIT and other highly-optimizing Scheme compilers. Further, Pycket provides much better performance for Racket proxies than existing systems, dramatically reducing the overhead of contracts and gradual typing. We validate this claim with performance evaluation on multiple existing benchmark suites. The Pycket implementation is of independent interest as an application of the RPython meta-tracing framework (originally created for PyPy), which automatically generates tracing JIT compilers from interpreters. Prior work on meta-tracing focuses on bytecode interpreters, whereas Pycket is a high-level interpreter based on the CEK abstract machine and operates directly on abstract syntax trees. Pycket supports proper tail calls and first-class continuations. In the setting of a functional language, where recursion and higher-order functions are more prevalent than explicit loops, the most significant performance challenge for a tracing JIT is identifying which control flows constitute a loop-we discuss two strategies for identifying loops and measure their impact.}, language = {en} } @article{MeyerPufahlBatoulisetal.2015, author = {Meyer, Andreas and Pufahl, Luise and Batoulis, Kimon and Fahland, Dirk and Weske, Mathias}, title = {Automating data exchange in process choreographies}, series = {Information systems}, volume = {53}, journal = {Information systems}, publisher = {Elsevier}, address = {Oxford}, issn = {0306-4379}, doi = {10.1016/j.is.2015.03.008}, pages = {296 -- 329}, year = {2015}, abstract = {Communication between organizations is formalized as process choreographies in daily business. While the correct ordering of exchanged messages can be modeled and enacted with current choreography techniques, no approach exists to describe and automate the exchange of data between processes in a choreography using messages. This paper describes an entirely model-driven approach for BPMN introducing a few concepts that suffice to model data retrieval, data transformation, message exchange, and correlation four aspects of data exchange. For automation, this work utilizes a recent concept to enact data dependencies in internal processes. We present a modeling guideline to derive local process models from a given choreography; their operational semantics allows to correctly enact the entire choreography from the derived models only including the exchange of data. Targeting on successful interactions, we discuss means to ensure correct process choreography modeling. Finally, we implemented our approach by extending the camunda BPM platform with our approach and show its feasibility by realizing all service interaction patterns using only model-based concepts. (C) 2015 Elsevier Ltd. All rights reserved.}, language = {en} } @article{Schlosser2015, author = {Schlosser, Rainer}, title = {Dynamic pricing and advertising of perishable products with inventory holding costs}, series = {Journal of economic dynamics \& control}, volume = {57}, journal = {Journal of economic dynamics \& control}, publisher = {Elsevier}, address = {Amsterdam}, issn = {0165-1889}, doi = {10.1016/j.jedc.2015.05.017}, pages = {163 -- 181}, year = {2015}, abstract = {We examine a special class of dynamic pricing and advertising models for the sale of perishable goods, including marginal unit costs and inventory holding costs. The time horizon is assumed to be finite and we allow several model parameters to be dependent on time. For the stochastic version of the model, we derive closed-form expressions of the value function as well as of the optimal pricing and advertising policy in feedback form. Moreover, we show that for small unit shares, the model converges to a deterministic version of the problem, whose explicit solution is characterized by an overage and an underage case. We quantify the close relationship between the open-loop solution of the deterministic model and the expected evolution of optimally controlled stochastic sales processes. For both models, we derive sensitivity results. We find that in the case of positive holding costs, on average, optimal prices increase in time and advertising rates decrease. Furthermore, we analytically verify the excellent quality of optimal feedback policies of deterministic models applied in stochastic models. (C) 2015 Elsevier B.V. All rights reserved.}, language = {en} } @article{RoggeSoltiWeske2015, author = {Rogge-Solti, Andreas and Weske, Mathias}, title = {Prediction of business process durations using non-Markovian stochastic Petri nets}, series = {Information systems}, volume = {54}, journal = {Information systems}, publisher = {Elsevier}, address = {Oxford}, issn = {0306-4379}, doi = {10.1016/j.is.2015.04.004}, pages = {1 -- 14}, year = {2015}, abstract = {Companies need to efficiently manage their business processes to deliver products and services in time. Therefore, they monitor the progress of individual cases to be able to timely detect undesired deviations and to react accordingly. For example, companies can decide to speed up process execution by raising alerts or by using additional resources, which increases the chance that a certain deadline or service level agreement can be met. Central to such process control is accurate prediction of the remaining time of a case and the estimation of the risk of missing a deadline. To achieve this goal, we use a specific kind of stochastic Petri nets that can capture arbitrary duration distributions. Thereby, we are able to achieve higher prediction accuracy than related approaches. Further, we evaluate the approach in comparison to state of the art approaches and show the potential of exploiting a so far untapped source of information: the elapsed time since the last observed event. Real-world case studies in the financial and logistics domain serve to illustrate and evaluate the approach presented. (C) 2015 Elsevier Ltd. All rights reserved.}, language = {en} } @unpublished{OlivetoSutton2015, author = {Oliveto, Pietro S. and Sutton, Andrew M.}, title = {Editorial for the Special Issue on Theory of Evolutionary Algorithms 2014}, series = {Evolutionary computation}, volume = {23}, journal = {Evolutionary computation}, number = {4}, publisher = {MIT Press}, address = {Cambridge}, issn = {1063-6560}, doi = {10.1162/EVCO_e_00165}, pages = {509 -- 511}, year = {2015}, language = {en} } @article{FreudenbergIngallsFelgentreffetal.2015, author = {Freudenberg, Bert and Ingalls, Dan and Felgentreff, Tim and Pape, Tobias and Hirschfeld, Robert}, title = {SqueakJS A Modern and Practical Smalltalk that Runs in Any Browser}, series = {ACM SIGPLAN notices}, volume = {50}, journal = {ACM SIGPLAN notices}, number = {2}, publisher = {Association for Computing Machinery}, address = {New York}, issn = {0362-1340}, doi = {10.1145/10.1145/2661088.2661100}, pages = {57 -- 66}, year = {2015}, abstract = {We report our experience in implementing SqueakJS, a bitcompatible implementation of Squeak/Smalltalk written in pure JavaScript. SqueakJS runs entirely in theWeb browser with a virtual file system that can be directed to a server or client-side storage. Our implementation is notable for simplicity and performance gained through adaptation to the host object memory and deployment leverage gained through the Lively Web development environment. We present several novel techniques as well as performance measurements for the resulting virtual machine. Much of this experience is potentially relevant to preserving other dynamic language systems and making them available in a browser-based environment.}, language = {en} } @article{SteinertThamsenFelgentreffetal.2015, author = {Steinert, Bastian and Thamsen, Lauritz and Felgentreff, Tim and Hirschfeld, Robert}, title = {Object Versioning to Support Recovery Needs Using Proxies to Preserve Previous Development States in Lively}, series = {ACM SIGPLAN notices}, volume = {50}, journal = {ACM SIGPLAN notices}, number = {2}, publisher = {Association for Computing Machinery}, address = {New York}, issn = {0362-1340}, doi = {10.1145/2661088.2661093}, pages = {113 -- 124}, year = {2015}, abstract = {We present object versioning as a generic approach to preserve access to previous development and application states. Version-aware references can manage the modifications made to the target object and record versions as desired. Such references can be provided without modifications to the virtual machine. We used proxies to implement the proposed concepts and demonstrate the Lively Kernel running on top of this object versioning layer. This enables Lively users to undo the effects of direct manipulation and other programming actions.}, language = {en} } @article{NevesLeser2015, author = {Neves, Mariana and Leser, Ulf}, title = {Question answering for Biology}, series = {Methods : focusing on rapidly developing techniques}, volume = {74}, journal = {Methods : focusing on rapidly developing techniques}, publisher = {Elsevier}, address = {San Diego}, issn = {1046-2023}, doi = {10.1016/j.ymeth.2014.10.023}, pages = {36 -- 46}, year = {2015}, abstract = {Biologists often pose queries to search engines and biological databases to obtain answers related to ongoing experiments. This is known to be a time consuming, and sometimes frustrating, task in which more than one query is posed and many databases are consulted to come to possible answers for a single fact. Question answering comes as an alternative to this process by allowing queries to be posed as questions, by integrating various resources of different nature and by returning an exact answer to the user. We have surveyed the current solutions on question answering for Biology, present an overview on the methods which are usually employed and give insights on how to boost performance of systems in this domain. (C) 2014 Elsevier Inc. All rights reserved.}, language = {en} } @article{AzodiChengMeinel2015, author = {Azodi, Amir and Cheng, Feng and Meinel, Christoph}, title = {Event Driven Network Topology Discovery and Inventory Listing Using REAMS}, series = {Wireless personal communications : an international journal}, volume = {94}, journal = {Wireless personal communications : an international journal}, publisher = {Springer}, address = {New York}, issn = {0929-6212}, doi = {10.1007/s11277-015-3061-3}, pages = {415 -- 430}, year = {2015}, abstract = {Network Topology Discovery and Inventory Listing are two of the primary features of modern network monitoring systems (NMS). Current NMSs rely heavily on active scanning techniques for discovering and mapping network information. Although this approach works, it introduces some major drawbacks such as the performance impact it can exact, specially in larger network environments. As a consequence, scans are often run less frequently which can result in stale information being presented and used by the network monitoring system. Alternatively, some NMSs rely on their agents being deployed on the hosts they monitor. In this article, we present a new approach to Network Topology Discovery and Network Inventory Listing using only passive monitoring and scanning techniques. The proposed techniques rely solely on the event logs produced by the hosts and network devices present within a network. Finally, we discuss some of the advantages and disadvantages of our approach.}, language = {en} } @book{KunzeWeske2016, author = {Kunze, Matthias and Weske, Mathias}, title = {Behavioural Models}, publisher = {Springer}, address = {Cham}, isbn = {978-3-319-44958-6}, publisher = {Universit{\"a}t Potsdam}, pages = {279}, year = {2016}, abstract = {This textbook introduces the basis for modelling and analysing discrete dynamic systems, such as computer programmes, soft- and hardware systems, and business processes. The underlying concepts are introduced and concrete modelling techniques are described, such as finite automata, state machines, and Petri nets. The concepts are related to concrete application scenarios, among which business processes play a prominent role. The book consists of three parts, the first of which addresses the foundations of behavioural modelling. After a general introduction to modelling, it introduces transition systems as a basic formalism for representing the behaviour of discrete dynamic systems. This section also discusses causality, a fundamental concept for modelling and reasoning about behaviour. In turn, Part II forms the heart of the book and is devoted to models of behaviour. It details both sequential and concurrent systems and introduces finite automata, state machines and several different types of Petri nets. One chapter is especially devoted to business process models, workflow patterns and BPMN, the industry standard for modelling business processes. Lastly, Part III investigates how the behaviour of systems can be analysed. To this end, it introduces readers to the concept of state spaces. Further chapters cover the comparison of behaviour and the formal analysis and verification of behavioural models. The book was written for students of computer science and software engineering, as well as for programmers and system analysts interested in the behaviour of the systems they work on. It takes readers on a journey from the fundamentals of behavioural modelling to advanced techniques for modelling and analysing sequential and concurrent systems, and thus provides them a deep understanding of the concepts and techniques introduced and how they can be applied to concrete application scenarios.}, language = {en} } @article{DischerRichterDoellner2016, author = {Discher, S{\"o}ren and Richter, Rico and D{\"o}llner, J{\"u}rgen Roland Friedrich}, title = {Interactive and View-Dependent See-Through Lenses for Massive 3D Point Clouds}, series = {Advances in 3D Geoinformation}, journal = {Advances in 3D Geoinformation}, publisher = {Springer}, address = {Cham}, isbn = {978-3-319-25691-7}, issn = {1863-2246}, doi = {10.1007/978-3-319-25691-7_3}, pages = {49 -- 62}, year = {2016}, abstract = {3D point clouds are a digital representation of our world and used in a variety of applications. They are captured with LiDAR or derived by image-matching approaches to get surface information of objects, e.g., indoor scenes, buildings, infrastructures, cities, and landscapes. We present novel interaction and visualization techniques for heterogeneous, time variant, and semantically rich 3D point clouds. Interactive and view-dependent see-through lenses are introduced as exploration tools to enhance recognition of objects, semantics, and temporal changes within 3D point cloud depictions. We also develop filtering and highlighting techniques that are used to dissolve occlusion to give context-specific insights. All techniques can be combined with an out-of-core real-time rendering system for massive 3D point clouds. We have evaluated the presented approach with 3D point clouds from different application domains. The results show the usability and how different visualization and exploration tasks can be improved for a variety of domain-specific applications.}, language = {en} } @article{DoerrNeumannSutton2016, author = {Doerr, Benjamin and Neumann, Frank and Sutton, Andrew M.}, title = {Time Complexity Analysis of Evolutionary Algorithms on Random Satisfiable k-CNF Formulas}, series = {Algorithmica : an international journal in computer science}, volume = {78}, journal = {Algorithmica : an international journal in computer science}, publisher = {Springer}, address = {New York}, issn = {0178-4617}, doi = {10.1007/s00453-016-0190-3}, pages = {561 -- 586}, year = {2016}, abstract = {We contribute to the theoretical understanding of randomized search heuristics by investigating their optimization behavior on satisfiable random k-satisfiability instances both in the planted solution model and the uniform model conditional on satisfiability. Denoting the number of variables by n, our main technical result is that the simple () evolutionary algorithm with high probability finds a satisfying assignment in time when the clause-variable density is at least logarithmic. For low density instances, evolutionary algorithms seem to be less effective, and all we can show is a subexponential upper bound on the runtime for densities below . We complement these mathematical results with numerical experiments on a broader density spectrum. They indicate that, indeed, the () EA is less efficient on lower densities. Our experiments also suggest that the implicit constants hidden in our main runtime guarantee are low. Our main result extends and considerably improves the result obtained by Sutton and Neumann (Lect Notes Comput Sci 8672:942-951, 2014) in terms of runtime, minimum density, and clause length. These improvements are made possible by establishing a close fitness-distance correlation in certain parts of the search space. This approach might be of independent interest and could be useful for other average-case analyses of randomized search heuristics. While the notion of a fitness-distance correlation has been around for a long time, to the best of our knowledge, this is the first time that fitness-distance correlation is explicitly used to rigorously prove a performance statement for an evolutionary algorithm.}, language = {en} } @phdthesis{Wang2016, author = {Wang, Cheng}, title = {Deep Learning of Multimodal Representations}, school = {Universit{\"a}t Potsdam}, pages = {142}, year = {2016}, language = {en} } @misc{SerthPodlesnyBornsteinetal.2017, author = {Serth, Sebastian and Podlesny, Nikolai and Bornstein, Marvin and Lindemann, Jan and Latt, Johanna and Selke, Jan and Schlosser, Rainer and Boissier, Martin and Uflacker, Matthias}, title = {An interactive platform to simulate dynamic pricing competition on online marketplaces}, series = {2017 IEEE 21st International Enterprise Distributed Object Computing Conference (EDOC)}, journal = {2017 IEEE 21st International Enterprise Distributed Object Computing Conference (EDOC)}, publisher = {Institute of Electrical and Electronics Engineers}, address = {New York}, isbn = {978-1-5090-3045-3}, issn = {2325-6354}, doi = {10.1109/EDOC.2017.17}, pages = {61 -- 66}, year = {2017}, abstract = {E-commerce marketplaces are highly dynamic with constant competition. While this competition is challenging for many merchants, it also provides plenty of opportunities, e.g., by allowing them to automatically adjust prices in order to react to changing market situations. For practitioners however, testing automated pricing strategies is time-consuming and potentially hazardously when done in production. Researchers, on the other side, struggle to study how pricing strategies interact under heavy competition. As a consequence, we built an open continuous time framework to simulate dynamic pricing competition called Price Wars. The microservice-based architecture provides a scalable platform for large competitions with dozens of merchants and a large random stream of consumers. Our platform stores each event in a distributed log. This allows to provide different performance measures enabling users to compare profit and revenue of various repricing strategies in real-time. For researchers, price trajectories are shown which ease evaluating mutual price reactions of competing strategies. Furthermore, merchants can access historical marketplace data and apply machine learning. By providing a set of customizable, artificial merchants, users can easily simulate both simple rule-based strategies as well as sophisticated data-driven strategies using demand learning to optimize their pricing strategies.}, language = {en} } @article{SeiffertHolsteinSchlosseretal.2017, author = {Seiffert, Martin and Holstein, Flavio and Schlosser, Rainer and Schiller, Jochen}, title = {Next generation cooperative wearables}, series = {IEEE access : practical research, open solutions}, volume = {5}, journal = {IEEE access : practical research, open solutions}, publisher = {Institute of Electrical and Electronics Engineers}, address = {Piscataway}, issn = {2169-3536}, doi = {10.1109/ACCESS.2017.2749005}, pages = {16793 -- 16807}, year = {2017}, abstract = {Currently available wearables are usually based on a single sensor node with integrated capabilities for classifying different activities. The next generation of cooperative wearables could be able to identify not only activities, but also to evaluate them qualitatively using the data of several sensor nodes attached to the body, to provide detailed feedback for the improvement of the execution. Especially within the application domains of sports and health-care, such immediate feedback to the execution of body movements is crucial for (re-) learning and improving motor skills. To enable such systems for a broad range of activities, generalized approaches for human motion assessment within sensor networks are required. In this paper, we present a generalized trainable activity assessment chain (AAC) for the online assessment of periodic human activity within a wireless body area network. AAC evaluates the execution of separate movements of a prior trained activity on a fine-grained quality scale. We connect qualitative assessment with human knowledge by projecting the AAC on the hierarchical decomposition of motion performed by the human body as well as establishing the assessment on a kinematic evaluation of biomechanically distinct motion fragments. We evaluate AAC in a real-world setting and show that AAC successfully delimits the movements of correctly performed activity from faulty executions and provides detailed reasons for the activity assessment.}, language = {en} } @misc{LimbergerScheibelTrappetal.2017, author = {Limberger, Daniel and Scheibel, Willy and Trapp, Matthias and D{\"o}llner, J{\"u}rgen Roland Friedrich}, title = {Mixed-projection treemaps}, series = {21st International Conference Information Visualisation (IV)}, journal = {21st International Conference Information Visualisation (IV)}, publisher = {Institute of Electrical and Electronics Engineers}, address = {Los Alamitos}, isbn = {978-1-5386-0831-9}, issn = {2375-0138}, doi = {10.1109/iV.2017.67}, pages = {164 -- 169}, year = {2017}, abstract = {This paper presents a novel technique for combining 2D and 2.5D treemaps using multi-perspective views to leverage the advantages of both treemap types. It enables a new form of overview+detail visualization for tree-structured data and contributes new concepts for real-time rendering of and interaction with treemaps. The technique operates by tilting the graphical elements representing inner nodes using affine transformations and animated state transitions. We explain how to mix orthogonal and perspective projections within a single treemap. Finally, we show application examples that benefit from the reduced interaction overhead.}, language = {en} } @article{FelgentreffPerscheidHirschfeld2017, author = {Felgentreff, Tim and Perscheid, Michael and Hirschfeld, Robert}, title = {Implementing record and refinement for debugging timing-dependent communication}, series = {Science of computer programming}, volume = {134}, journal = {Science of computer programming}, publisher = {Elsevier}, address = {Amsterdam}, issn = {0167-6423}, doi = {10.1016/j.scico.2015.11.006}, pages = {4 -- 18}, year = {2017}, abstract = {Distributed applications are hard to debug because timing-dependent network communication is a source of non-deterministic behavior. Current approaches to debug non deterministic failures include post-mortem debugging as well as record and replay. However, the first impairs system performance to gather data, whereas the latter requires developers to understand the timing-dependent communication at a lower level of abstraction than they develop at. Furthermore, both approaches require intrusive core library modifications to gather data from live systems. In this paper, we present the Peek-At-Talk debugger for investigating non-deterministic failures with low overhead in a systematic, top-down method, with a particular focus on tool-building issues in the following areas: First, we show how our debugging framework Path Tools guides developers from failures to their root causes and gathers run-time data with low overhead. Second, we present Peek-At-Talk, an extension to our Path Tools framework to record non-deterministic communication and refine behavioral data that connects source code with network events. Finally, we scope changes to the core library to record network communication without impacting other network applications.}, language = {en} } @misc{Giese2017, author = {Giese, Holger}, title = {Formal models and analysis for self-adaptive cyber-physical systems}, series = {Lecture notes in computer science}, volume = {10231}, journal = {Lecture notes in computer science}, editor = {Kouchnarenko, Olga and Khosravi, Ramtin}, publisher = {Springer}, address = {Cham}, isbn = {978-3-319-57666-4}, issn = {0302-9743}, doi = {10.1007/978-3-319-57666-4_1}, pages = {3 -- 9}, year = {2017}, abstract = {In this extended abstract, we will analyze the current challenges for the envisioned Self-Adaptive CPS. In addition, we will outline our results to approach these challenges with SMARTSOS [10] a generic approach based on extensions of graph transformation systems employing open and adaptive collaborations and models at runtime for trustworthy self-adaptation, self-organization, and evolution of the individual systems and the system-of-systems level taking the independent development, operation, management, and evolution of these systems into account.}, language = {en} } @article{HartigPirro2017, author = {Hartig, Olaf and Pirr{\`o}, Giuseppe}, title = {SPARQL with property paths on the Web}, series = {Semantic web}, volume = {8}, journal = {Semantic web}, number = {6}, publisher = {IOS Press}, address = {Amsterdam}, issn = {1570-0844}, doi = {10.3233/SW-160237}, pages = {773 -- 795}, year = {2017}, abstract = {Linked Data on the Web represents an immense source of knowledge suitable to be automatically processed and queried. In this respect, there are different approaches for Linked Data querying that differ on the degree of centralization adopted. On one hand, the SPARQL query language, originally defined for querying single datasets, has been enhanced with features to query federations of datasets; however, this attempt is not sufficient to cope with the distributed nature of data sources available as Linked Data. On the other hand, extensions or variations of SPARQL aim to find trade-offs between centralized and fully distributed querying. The idea is to partially move the computational load from the servers to the clients. Despite the variety and the relative merits of these approaches, as of today, there is no standard language for querying Linked Data on theWeb. A specific requirement for such a language to capture the distributed, graph-like nature of Linked Data sources on the Web is a support of graph navigation. Recently, SPARQL has been extended with a navigational feature called property paths (PPs). However, the semantics of SPARQL restricts the scope of navigation via PPs to single RDF graphs. This restriction limits the applicability of PPs for querying distributed Linked Data sources on the Web. To fill this gap, in this paper we provide formal foundations for evaluating PPs on the Web, thus contributing to the definition of a query language for Linked Data. We first introduce a family of reachability-based query semantics for PPs that distinguish between navigation on the Web and navigation at the data level. Thereafter, we consider another, alternative query semantics that couples Web graph navigation and data level navigation; we call it context-based semantics. Given these semantics, we find that for some PP-based SPARQL queries a complete evaluation on the Web is not possible. To study this phenomenon we introduce a notion of Web-safeness of queries, and prove a decidable syntactic property that enables systems to identify queries that areWeb-safe. In addition to establishing these formal foundations, we conducted an experimental comparison of the context-based semantics and a reachability- based semantics. Our experiments show that when evaluating a PP-based query under the context-based semantics one experiences a significantly smaller number of dereferencing operations, but the computed query result may contain less solutions.}, language = {en} } @inproceedings{SchlosserBoissier2017, author = {Schlosser, Rainer and Boissier, Martin}, title = {Optimal price reaction strategies in the presence of active and passive competitors}, series = {Proceedings of the 6th International Conference on Operations Research and Enterprise Systems - ICORES}, booktitle = {Proceedings of the 6th International Conference on Operations Research and Enterprise Systems - ICORES}, editor = {Liberatore, Federico and Parlier, Greg H. and Demange, Marc}, publisher = {SCITEPRESS - Science and Technology Publications, Lda.}, address = {Set{\´u}bal}, isbn = {978-989-758-218-9}, doi = {10.5220/0006118200470056}, pages = {47 -- 56}, year = {2017}, abstract = {Many markets are characterized by pricing competition. Typically, competitors are involved that adjust their prices in response to other competitors with different frequencies. We analyze stochastic dynamic pricing models under competition for the sale of durable goods. Given a competitor's pricing strategy, we show how to derive optimal response strategies that take the anticipated competitor's price adjustments into account. We study resulting price cycles and the associated expected long-term profits. We show that reaction frequencies have a major impact on a strategy's performance. In order not to act predictable our model also allows to include randomized reaction times. Additionally, we study to which extent optimal response strategies of active competitors are affected by additional passive competitors that use constant prices. It turns out that optimized feedback strategies effectively avoid a decline in price. They help to gain profits, especially, when aggressive competitor s are involved.}, language = {en} } @misc{PlauthSterzEberhardtetal.2017, author = {Plauth, Max and Sterz, Christoph and Eberhardt, Felix and Feinbube, Frank and Polze, Andreas}, title = {Assessing NUMA performance based on hardware event counters}, series = {IEEE International Parallel and Distributed Processing Symposium Workshops (IPDPSW)}, journal = {IEEE International Parallel and Distributed Processing Symposium Workshops (IPDPSW)}, publisher = {Institute of Electrical and Electronics Engineers}, address = {New York}, isbn = {978-0-7695-6149-3}, issn = {2164-7062}, doi = {10.1109/IPDPSW.2017.51}, pages = {904 -- 913}, year = {2017}, abstract = {Cost models play an important role for the efficient implementation of software systems. These models can be embedded in operating systems and execution environments to optimize execution at run time. Even though non-uniform memory access (NUMA) architectures are dominating today's server landscape, there is still a lack of parallel cost models that represent NUMA system sufficiently. Therefore, the existing NUMA models are analyzed, and a two-step performance assessment strategy is proposed that incorporates low-level hardware counters as performance indicators. To support the two-step strategy, multiple tools are developed, all accumulating and enriching specific hardware event counter information, to explore, measure, and visualize these low-overhead performance indicators. The tools are showcased and discussed alongside specific experiments in the realm of performance assessment.}, language = {en} } @misc{LorenzKiekhebenSchnor2017, author = {Lorenz, Claas and Kiekheben, Sebastian and Schnor, Bettina}, title = {FaVe: Modeling IPv6 firewalls for fast formal verification}, series = {International Conference on Networked Systems (NetSys) 2017}, journal = {International Conference on Networked Systems (NetSys) 2017}, publisher = {IEEE}, address = {New York}, doi = {10.1109/NetSys.2017.7903956}, pages = {8}, year = {2017}, abstract = {As virtualization drives the automation of networking, the validation of security properties becomes more and more challenging eventually ruling out manual inspections. While formal verification in Software Defined Networks is provided by comprehensive tools with high speed reverification capabilities like NetPlumber for instance, the presence of middlebox functionality like firewalls is not considered. Also, they lack the ability to handle dynamic protocol elements like IPv6 extension header chains. In this work, we provide suitable modeling abstractions to enable both - the inclusion of firewalls and dynamic protocol elements. We exemplarily model the Linux ip6tables/netfilter packet filter and also provide abstractions for an application layer gateway. Finally, we present a prototype of our formal verification system FaVe.}, language = {en} } @article{SapeginJaegerChengetal.2017, author = {Sapegin, Andrey and Jaeger, David and Cheng, Feng and Meinel, Christoph}, title = {Towards a system for complex analysis of security events in large-scale networks}, series = {Computers \& security : the international journal devoted to the study of the technical and managerial aspects of computer security}, volume = {67}, journal = {Computers \& security : the international journal devoted to the study of the technical and managerial aspects of computer security}, publisher = {Elsevier Science}, address = {Oxford}, issn = {0167-4048}, doi = {10.1016/j.cose.2017.02.001}, pages = {16 -- 34}, year = {2017}, abstract = {After almost two decades of development, modern Security Information and Event Management (SIEM) systems still face issues with normalisation of heterogeneous data sources, high number of false positive alerts and long analysis times, especially in large-scale networks with high volumes of security events. In this paper, we present our own prototype of SIEM system, which is capable of dealing with these issues. For efficient data processing, our system employs in-memory data storage (SAP HANA) and our own technologies from the previous work, such as the Object Log Format (OLF) and high-speed event normalisation. We analyse normalised data using a combination of three different approaches for security analysis: misuse detection, query-based analytics, and anomaly detection. Compared to the previous work, we have significantly improved our unsupervised anomaly detection algorithms. Most importantly, we have developed a novel hybrid outlier detection algorithm that returns ranked clusters of anomalies. It lets an operator of a SIEM system to concentrate on the several top-ranked anomalies, instead of digging through an unsorted bundle of suspicious events. We propose to use anomaly detection in a combination with signatures and queries, applied on the same data, rather than as a full replacement for misuse detection. In this case, the majority of attacks will be captured with misuse detection, whereas anomaly detection will highlight previously unknown behaviour or attacks. We also propose that only the most suspicious event clusters need to be checked by an operator, whereas other anomalies, including false positive alerts, do not need to be explicitly checked if they have a lower ranking. We have proved our concepts and algorithms on a dataset of 160 million events from a network segment of a big multinational company and suggest that our approach and methods are highly relevant for modern SIEM systems.}, language = {en} } @article{ChujfiLaRocheMeinel2017, author = {Chujfi-La-Roche, Salim and Meinel, Christoph}, title = {Matching cognitively sympathetic individual styles to develop collective intelligence in digital communities}, series = {AI \& society : the journal of human-centred systems and machine intelligence}, volume = {35}, journal = {AI \& society : the journal of human-centred systems and machine intelligence}, number = {1}, publisher = {Springer}, address = {New York}, issn = {0951-5666}, doi = {10.1007/s00146-017-0780-x}, pages = {5 -- 15}, year = {2017}, abstract = {Creation, collection and retention of knowledge in digital communities is an activity that currently requires being explicitly targeted as a secure method of keeping intellectual capital growing in the digital era. In particular, we consider it relevant to analyze and evaluate the empathetic cognitive personalities and behaviors that individuals now have with the change from face-to-face communication (F2F) to computer-mediated communication (CMC) online. This document proposes a cyber-humanistic approach to enhance the traditional SECI knowledge management model. A cognitive perception is added to its cyclical process following design thinking interaction, exemplary for improvement of the method in which knowledge is continuously created, converted and shared. In building a cognitive-centered model, we specifically focus on the effective identification and response to cognitive stimulation of individuals, as they are the intellectual generators and multiplicators of knowledge in the online environment. Our target is to identify how geographically distributed-digital-organizations should align the individual's cognitive abilities to promote iteration and improve interaction as a reliable stimulant of collective intelligence. The new model focuses on analyzing the four different stages of knowledge processing, where individuals with sympathetic cognitive personalities can significantly boost knowledge creation in a virtual social system. For organizations, this means that multidisciplinary individuals can maximize their extensive potential, by externalizing their knowledge in the correct stage of the knowledge creation process, and by collaborating with their appropriate sympathetically cognitive remote peers.}, language = {en} } @misc{MalchowRenzBaueretal.2017, author = {Malchow, Martin and Renz, Jan and Bauer, Matthias and Meinel, Christoph}, title = {Embedded smart home}, series = {11th Annual IEEE International Systems Conference (SysCon)}, journal = {11th Annual IEEE International Systems Conference (SysCon)}, publisher = {IEEE}, address = {New York}, isbn = {978-1-5090-4623-2}, issn = {1944-7620}, doi = {10.1109/SYSCON.2017.7934728}, pages = {195 -- 200}, year = {2017}, abstract = {The popularity of MOOCs has increased considerably in the last years. A typical MOOC course consists of video content, self tests after a video and homework, which is normally in multiple choice format. After solving this homeworks for every week of a MOOC, the final exam certificate can be issued when the student has reached a sufficient score. There are also some attempts to include practical tasks, such as programming, in MOOCs for grading. Nevertheless, until now there is no known possibility to teach embedded system programming in a MOOC course where the programming can be done in a remote lab and where grading of the tasks is additionally possible. This embedded programming includes communication over GPIO pins to control LEDs and measure sensor values. We started a MOOC course called "Embedded Smart Home" as a pilot to prove the concept to teach real hardware programming in a MOOC environment under real life MOOC conditions with over 6000 students. Furthermore, also students with real hardware have the possibility to program on their own real hardware and grade their results in the MOOC course. Finally, we evaluate our approach and analyze the student acceptance of this approach to offer a course on embedded programming. We also analyze the hardware usage and working time of students solving tasks to find out if real hardware programming is an advantage and motivating achievement to support students learning success.}, language = {en} } @misc{AlibabaieGhasemzadehMeinel2017, author = {Alibabaie, Najmeh and Ghasemzadeh, Mohammad and Meinel, Christoph}, title = {A variant of genetic algorithm for non-homogeneous population}, series = {International Conference Applied Mathematics, Computational Science and Systems Engineering 2016}, volume = {9}, journal = {International Conference Applied Mathematics, Computational Science and Systems Engineering 2016}, publisher = {EDP Sciences}, address = {Les Ulis}, issn = {2271-2097}, doi = {10.1051/itmconf/20170902001}, pages = {8}, year = {2017}, abstract = {Selection of initial points, the number of clusters and finding proper clusters centers are still the main challenge in clustering processes. In this paper, we suggest genetic algorithm based method which searches several solution spaces simultaneously. The solution spaces are population groups consisting of elements with similar structure. Elements in a group have the same size, while elements in different groups are of different sizes. The proposed algorithm processes the population in groups of chromosomes with one gene, two genes to k genes. These genes hold corresponding information about the cluster centers. In the proposed method, the crossover and mutation operators can accept parents with different sizes; this can lead to versatility in population and information transfer among sub-populations. We implemented the proposed method and evaluated its performance against some random datasets and the Ruspini dataset as well. The experimental results show that the proposed method could effectively determine the appropriate number of clusters and recognize their centers. Overall this research implies that using heterogeneous population in the genetic algorithm can lead to better results.}, language = {en} } @misc{GawronChengMeinel2017, author = {Gawron, Marian and Cheng, Feng and Meinel, Christoph}, title = {PVD: Passive Vulnerability Detection}, series = {8th International Conference on Information and Communication Systems (ICICS)}, journal = {8th International Conference on Information and Communication Systems (ICICS)}, publisher = {IEEE}, address = {New York}, isbn = {978-1-5090-4243-2}, issn = {2471-125X}, doi = {10.1109/IACS.2017.7921992}, pages = {322 -- 327}, year = {2017}, abstract = {The identification of vulnerabilities relies on detailed information about the target infrastructure. The gathering of the necessary information is a crucial step that requires an intensive scanning or mature expertise and knowledge about the system even though the information was already available in a different context. In this paper we propose a new method to detect vulnerabilities that reuses the existing information and eliminates the necessity of a comprehensive scan of the target system. Since our approach is able to identify vulnerabilities without the additional effort of a scan, we are able to increase the overall performance of the detection. Because of the reuse and the removal of the active testing procedures, our approach could be classified as a passive vulnerability detection. We will explain the approach and illustrate the additional possibility to increase the security awareness of users. Therefore, we applied the approach on an experimental setup and extracted security relevant information from web logs.}, language = {en} } @misc{TorkuraSukmanaChengetal.2017, author = {Torkura, Kennedy A. and Sukmana, Muhammad Ihsan Haikal and Cheng, Feng and Meinel, Christoph}, title = {Leveraging cloud native design patterns for security-as-a-service applications}, series = {IEEE International Conference on Smart Cloud (SmartCloud)}, journal = {IEEE International Conference on Smart Cloud (SmartCloud)}, publisher = {Institute of Electrical and Electronics Engineers}, address = {New York}, isbn = {978-1-5386-3684-8}, doi = {10.1109/SmartCloud.2017.21}, pages = {90 -- 97}, year = {2017}, abstract = {This paper discusses a new approach for designing and deploying Security-as-a-Service (SecaaS) applications using cloud native design patterns. Current SecaaS approaches do not efficiently handle the increasing threats to computer systems and applications. For example, requests for security assessments drastically increase after a high-risk security vulnerability is disclosed. In such scenarios, SecaaS applications are unable to dynamically scale to serve requests. A root cause of this challenge is employment of architectures not specifically fitted to cloud environments. Cloud native design patterns resolve this challenge by enabling certain properties e.g. massive scalability and resiliency via the combination of microservice patterns and cloud-focused design patterns. However adopting these patterns is a complex process, during which several security issues are introduced. In this work, we investigate these security issues, we redesign and deploy a monolithic SecaaS application using cloud native design patterns while considering appropriate, layered security counter-measures i.e. at the application and cloud networking layer. Our prototype implementation out-performs traditional, monolithic applications with an average Scanner Time of 6 minutes, without compromising security. Our approach can be employed for designing secure, scalable and performant SecaaS applications that effectively handle unexpected increase in security assessment requests.}, language = {en} } @article{OmotoshoEmuoyibofarheMeinel2017, author = {Omotosho, Adebayo and Emuoyibofarhe, Justice and Meinel, Christoph}, title = {Securing e-prescription from medical identity theft using steganography and antiphishing techniques}, series = {Journal of applied security research}, volume = {12}, journal = {Journal of applied security research}, publisher = {Routledge, Taylor \& Francis Group}, address = {Philadelphia}, issn = {1936-1610}, doi = {10.1080/19361610.2017.1315788}, pages = {447 -- 461}, year = {2017}, abstract = {Drug prescription is among the health care process that usually makes references to the patients' medical and insurance information among other personal data, because this information is very vital and delicate, it should be adequately protected from identity thieves. This article aims at securing Electronic Prescription (EP) in order to minimize patient's data theft and foster patients' trust of EP system. This paper presents a steganography and antiphishing technique for preventing medical identity theft in EP. The proposed EP system design focused on the security features in the prescriber and dispensers' modules of EP by ensuring the prescriber sends the prescription of the patient in a safe manner and to the right dispenser without the interference of fake third parties. Hexadecimal steganography image system is used to cover and secure the sent prescription details. Malicious electronic dispensing system is prevented through an authentication technique where a dispenser uses a captcha together with a one-time password, and the web server encrypted token for prescriber's device authentication. The steganography system is evaluated using Peak Signal to Noise Ratio (PSNR). The system implementation results showed that steganography and antiphishing techniques are capable of providing a secure EP systems.}, language = {en} } @misc{StaubitzWilkinsHagedornetal.2017, author = {Staubitz, Thomas and Wilkins, Christian and Hagedorn, Christiane and Meinel, Christoph}, title = {The Gamification of a MOOC Platform}, series = {Proceedings of 2017 IEEE Global Engineering Education Conference (EDUCON)}, journal = {Proceedings of 2017 IEEE Global Engineering Education Conference (EDUCON)}, publisher = {IEEE}, address = {New York}, isbn = {978-1-5090-5467-1}, issn = {2165-9567}, doi = {10.1109/EDUCON.2017.7942952}, pages = {883 -- 892}, year = {2017}, abstract = {Massive Open Online Courses (MOOCs) have left their mark on the face of education during the recent years. At the Hasso Plattner Institute (HPI) in Potsdam, Germany, we are actively developing a MOOC platform, which provides our research with a plethora of e-learning topics, such as learning analytics, automated assessment, peer assessment, team-work, online proctoring, and gamification. We run several instances of this platform. On openHPI, we provide our own courses from within the HPI context. Further instances are openSAP, openWHO, and mooc.HOUSE, which is the smallest of these platforms, targeting customers with a less extensive course portfolio. In 2013, we started to work on the gamification of our platform. By now, we have implemented about two thirds of the features that we initially have evaluated as useful for our purposes. About a year ago we activated the implemented gamification features on mooc.HOUSE. Before activating the features on openHPI as well, we examined, and re-evaluated our initial considerations based on the data we collected so far and the changes in other contexts of our platforms.}, language = {en} } @article{PengLiuWangetal.2018, author = {Peng, Junjie and Liu, Danxu and Wang, Yingtao and Zeng, Ying and Cheng, Feng and Zhang, Wenqiang}, title = {Weight-based strategy for an I/O-intensive application at a cloud data center}, series = {Concurrency and computation : practice \& experience}, volume = {30}, journal = {Concurrency and computation : practice \& experience}, number = {19}, publisher = {Wiley}, address = {Hoboken}, issn = {1532-0626}, doi = {10.1002/cpe.4648}, pages = {14}, year = {2018}, abstract = {Applications with different characteristics in the cloud may have different resources preferences. However, traditional resource allocation and scheduling strategies rarely take into account the characteristics of applications. Considering that an I/O-intensive application is a typical type of application and that frequent I/O accesses, especially small files randomly accessing the disk, may lead to an inefficient use of resources and reduce the quality of service (QoS) of applications, a weight allocation strategy is proposed based on the available resources that a physical server can provide as well as the characteristics of the applications. Using the weight obtained, a resource allocation and scheduling strategy is presented based on the specific application characteristics in the data center. Extensive experiments show that the strategy is correct and can guarantee a high concurrency of I/O per second (IOPS) in a cloud data center with high QoS. Additionally, the strategy can efficiently improve the utilization of the disk and resources of the data center without affecting the service quality of applications.}, language = {en} } @article{KoehlerKoehlerDeckwartetal.2018, author = {Koehler, Friedrich and Koehler, Kerstin and Deckwart, Oliver and Prescher, Sandra and Wegscheider, Karl and Winkler, Sebastian and Vettorazzi, Eik and Polze, Andreas and Stangl, Karl and Hartmann, Oliver and Marx, Almuth and Neuhaus, Petra and Scherf, Michael and Kirwan, Bridget-Anne and Anker, Stefan D.}, title = {Telemedical Interventional Management in Heart Failure II (TIM-HF2), a randomised, controlled trial investigating the impact of telemedicine on unplanned cardiovascular hospitalisations and mortality in heart failure patients}, series = {European Journal of Heart Failure}, volume = {20}, journal = {European Journal of Heart Failure}, number = {10}, publisher = {Wiley}, address = {Hoboken}, issn = {1388-9842}, doi = {10.1002/ejhf.1300}, pages = {1485 -- 1493}, year = {2018}, abstract = {Background Heart failure (HF) is a complex, chronic condition that is associated with debilitating symptoms, all of which necessitate close follow-up by health care providers. Lack of disease monitoring may result in increased mortality and more frequent hospital readmissions for decompensated HF. Remote patient management (RPM) in this patient population may help to detect early signs and symptoms of cardiac decompensation, thus enabling a prompt initiation of the appropriate treatment and care before a manifestation of HF decompensation. Objective The objective of the present article is to describe the design of a new trial investigating the impact of RPM on unplanned cardiovascular hospitalisations and mortality in HF patients. Methods The TIM-HF2 trial is designed as a prospective, randomised, controlled, parallel group, open (with randomisation concealment), multicentre trial with pragmatic elements introduced for data collection. Eligible patients with HF are randomised (1:1) to either RPM + usual care or to usual care only and are followed for 12 months. The primary outcome is the percentage of days lost due to unplanned cardiovascular hospitalisations or all-cause death. The main secondary outcomes are all-cause and cardiovascular mortality. Conclusion The TIM-HF2 trial will provide important prospective data on the potential beneficial effect of telemedical monitoring and RPM on unplanned cardiovascular hospitalisations and mortality in HF patients.}, language = {en} } @article{MendlingWebervanderAalstetal.2018, author = {Mendling, Jan and Weber, Ingo and van der Aalst, Wil and Brocke, Jan Vom and Cabanillas, Cristina and Daniel, Florian and Debois, Soren and Di Ciccio, Claudio and Dumas, Marlon and Dustdar, Schahram and Gal, Avigdor and Garcia-Banuelos, Luciano and Governatori, Guido and Hull, Richard and La Rosa, Marcello and Leopold, Henrik and Leymann, Frank and Recker, Jan and Reichert, Manfred and Reijers, Hajo A. and Rinderle-Ma, Stefanie and Solti, Andreas and Rosemann, Michael and Schulte, Stefan and Singh, Munindar P. and Slaats, Tijs and Staples, Mark and Weber, Barbara and Weidlich, Matthias and Weske, Mathias and Xu, Xiwei and Zhu, Liming}, title = {Blockchains for Business Process Management}, series = {ACM Transactions on Management Information Systems}, volume = {9}, journal = {ACM Transactions on Management Information Systems}, number = {1}, publisher = {Association for Computing Machinery}, address = {New York}, issn = {2158-656X}, doi = {10.1145/3183367}, pages = {1 -- 16}, year = {2018}, abstract = {Blockchain technology offers a sizable promise to rethink the way interorganizational business processes are managed because of its potential to realize execution without a central party serving as a single point of trust (and failure). To stimulate research on this promise and the limits thereof, in this article, we outline the challenges and opportunities of blockchain for business process management (BPM). We first reflect how blockchains could be used in the context of the established BPM lifecycle and second how they might become relevant beyond. We conclude our discourse with a summary of seven research directions for investigating the application of blockchain technology in the context of BPM.}, language = {en} } @misc{StojanovicTrappRichteretal.2018, author = {Stojanovic, Vladeta and Trapp, Matthias and Richter, Rico and D{\"o}llner, J{\"u}rgen Roland Friedrich}, title = {A service-oriented approach for classifying 3D points clouds by example of office furniture classification}, series = {Web3D 2018: Proceedings of the 23rd International ACM Conference on 3D Web Technology}, journal = {Web3D 2018: Proceedings of the 23rd International ACM Conference on 3D Web Technology}, publisher = {Association for Computing Machinery}, address = {New York}, isbn = {978-1-4503-5800-2}, doi = {10.1145/3208806.3208810}, pages = {1 -- 9}, year = {2018}, abstract = {The rapid digitalization of the Facility Management (FM) sector has increased the demand for mobile, interactive analytics approaches concerning the operational state of a building. These approaches provide the key to increasing stakeholder engagement associated with Operation and Maintenance (O\&M) procedures of living and working areas, buildings, and other built environment spaces. We present a generic and fast approach to process and analyze given 3D point clouds of typical indoor office spaces to create corresponding up-to-date approximations of classified segments and object-based 3D models that can be used to analyze, record and highlight changes of spatial configurations. The approach is based on machine-learning methods used to classify the scanned 3D point cloud data using 2D images. This approach can be used to primarily track changes of objects over time for comparison, allowing for routine classification, and presentation of results used for decision making. We specifically focus on classification, segmentation, and reconstruction of multiple different object types in a 3D point-cloud scene. We present our current research and describe the implementation of these technologies as a web-based application using a services-oriented methodology.}, language = {en} } @article{KoumarelasKroschkMosleyetal.2018, author = {Koumarelas, Ioannis and Kroschk, Axel and Mosley, Clifford and Naumann, Felix}, title = {Experience: Enhancing address matching with geocoding and similarity measure selection}, series = {Journal of Data and Information Quality}, volume = {10}, journal = {Journal of Data and Information Quality}, number = {2}, publisher = {Association for Computing Machinery}, address = {New York}, issn = {1936-1955}, doi = {10.1145/3232852}, pages = {1 -- 16}, year = {2018}, abstract = {Given a query record, record matching is the problem of finding database records that represent the same real-world object. In the easiest scenario, a database record is completely identical to the query. However, in most cases, problems do arise, for instance, as a result of data errors or data integrated from multiple sources or received from restrictive form fields. These problems are usually difficult, because they require a variety of actions, including field segmentation, decoding of values, and similarity comparisons, each requiring some domain knowledge. In this article, we study the problem of matching records that contain address information, including attributes such as Street-address and City. To facilitate this matching process, we propose a domain-specific procedure to, first, enrich each record with a more complete representation of the address information through geocoding and reverse-geocoding and, second, to select the best similarity measure per each address attribute that will finally help the classifier to achieve the best f-measure. We report on our experience in selecting geocoding services and discovering similarity measures for a concrete but common industry use-case.}, language = {en} } @article{SchneiderLambersOrejas2018, author = {Schneider, Sven and Lambers, Leen and Orejas, Fernando}, title = {Automated reasoning for attributed graph properties}, series = {International Journal on Software Tools for Technology Transfer}, volume = {20}, journal = {International Journal on Software Tools for Technology Transfer}, number = {6}, publisher = {Springer}, address = {Heidelberg}, issn = {1433-2779}, doi = {10.1007/s10009-018-0496-3}, pages = {705 -- 737}, year = {2018}, abstract = {Graphs are ubiquitous in computer science. Moreover, in various application fields, graphs are equipped with attributes to express additional information such as names of entities or weights of relationships. Due to the pervasiveness of attributed graphs, it is highly important to have the means to express properties on attributed graphs to strengthen modeling capabilities and to enable analysis. Firstly, we introduce a new logic of attributed graph properties, where the graph part and attribution part are neatly separated. The graph part is equivalent to first-order logic on graphs as introduced by Courcelle. It employs graph morphisms to allow the specification of complex graph patterns. The attribution part is added to this graph part by reverting to the symbolic approach to graph attribution, where attributes are represented symbolically by variables whose possible values are specified by a set of constraints making use of algebraic specifications. Secondly, we extend our refutationally complete tableau-based reasoning method as well as our symbolic model generation approach for graph properties to attributed graph properties. Due to the new logic mentioned above, neatly separating the graph and attribution parts, and the categorical constructions employed only on a more abstract level, we can leave the graph part of the algorithms seemingly unchanged. For the integration of the attribution part into the algorithms, we use an oracle, allowing for flexible adoption of different available SMT solvers in the actual implementation. Finally, our automated reasoning approach for attributed graph properties is implemented in the tool AutoGraph integrating in particular the SMT solver Z3 for the attribute part of the properties. We motivate and illustrate our work with a particular application scenario on graph database query validation.}, language = {en} } @article{FriedrichKatzmannKrohmer2018, author = {Friedrich, Tobias and Katzmann, Maximilian and Krohmer, Anton}, title = {Unbounded Discrepancy of Deterministic Random Walks on Grids}, series = {SIAM journal on discrete mathematics}, volume = {32}, journal = {SIAM journal on discrete mathematics}, number = {4}, publisher = {Society for Industrial and Applied Mathematics}, address = {Philadelphia}, issn = {0895-4801}, doi = {10.1137/17M1131088}, pages = {2441 -- 2452}, year = {2018}, abstract = {Random walks are frequently used in randomized algorithms. We study a derandomized variant of a random walk on graphs called the rotor-router model. In this model, instead of distributing tokens randomly, each vertex serves its neighbors in a fixed deterministic order. For most setups, both processes behave in a remarkably similar way: Starting with the same initial configuration, the number of tokens in the rotor-router model deviates only slightly from the expected number of tokens on the corresponding vertex in the random walk model. The maximal difference over all vertices and all times is called single vertex discrepancy. Cooper and Spencer [Combin. Probab. Comput., 15 (2006), pp. 815-822] showed that on Z(d), the single vertex discrepancy is only a constant c(d). Other authors also determined the precise value of c(d) for d = 1, 2. All of these results, however, assume that initially all tokens are only placed on one partition of the bipartite graph Z(d). We show that this assumption is crucial by proving that, otherwise, the single vertex discrepancy can become arbitrarily large. For all dimensions d >= 1 and arbitrary discrepancies l >= 0, we construct configurations that reach a discrepancy of at least l.}, language = {en} } @article{WangYangMeinel2018, author = {Wang, Cheng and Yang, Haojin and Meinel, Christoph}, title = {Image Captioning with Deep Bidirectional LSTMs and Multi-Task Learning}, series = {ACM transactions on multimedia computing, communications, and applications}, volume = {14}, journal = {ACM transactions on multimedia computing, communications, and applications}, number = {2}, publisher = {Association for Computing Machinery}, address = {New York}, issn = {1551-6857}, doi = {10.1145/3115432}, pages = {20}, year = {2018}, abstract = {Generating a novel and descriptive caption of an image is drawing increasing interests in computer vision, natural language processing, and multimedia communities. In this work, we propose an end-to-end trainable deep bidirectional LSTM (Bi-LSTM (Long Short-Term Memory)) model to address the problem. By combining a deep convolutional neural network (CNN) and two separate LSTM networks, our model is capable of learning long-term visual-language interactions by making use of history and future context information at high-level semantic space. We also explore deep multimodal bidirectional models, in which we increase the depth of nonlinearity transition in different ways to learn hierarchical visual-language embeddings. Data augmentation techniques such as multi-crop, multi-scale, and vertical mirror are proposed to prevent over-fitting in training deep models. To understand how our models "translate" image to sentence, we visualize and qualitatively analyze the evolution of Bi-LSTM internal states over time. The effectiveness and generality of proposed models are evaluated on four benchmark datasets: Flickr8K, Flickr30K, MSCOCO, and Pascal1K datasets. We demonstrate that Bi-LSTM models achieve highly competitive performance on both caption generation and image-sentence retrieval even without integrating an additional mechanism (e.g., object detection, attention model). Our experiments also prove that multi-task learning is beneficial to increase model generality and gain performance. We also demonstrate the performance of transfer learning of the Bi-LSTM model significantly outperforms previous methods on the Pascal1K dataset.}, language = {en} } @article{CabalarKaminskiSchaubetal.2018, author = {Cabalar, Pedro and Kaminski, Roland and Schaub, Torsten and Schuhmann, Anna}, title = {Temporal answer set programming on finite traces}, series = {Theory and practice of logic programming}, volume = {18}, journal = {Theory and practice of logic programming}, number = {3-4}, publisher = {Cambridge Univ. Press}, address = {New York}, issn = {1471-0684}, doi = {10.1017/S1471068418000297}, pages = {406 -- 420}, year = {2018}, abstract = {In this paper, we introduce an alternative approach to Temporal Answer Set Programming that relies on a variation of Temporal Equilibrium Logic (TEL) for finite traces. This approach allows us to even out the expressiveness of TEL over infinite traces with the computational capacity of (incremental) Answer Set Programming (ASP). Also, we argue that finite traces are more natural when reasoning about action and change. As a result, our approach is readily implementable via multi-shot ASP systems and benefits from an extension of ASP's full-fledged input language with temporal operators. This includes future as well as past operators whose combination offers a rich temporal modeling language. For computation, we identify the class of temporal logic programs and prove that it constitutes a normal form for our approach. Finally, we outline two implementations, a generic one and an extension of the ASP system clingo. Under consideration for publication in Theory and Practice of Logic Programming (TPLP)}, language = {en} } @article{GebserObermeierOttoetal.2018, author = {Gebser, Martin and Obermeier, Philipp and Otto, Thomas and Schaub, Torsten and Sabuncu, Orkunt and Van Nguyen, and Tran Cao Son,}, title = {Experimenting with robotic intra-logistics domains}, series = {Theory and practice of logic programming}, volume = {18}, journal = {Theory and practice of logic programming}, number = {3-4}, publisher = {Cambridge Univ. Press}, address = {New York}, issn = {1471-0684}, doi = {10.1017/S1471068418000200}, pages = {502 -- 519}, year = {2018}, abstract = {We introduce the asprilo1 framework to facilitate experimental studies of approaches addressing complex dynamic applications. For this purpose, we have chosen the domain of robotic intra-logistics. This domain is not only highly relevant in the context of today's fourth industrial revolution but it moreover combines a multitude of challenging issues within a single uniform framework. This includes multi-agent planning, reasoning about action, change, resources, strategies, etc. In return, asprilo allows users to study alternative solutions as regards effectiveness and scalability. Although asprilo relies on Answer Set Programming and Python, it is readily usable by any system complying with its fact-oriented interface format. This makes it attractive for benchmarking and teaching well beyond logic programming. More precisely, asprilo consists of a versatile benchmark generator, solution checker and visualizer as well as a bunch of reference encodings featuring various ASP techniques. Importantly, the visualizer's animation capabilities are indispensable for complex scenarios like intra-logistics in order to inspect valid as well as invalid solution candidates. Also, it allows for graphically editing benchmark layouts that can be used as a basis for generating benchmark suites.}, language = {en} } @misc{SchneiderShigeyamaKovacsetal.2018, author = {Schneider, Oliver and Shigeyama, Jotaro and Kovacs, Robert and Roumen, Thijs Jan and Marwecki, Sebastian and B{\"o}ckhoff, Nico and Gl{\"o}ckner, Daniel Amadeus Johannes and Bounama, Jonas and Baudisch, Patrick}, title = {DualPanto}, series = {UIST '18: Proceedings of the 31st Annual ACM Symposium on User Interface Software and Technology}, journal = {UIST '18: Proceedings of the 31st Annual ACM Symposium on User Interface Software and Technology}, publisher = {Association for Computing Machinery}, address = {New York}, isbn = {978-1-4503-5948-1}, doi = {10.1145/3242587.3242604}, pages = {877 -- 887}, year = {2018}, abstract = {We present a new haptic device that enables blind users to continuously track the absolute position of moving objects in spatial virtual environments, as is the case in sports or shooter games. Users interact with DualPanto by operating the me handle with one hand and by holding on to the it handle with the other hand. Each handle is connected to a pantograph haptic input/output device. The key feature is that the two handles are spatially registered with respect to each other. When guiding their avatar through a virtual world using the me handle, spatial registration enables users to track moving objects by having the device guide the output hand. This allows blind players of a 1-on-1 soccer game to race for the ball or evade an opponent; it allows blind players of a shooter game to aim at an opponent and dodge shots. In our user study, blind participants reported very high enjoyment when using the device to play (6.5/7).}, language = {en} } @misc{HerzogHoenigSchroederPreikschatetal.2019, author = {Herzog, Benedict and H{\"o}nig, Timo and Schr{\"o}der-Preikschat, Wolfgang and Plauth, Max and K{\"o}hler, Sven and Polze, Andreas}, title = {Bridging the Gap}, series = {e-Energy '19: Proceedings of the Tenth ACM International Conference on Future Energy Systems}, journal = {e-Energy '19: Proceedings of the Tenth ACM International Conference on Future Energy Systems}, publisher = {Association for Computing Machinery}, address = {New York}, isbn = {978-1-4503-6671-7}, doi = {10.1145/3307772.3330176}, pages = {428 -- 430}, year = {2019}, abstract = {The recent restructuring of the electricity grid (i.e., smart grid) introduces a number of challenges for today's large-scale computing systems. To operate reliable and efficient, computing systems must adhere not only to technical limits (i.e., thermal constraints) but they must also reduce operating costs, for example, by increasing their energy efficiency. Efforts to improve the energy efficiency, however, are often hampered by inflexible software components that hardly adapt to underlying hardware characteristics. In this paper, we propose an approach to bridge the gap between inflexible software and heterogeneous hardware architectures. Our proposal introduces adaptive software components that dynamically adapt to heterogeneous processing units (i.e., accelerators) during runtime to improve the energy efficiency of computing systems.}, language = {en} }