@inproceedings {INPROC-2011-84, author = {Stamatia Rizou and Frank D{\"u}rr and Kurt Rothermel}, title = {{Fulfilling End-to-End Latency Constraints in Large-scale Streaming Environments}}, booktitle = {Proceedings of the 30th IEEE International Performance Computing and Communications Conference: IPCCC'11}, publisher = {IEEE Xplore}, institution = {University of Stuttgart : Collaborative Research Center SFB 627 (Nexus: World Models for Mobile Context-Based Systems), Germany}, pages = {1--8}, type = {Conference Paper}, month = {November}, year = {2011}, language = {English}, cr-category = {C.2.4 Distributed Systems, C.2.2 Network Protocols, C.2.3 Network Operations}, ee = {ftp://ftp.informatik.uni-stuttgart.de/pub/library/ncstrl.ustuttgart_fi/INPROC-2011-84/INPROC-2011-84.pdf}, department = {University of Stuttgart, Institute of Parallel and Distributed Systems, Distributed Systems}, abstract = {The on-line processing of high volume data streams is a prerequisite for many modern applications relying on real-time data such as global sensor networks or multimedia streaming. In order to achieve efficient data processing and scalability w.r.t. the number of distributed data sources and applications, in-network processing of data streams in an overlay network of data processing operators has been proposed. For such stream processing overlay networks, the placement of operators onto physical hosts plays an important role for the resulting quality of service—in particular, the endto- end latency—and network load. To this end, we present an enhanced placement algorithm that minimizes the network load put onto the system by a stream processing task under userdefined delay constraints in this paper. Our algorithm finds first the optimal solution in terms of network load and then degrades this solution to find a constrained optimum. In order to reduce the overhead of the placement algorithm, we included mechanisms to reduce the search space in terms of hosts that are considered during operator placement. Our evaluations show that this approach leads to an operator placement of high quality solution while inducing communication overhead proportional only to a small percentage of the total hosts.}, url = {http://www2.informatik.uni-stuttgart.de/cgi-bin/NCSTRL/NCSTRL_view.pl?id=INPROC-2011-84&engl=1} } @inproceedings {INPROC-2011-76, author = {Hannes Wolf and Klaus Herrmann and Kurt Rothermel}, title = {{FlexCon – Robust Context Handling in Human-Oriented Pervasive Flows}}, booktitle = {On the Move to Meaningful Internet Systems: OTM 2011 Confederated International Conferences: CoopIS, DOA-SVI, and ODBASE 2011, Hersonissos, Crete, Greece, October 17-21, 2011, Proceedings, Part I}, editor = {Robert Meersman and Tharam Dillon and Pilar Herrero and Akhil Kumar and Manfred Reichert and Li Qing and Beng-Chin Ooi and Ernesto Damiani and Douglas C. Schmidt and Jules White White and Manfred Hauswirth and Pascal Hitzler and Mukesh Mohania}, address = {Berlin/Heidelberg}, publisher = {Springer Berlin Heidelberg}, institution = {University of Stuttgart, Faculty of Computer Science, Electrical Engineering, and Information Technology, Germany}, series = {Lecture Notes in Computer Science}, volume = {7044}, pages = {236--255}, type = {Conference Paper}, month = {October}, year = {2011}, issn = {1611-3349}, doi = {10.1007/978-3-642-25109-2_16}, language = {English}, cr-category = {H.4.1 Office Automation, G.3 Probability and Statistics}, ee = {ftp://ftp.informatik.uni-stuttgart.de/pub/library/ncstrl.ustuttgart_fi/INPROC-2011-76/INPROC-2011-76.pdf, http://www.springerlink.com/content/2245482r612336ln/}, contact = {wolfhs@ipvs.uni-stuttgart.de}, department = {University of Stuttgart, Institute of Parallel and Distributed Systems, Distributed Systems}, abstract = {Workflows are increasingly becoming a universal means for driving and coordinating complex processes, not only in the business world but also in areas like pervasive computing. Pervasive flows run in parallel with the user{\^a}€™s real-world actions and are synchronized using automatically collected context information about her current activities (context events). Respective workflows cannot be rigidly defined since the user needs to retain her flexibility and must not be obstructed by the workflow. However, if the order of activities is not defined until the activities are actually executed, correctly assigning the uncertain context events becomes a major challenge. We propose FlexCon {\^a}€“ a novel event assignment approach for such human-oriented workflows that is based on hybrid workflow models and Dynamic Bayesian Networks. FlexCon exploits the dependency between context events to provide more accurate information as to which events need to be consumed by which workflow activities. Our evaluations show that FlexCon improves the event accuracy on average by 54\% and the number of successful completed flows on average by 88\%. Thus, FlexCon represents a major step towards unobtrusive pervasive applications.}, url = {http://www2.informatik.uni-stuttgart.de/cgi-bin/NCSTRL/NCSTRL_view.pl?id=INPROC-2011-76&engl=1} } @inproceedings {INPROC-2011-74, author = {Patrick Baier and Harald Weinschrott and Frank D{\"u}rr}, title = {{Effiziente automatisierte Erstellung von Stra{\ss}enkarten}}, booktitle = {7.GI/ITG KuVS-Fachgespr{\"a}ch. Ortsbezogene Anwendungen und Dienste.}, editor = {Roth J{\"o}rg K{\"u}pper Axel}, address = {Berlin}, publisher = {Logos Verlag Berlin GmbH}, institution = {University of Stuttgart, Faculty of Computer Science, Electrical Engineering, and Information Technology, Germany}, pages = {85--92}, type = {Conference Paper}, month = {September}, year = {2011}, isbn = {978-3-8325-2935-2}, language = {German}, cr-category = {C.2.1 Network Architecture and Design, C.2.2 Network Protocols, C.2.3 Network Operations, C.2.4 Distributed Systems, E.1 Data Structures}, ee = {ftp://ftp.informatik.uni-stuttgart.de/pub/library/ncstrl.ustuttgart_fi/INPROC-2011-74/INPROC-2011-74.pdf}, department = {University of Stuttgart, Institute of Parallel and Distributed Systems, Distributed Systems}, abstract = {Das relativ junge Paradigma des Urban Sensing erm{\"o}glicht die kosteng{\"u}nstige Bereitstellung von Sensordaten, welche in diesem Umfang bisher nicht zug{\"a}nglich waren. Ein potentieller Verwendungszweck dieser Daten liegt im Bereich der Kartografie, indem von Mobilger{\"a}ten erfasste GPS-Daten genutzt werden, um Stra{\ss}enkarten automatisch zu erstellen. Dadurch kann eine Ersparnis hinsichtlich Aufwand und Kosten, im Vergleich zu konventionellen Methoden der Kartenerstellung, erzielt werden. Diese Arbeit stellt einen solchen Ansatz zur effizienten, automatisierten Erstellung von Stra{\ss}enkarten mithilfe von GPS-Sensordaten vor. Diese Daten werden dabei automatisch von Personen gesammelt, die ihre Mobilger{\"a}te wie gewohnt mit sich f{\"u}hren, zus{\"a}tzlich aber auf ihren allt{\"a}glichen Wegen GPS-Positionsinformationen erfassen, welche sie einem zentralen System zur Verf{\"u}gung stellen. Dies geschieht automatisch, ohne dass eine Interaktion dieser Personen n{\"o}tig ist. Im Gegenzug soll der Ressourcenverbrauch der teilnehmenden Mobilger{\"a}te m{\"o}glichst minimiert werden. Daher koordiniert der in dieser Arbeit vorgestellte Ansatz die Erfassung der GPS-Daten so, dass die Mobilger{\"a}te diese m{\"o}glichst nur dann erfassen, wenn sie sich in einem Gebiet befinden, welches bis zu diesem Zeitpunkt noch nicht ausreichend kartografisch erfasst wurde. Um diese gezielte Koordination der Mobilger{\"a}te zu erm{\"o}glichen, werden im Rahmen dieser Arbeit Qualit{\"a}tsmetriken f{\"u}r Geodaten vorgestellt, welche den erfassten Stra{\ss}en quantitative Gr{\"o}{\ss}en zuordnen, um so einen Vergleich dieser Daten zu erm{\"o}glichen.}, url = {http://www2.informatik.uni-stuttgart.de/cgi-bin/NCSTRL/NCSTRL_view.pl?id=INPROC-2011-74&engl=1} } @inproceedings {INPROC-2011-73, author = {Damian Philipp and Frank D{\"u}rr and Kurt Rothermel}, title = {{A Sensor Network Abstraction for Flexible Public Sensing Systems}}, booktitle = {Proceedings of the 8th IEEE International Conference on Mobile Ad-Hoc and Sensor Systems: MASS'11; Valencia, Spain, October 17-22, 2011}, editor = {IEEE Computer Society Conference Publishing Services}, address = {Valencia}, publisher = {IEEE Computer Society Conference Publishing Services}, institution = {University of Stuttgart, Faculty of Computer Science, Electrical Engineering, and Information Technology, Germany}, series = {IEEE Computer Society Order Number}, volume = {E4469}, pages = {460--469}, type = {Conference Paper}, month = {October}, year = {2011}, doi = {10.1109/MASS.2011.52}, isbn = {978-0-7695-4469-4/11}, keywords = {Public Sensing; Sensor Networks; Smartphone}, language = {English}, cr-category = {C.2.1 Network Architecture and Design, C.2.4 Distributed Systems, C.2.5 Local and Wide-Area Networks, C.5.3 Microcomputers}, ee = {ftp://ftp.informatik.uni-stuttgart.de/pub/library/ncstrl.ustuttgart_fi/INPROC-2011-73/INPROC-2011-73.pdf, http://dx.doi.org/10.1109/MASS.2011.52, http://www.comnsense.de}, contact = {damian.philipp@ipvs.uni-stuttgart.de, frank.duerr@ipvs.uni-stuttgart.de, kurt.rothermel@ipvs.uni-stuttgart.de}, department = {University of Stuttgart, Institute of Parallel and Distributed Systems, Distributed Systems}, abstract = {Public Sensing is a new paradigm for developing large-scale sensor networks at low cost by utilizing mobile phones that are already surrounding us in our everyday lives. In this paper we present a sensor network abstraction layer for creating flexible public sensing systems that can execute arbitrary queries. To this effect we develop several algorithms to select mobile nodes for executing a query. These algorithms allow a user to define a trade-off between quality and efficiency of query execution by choosing an appropriate algorithm. Our evaluations show that we can achieve a 99$\backslash$\% increase in efficiency with the most efficient approaches and only about 10$\backslash$\% decrease in result quality under worst conditions.}, url = {http://www2.informatik.uni-stuttgart.de/cgi-bin/NCSTRL/NCSTRL_view.pl?id=INPROC-2011-73&engl=1} } @inproceedings {INPROC-2011-70, author = {Hannes Wolf and Jonas Palauro and Klaus Herrmann}, title = {{Fuzzy Event Assignment for Robust Context-Aware Workflows}}, booktitle = {Proceedings of The Fourth International Conference on Dependability (DEPEND 2011)}, editor = {IARIA}, address = {Nice/Saint Laurent du Var, France}, publisher = {IARIA}, institution = {University of Stuttgart, Faculty of Computer Science, Electrical Engineering, and Information Technology, Germany}, pages = {37--42}, type = {Conference Paper}, month = {August}, year = {2011}, isbn = {978-1-61208-149-6}, keywords = {context-aware workflows, dependable event assignment, fuzzy logic}, language = {English}, cr-category = {H.4.1 Office Automation, I.2.3 Deduction and Theorem Proving}, ee = {ftp://ftp.informatik.uni-stuttgart.de/pub/library/ncstrl.ustuttgart_fi/INPROC-2011-70/INPROC-2011-70.pdf}, department = {University of Stuttgart, Institute of Parallel and Distributed Systems, Distributed Systems}, abstract = {The dependability of any kind of context-aware pervasive system inherently relies on the ability to detect and recognize context events robustly. However, due to the inaccuracy of real-world sensors the accurate recognition and handling of context information is a fundamental problem leading to ambiguities and inconsistent behavior of applications. Adaptable Pervasive Flows (APF) are a novel workflow-based programming paradigm for pervasive applications. An APF encodes the temporal dependencies of a user’s tasks. We propose a Fuzzy Event Assignment (FEvA) algorithm that exploits this flow-knowledge to significantly improve the robustness of context-aware pervasive applications by resolving the ambiguities inherent to the context data. Our experiments show that FEvA reaches an event assignment accuracy of 78\% to 97\% and improves the performance of dealing with false positive, out-of-order events, and missed context information.}, url = {http://www2.informatik.uni-stuttgart.de/cgi-bin/NCSTRL/NCSTRL_view.pl?id=INPROC-2011-70&engl=1} } @inproceedings {INPROC-2011-61, author = {Lars Geiger and Frank D{\"u}rr and Kurt Rothermel}, title = {{Adaptive Routing in a Contextcast Overlay Network}}, booktitle = {Proceedings of the IEEE 7th International Conference on Wireless and Mobile Computing, Networking and Communications (WiMob 2011)}, publisher = {IEEE Xplore}, institution = {University of Stuttgart : Collaborative Research Center SFB 627 (Nexus: World Models for Mobile Context-Based Systems), Germany}, pages = {1--8}, type = {Conference Paper}, month = {October}, year = {2011}, doi = {10.1109/WiMOB.2011.6085340}, language = {English}, cr-category = {C.2.1 Network Architecture and Design, C.2.2 Network Protocols, C.2.4 Distributed Systems, C.2.6 Internetworking}, ee = {ftp://ftp.informatik.uni-stuttgart.de/pub/library/ncstrl.ustuttgart_fi/INPROC-2011-61/INPROC-2011-61.pdf, http://dx.doi.org/10.1109/WiMOB.2011.6085340}, department = {University of Stuttgart, Institute of Parallel and Distributed Systems, Distributed Systems}, abstract = {Context-based communication allows for the dissemination of messages to mobile users with a specified context, i.e., at a location and with certain attribute values. This enables, e.g., a message to students on campus attending a certain class, with information about a study group for an upcoming exam. An overlay network of context-aware routers efficiently disseminate the messages to all matching receivers. Directed forwarding of such messages requires that the routers maintain knowledge about the contexts of connected users. Global knowledge, i.e., each router knowing about every user, scales poorly, though, because of the necessary updates. To overcome this challenge, a router can selectively propagate context information that actually allows its neighbors to prune a message distribution tree. In this paper, we present an approach to adaptively propagate only those user contexts that offer a reduction in overall system load. The algorithm automatically and locally adapts to the observed messages and user contexts on each node. Our solution significantly improves the scalability of the system by reducing the overall load by almost 50\%.}, url = {http://www2.informatik.uni-stuttgart.de/cgi-bin/NCSTRL/NCSTRL_view.pl?id=INPROC-2011-61&engl=1} } @inproceedings {INPROC-2011-59, author = {Bilal Hameed and Jorge Minguez and Michael W{\"o}rner and Philip Hollstein and Sema Zor and Stefan Silcher and Frank D{\"u}rr and Kurt Rothermel}, title = {{The Smart Real-Time Factory as a Product Service System}}, booktitle = {3rd CIRP International Conference on Industrial Product Service Systems}, address = {Braunschweig, Germany}, publisher = {IRP}, institution = {University of Stuttgart, Faculty of Computer Science, Electrical Engineering, and Information Technology, Germany}, pages = {1--6}, type = {Conference Paper}, month = {January}, year = {2011}, language = {English}, cr-category = {C.2.4 Distributed Systems}, department = {University of Stuttgart, Institute of Parallel and Distributed Systems, Distributed Systems}, abstract = {In modern manufacturing landscape, companies are increasingly relying on product service systems i.e. bundling of products and services together in order to gain a competitive edge. In this article we present the Smart Real-Time Factory, a smart digital manufacturing environment that can transform the process of production into an informational service for the customers. The different components of the smart factory are discussed at length along with a discussion of the different services that can be offered by the smart factory.}, url = {http://www2.informatik.uni-stuttgart.de/cgi-bin/NCSTRL/NCSTRL_view.pl?id=INPROC-2011-59&engl=1} } @inproceedings {INPROC-2011-51, author = {Patrick Baier and Harald Weinschrott and Frank D{\"u}rr and Kurt Rothermel}, title = {{MapCorrect: Automatic Correction and Validation of Road Maps Using Public Sensing}}, booktitle = {36th Annual IEEE Conference on Local Computer Networks (LCN 2011)}, address = {Bonn, Germany}, publisher = {IEEE Computer Society}, institution = {University of Stuttgart, Faculty of Computer Science, Electrical Engineering, and Information Technology, Germany}, pages = {1--8}, type = {Conference Paper}, month = {October}, year = {2011}, keywords = {ad-hoc; mobile; public sensing}, language = {English}, cr-category = {C.2 Computer-Communication Networks}, ee = {ftp://ftp.informatik.uni-stuttgart.de/pub/library/ncstrl.ustuttgart_fi/INPROC-2011-51/INPROC-2011-51.pdf, http://www.comnsense.de}, contact = {patrick.baier@ipvs.uni-stuttgart.de}, department = {University of Stuttgart, Institute of Parallel and Distributed Systems, Distributed Systems}, abstract = {With the increasing proliferation of small and cheap GPS receivers, a new way of generating road maps could be witnessed over the last few years. Participatory mapping approaches like OpenStreetMap, for instance, introduced a way to generate road maps collaboratively from scratch. Nevertheless, one of the main problems of these maps is their unknown quality in terms of accuracy. To address this issue, we propose MapCorrect: An automatic map correction and validation system. MapCorrect automatically collects GPS traces from people's mobile devices to correct a given road map and validate it. Since the collection of GPS data raises concerns about the energy consumption of the participating mobile devices, we tackle this issue by introducing a selective sensing mechanism. Furthermore, we show by simulation that using this approach up to 50\% of energy on the mobile phones can be saved while not impairing the map correction and validation process at all.}, url = {http://www2.informatik.uni-stuttgart.de/cgi-bin/NCSTRL/NCSTRL_view.pl?id=INPROC-2011-51&engl=1} } @inproceedings {INPROC-2011-49, author = {Stefan F{\"o}ll and Klaus Herrmann and Kurt Rothermel}, title = {{PreCon - Expressive Context Prediction using Stochastic Model Checking}}, booktitle = {Proceedings of the 8th International Conference on Ubiquitous Intelligence and Computing (UIC 2011)}, address = {Banff, Canada}, publisher = {Springer-Verlag}, institution = {University of Stuttgart, Faculty of Computer Science, Electrical Engineering, and Information Technology, Germany}, series = {Lecture Notes in Computer Science}, pages = {1--15}, type = {Conference Paper}, month = {September}, year = {2011}, keywords = {Context Prediction, Semi-Markov Model, Stochastic Model Checking, Temporal Logic}, language = {German}, cr-category = {G.3 Probability and Statistics, I.2.6 Artificial Intelligence Learning, I.6.4 Model Validation and Analysis}, ee = {ftp://ftp.informatik.uni-stuttgart.de/pub/library/ncstrl.ustuttgart_fi/INPROC-2011-49/INPROC-2011-49.pdf, http://www.springerlink.com/content/xv8821301mh22473/}, contact = {stefan.foell@ipvs.uni-stuttgart.de}, department = {University of Stuttgart, Institute of Parallel and Distributed Systems, Distributed Systems}, abstract = {Ubiquitous systems need to determine the context of humans to deliver the right services at the right time. As the needs of humans are often coupled to their future context, the ability to predict relevant changes in a user's context is a key factor for providing intelligence and proactivity. Current context prediction systems only allow applications to query for the next user context (e.g. the user's next location). This severely limits the benefit of context prediction since these approaches cannot answer more expressive time-dependent queries (e.g. will the user enter location X within the next 10 minutes?). Neither can they handle predictions of multi-dimensional context (e.g. activity and location). We propose PreCon, a new approach to predicting multi-dimensional context. PreCon improves query expressiveness, providing clear formal semantics by applying stochastic model checking methods. PreCon is composed of three major parts: a stochastic model to represent context changes, an expressive temporal-logic query language, and stochastic algorithms for predicting context. In our evaluations, we apply PreCon to real context traces from the domain of healthcare and analyse the performance using well-known metrics from information retrieval. We show that PreCon reaches an F-score (combined precision and recall) of about 0.9 which indicates a very good performance.}, url = {http://www2.informatik.uni-stuttgart.de/cgi-bin/NCSTRL/NCSTRL_view.pl?id=INPROC-2011-49&engl=1} } @inproceedings {INPROC-2011-44, author = {Marco V{\"o}lz and Boris Koldehofe and Kurt Rothermel}, title = {{Supporting Strong Reliability for Distributed Complex Event Processing Systems}}, booktitle = {Proceedings of 13th IEEE International Conference on High Performance Computing and Communications (HPCC-2011)}, publisher = {IEEE Computer Society Press}, institution = {University of Stuttgart, Faculty of Computer Science, Electrical Engineering, and Information Technology, Germany}, pages = {477--486}, type = {Conference Paper}, month = {September}, year = {2011}, doi = {10.1109/HPCC.2011.69}, language = {English}, cr-category = {C.2.4 Distributed Systems}, ee = {ftp://ftp.informatik.uni-stuttgart.de/pub/library/ncstrl.ustuttgart_fi/INPROC-2011-44/INPROC-2011-44.pdf}, department = {University of Stuttgart, Institute of Parallel and Distributed Systems, Distributed Systems}, abstract = {Many application classes such as monitoring applications, involve processing a massive amount of data from a possibly huge number of data sources. Complex Event Processing (CEP) has evolved as the paradigm of choice to determine meaningful situations (complex events) by performing stepwise correlation over event streams. To keep up with the high scalability demands of growing input streams, recent approaches distribute event correlation over several correlation nodes. However, the distribution of event correlation severely limits the reliability of a CEP system. Already a failure of a single correlation node impacts the correctness of the final correlation result. Increasing the availability by a naive application of established replication principles introduces new problems in the context of CEP. In particular, ensuring the lossless delivery of events and the detection of duplicate events before processing them is a challenging task. In this paper, we illustrate the importance of a strong reliability semantics for CEP in the context of a monitoring application in a distributed production environment. Strong reliability ensures each complex event is detected and delivered exactly once to each application entity. We present a replication scheme which ensures strong reliability in an asynchronous system model and can be applied to an arbitrary distributed CEP system. The algorithm tolerates f simultaneous failures by introducing f additional replicas for each correlation node. We prove correctness as well as evaluate the overhead introduced by the algorithm. Results show, that the overhead scales linearly with the number of deployed replicas and the node failure rate.}, url = {http://www2.informatik.uni-stuttgart.de/cgi-bin/NCSTRL/NCSTRL_view.pl?id=INPROC-2011-44&engl=1} } @inproceedings {INPROC-2011-43, author = {Bj{\"o}rn Schilling and Boris Koldehofe and Kurt Rothermel}, title = {{Efficient and Distributed Rule Placement in Heavy Constraint-Driven Event Systems}}, booktitle = {Proceedings of the 13th IEEE International Conference on High Performance Computing and Communications (HPCC-2011)}, publisher = {IEEE}, institution = {University of Stuttgart, Faculty of Computer Science, Electrical Engineering, and Information Technology, Germany}, pages = {355--364}, type = {Conference Paper}, month = {September}, year = {2011}, doi = {10.1109/HPCC.2011.53}, language = {English}, cr-category = {C.2.4 Distributed Systems}, ee = {ftp://ftp.informatik.uni-stuttgart.de/pub/library/ncstrl.ustuttgart_fi/INPROC-2011-43/INPROC-2011-43.pdf, http://dx.doi.org/10.1109/HPCC.2011.53}, department = {University of Stuttgart, Institute of Parallel and Distributed Systems, Distributed Systems}, abstract = {Complex Event Processing (CEP) is of increasing importance in many industrial applications to integrate a huge number of events in a scalable manner. A core challenge towards scalable CEP is to efficiently distribute the rules which define how correlations between events can be detected within an event processing network. Furthermore, migration of rules is essential to adapt to changing conditions. While recently significant effort has been spent on optimizing CEP with respect to dedicated optimization goals, such as minimizing latency and bandwidth usage, there remains a fundamental gap in supporting requirements that emerge from deploying CEP over heterogeneous and independent processing environments. Heterogeneity typically imposes many constraints on the placement of rules, which increases the complexity of the underlying optimization problem and cannot be handled efficiently by existing solutions. In this paper we examine the distributed placement, migration and optimization of rules in the context of the constraint optimization problem to minimize network usage. We propose and evaluate a placement algorithm that efficiently finds valid solutions in scenarios where the solution space is heavily restricted by constraints. The algorithm operates in a decentralized way and is adaptive to dynamic changes of processing nodes, rules, and load characteristics of the event processing network. The optimization algorithm adopts techniques from simulated annealing to avoid local minima. Furthermore, the proposed rule migration policies resolve invalid placements quickly and therefore ensure high availability. The evaluations show that the proposed algorithm is able to efficiently find near optimum solutions within heavy constraint-driven network conditions.}, url = {http://www2.informatik.uni-stuttgart.de/cgi-bin/NCSTRL/NCSTRL_view.pl?id=INPROC-2011-43&engl=1} } @inproceedings {INPROC-2011-31, author = {Daniel Fischer and Stefan F{\"o}ll and Klaus Herrmann and Kurt Rothermel}, title = {{Energy-efficient Workflow Distribution}}, booktitle = {Proceedings of the Fifth International Conference on Communication System Software and Middleware(COMSWARE 2011)}, address = {Verona, Italy}, publisher = {ACM}, institution = {University of Stuttgart, Faculty of Computer Science, Electrical Engineering, and Information Technology, Germany}, pages = {1--8}, type = {Conference Paper}, month = {July}, year = {2011}, keywords = {Workflow distribution; Energy efficiency; Minimum Cut}, language = {English}, cr-category = {C.2.4 Distributed Systems, H.4 Information Systems Applications}, ee = {ftp://ftp.informatik.uni-stuttgart.de/pub/library/ncstrl.ustuttgart_fi/INPROC-2011-31/INPROC-2011-31.pdf, http://doi.acm.org/10.1145/2016551.2016553}, department = {University of Stuttgart, Institute of Parallel and Distributed Systems, Distributed Systems}, abstract = {Pervasive computing and business process modeling are joining forces, as mobile human users shall be seamlessly integrated into business processes. This current trend gains momentum. In respective scenarios, humans use mobile devices and wireless communication technology to interact with electronic workflows that are entirely running in some powerful back-end infrastructure. However, the high degree of interaction between humans and their workflows causes a high communication overhead, which consumes a significant amount of energy on the mobile devices. This incurs a negative impact on the usability and on the efficiency of the overall business process due to rapidly drained batteries and the resulting short life-times of the devices and applications. We present an approach based on the well-known minimum-cut algorithm for reducing the costly data transmissions during workflow execution by distributing parts of a workflow to the users' devices. Our main motivation is to reduce the energy consumption on the mobile devices and, thus, avoid situations in which batteries are drained in the field, rendering the usage of mobile devices more efficient. We prove that our algorithm finds the optimal solution for a given network and a workflow. Our evaluations show that our approach decreases the energy consumed on mobile devices by 32-37\% compared to an approach where the entire workflow is executed in a central infrastructure. Thus, if mobile devices are primarily used for executing workflows (as seen in application domains like logistics and health care), one third of the energy can be saved. This either means that devices have to be charged less frequently, leading to less distraction in the business process, or that mobile device specifications can be lowered. Significant cost reductions result in both cases.}, url = {http://www2.informatik.uni-stuttgart.de/cgi-bin/NCSTRL/NCSTRL_view.pl?id=INPROC-2011-31&engl=1} } @inproceedings {INPROC-2011-30, author = {Andreas Benzing and Boris Koldehofe and Kurt Rothermel}, title = {{Efficient Support for Multi-Resolution Queries in Global Sensor Networks}}, booktitle = {Proceedings of the Fifth International Conference on COMmunication System softWAre and middlewaRE: COMSWARE 2011}, publisher = {ACM}, institution = {University of Stuttgart, Faculty of Computer Science, Electrical Engineering, and Information Technology, Germany}, pages = {1--12}, type = {Conference Paper}, month = {July}, year = {2011}, doi = {10.1145/2016551.2016562}, keywords = {DSPS, global sensor network, indexing, query processing}, language = {English}, cr-category = {C.2.4 Distributed Systems}, ee = {ftp://ftp.informatik.uni-stuttgart.de/pub/library/ncstrl.ustuttgart_fi/INPROC-2011-30/INPROC-2011-30.pdf, http://dl.acm.org/authorize?6553117}, contact = {andreas.benzing@ipvs.uni-stuttgart.de}, department = {University of Stuttgart, Institute of Parallel and Distributed Systems, Distributed Systems}, abstract = {Stream processing has evolved as a paradigm for efficiently sharing and integrating a massive amount of data into applications. However, the integration of globally dispersed sensor data imposes challenges in the effective utilization of the IT infrastructure that forms the global sensor network. Especially, simulations require the integration of sensor streams at widely differing spatial and temporal resolutions. For current stream processing solutions it is necessary to generate a separate data stream for each requested resolution. Therefore, these systems will suffer from high redundancy in data streams, wasting a significant amount of bandwidth and limiting their scalability. This paper presents a new approach to scalable distributed stream processing of data which stems from globally dispersed sensor networks. The approach supports applications in establishing continuous queries for sensor data at different resolutions and ensures efficient bandwidth usage of the data distribution network. Unlike existing work in the context of video stream processing which provides multiple resolutions by establishing separate channels for each resolution, this paper presents a stream processing system that can efficiently split/combine data streams in order to decrease/increase their resolution without loss in data precision. In addition the system provides mechanisms for load balancing of sensor data streams that allow efficient utilization of the bandwidth of the global sensor network.}, url = {http://www2.informatik.uni-stuttgart.de/cgi-bin/NCSTRL/NCSTRL_view.pl?id=INPROC-2011-30&engl=1} } @inproceedings {INPROC-2011-22, author = {Andreas Grau and Klaus Herrmann and Kurt Rothermel}, title = {{NETbalance: Reducing the Runtime of Network Emulation using Live Migration}}, booktitle = {Proceedings of the 20th International Conference on Computer Communication Networks (ICCCN'11)}, address = {Maui, HI, USA}, publisher = {IEEE Computer Society}, institution = {University of Stuttgart, Faculty of Computer Science, Electrical Engineering, and Information Technology, Germany}, pages = {1--6}, type = {Conference Paper}, month = {August}, year = {2011}, language = {English}, cr-category = {C.2.4 Distributed Systems}, ee = {ftp://ftp.informatik.uni-stuttgart.de/pub/library/ncstrl.ustuttgart_fi/INPROC-2011-22/INPROC-2011-22.pdf, http://dx.doi.org/10.1109/ICCCN.2011.6005793}, department = {University of Stuttgart, Institute of Parallel and Distributed Systems, Distributed Systems}, abstract = {Network emulation is an efficient method for evaluating distributed applications and communication protocols by combining the benefits of real world experiments and network simulation. The process of network emulation involves the execution of connected instances of the software under test (called virtual nodes) in a controlled environment. In previous work, we introduced an approach to minimize the runtime of network emulation experiments based on prior known average resource requirements of virtual nodes. In this paper, we introduce NETbalance, a novel approach to runtime reduction for experiments with unknown or varying resource requirements. NETbalance migrates virtual nodes during an experiment to distribute the load evenly across the physical nodes, avoiding overloaded nodes and exploiting the idle resources on underloaded nodes for speeding up the experiment execution. We make the following contributions: First, we present an emulation architecture for efficiently supporting live migration of virtual nodes. Second, we propose a cost model for determining the runtime reduction achieved through the migration. Third, we introduce an algorithm for calculating placements that minimize the experiment runtime. Our evaluations of the NETbalance prototype show, that it is able to reduce the experiment runtime by up to 70\%.}, url = {http://www2.informatik.uni-stuttgart.de/cgi-bin/NCSTRL/NCSTRL_view.pl?id=INPROC-2011-22&engl=1} } @inproceedings {INPROC-2011-19, author = {Christian Hiesinger and Daniel Fischer and Stefan F{\"o}ll and Herrmann Klaus and Kurt Rothermel}, title = {{Minimizing Human Interaction Time in Workflows}}, booktitle = {Proceedings of the Sixth International Conference on Internet and Web Applications and Services (ICIW 2011)}, address = {St. Maarten, the Netherlands Antilles}, publisher = {IARIA}, institution = {University of Stuttgart, Faculty of Computer Science, Electrical Engineering, and Information Technology, Germany}, pages = {22--28}, type = {Conference Paper}, month = {March}, year = {2011}, keywords = {Workflow distribution; human interaction; pervasive workflows}, language = {English}, cr-category = {D.2.4 Software Engineering Software/Program Verification, H.4 Information Systems Applications}, contact = {christian.hiesinger@ipvs.uni-stuttgart.de}, department = {University of Stuttgart, Institute of Parallel and Distributed Systems, Distributed Systems}, abstract = {Many business scenarios require humans to interact with workflows. To support humans as unobtrusively as possible in the execution of their activities, it is important to keep the interaction time experienced by humans as low as possible. The time required for such interactions is influenced by two factors: First, by the runtime of the services that are used by a workflow during an interaction. Second, by the time required to transfer data between workflow servers and services that may be distributed in a global network. We propose an algorithm that computes a suitable distribution of a workflow in such a network. The goal of our algorithm is to minimize the time required for interactions between a human and a workflow. Current approaches in the domain of workflow optimization pay little attention towards optimizing a workflow to increase the usability for humans. We show the feasibility of our approach by comparing our algorithm with two non-distributed approaches and a distributed approach which is based on a greedy algorithm and show that our algorithm outperforms these approaches.}, url = {http://www2.informatik.uni-stuttgart.de/cgi-bin/NCSTRL/NCSTRL_view.pl?id=INPROC-2011-19&engl=1} } @inproceedings {INPROC-2011-11, author = {Frank D{\"u}rr and Pavel Skvortsov and Kurt Rothermel}, title = {{Position Sharing for Location Privacy in Non-trusted Systems}}, booktitle = {Proceedings of the 9th IEEE International Conference on Pervasive Computing and Communications (PerCom 2011)}, address = {Seattle, USA}, publisher = {IEEE Computer Society}, institution = {University of Stuttgart, Faculty of Computer Science, Electrical Engineering, and Information Technology, Germany}, pages = {189--196}, type = {Conference Paper}, month = {March}, year = {2011}, doi = {10.1109/PERCOM.2011.5767584}, keywords = {location-based service; privacy; obfuscation; sharing; location management}, language = {English}, cr-category = {C.2.4 Distributed Systems, H.3.5 Online Information Services}, ee = {ftp://ftp.informatik.uni-stuttgart.de/pub/library/ncstrl.ustuttgart_fi/INPROC-2011-11/INPROC-2011-11.pdf, http://dx.doi.org/10.1109/PERCOM.2011.5767584, http://www.priloc.de}, department = {University of Stuttgart, Institute of Parallel and Distributed Systems, Distributed Systems}, abstract = {Many novel location-based services (LBS) such as a friend finder service require knowledge about the positions of mobile users. Usually, location services are used to manage these positions, and for providing basic functionality like spatial range queries or spatial events to the LBS. Managing and using the positions of mobile users raises privacy issues, in particular, if the providers of LBS and location services are only partially trusted. Many different approaches for preserving a user's privacy have been proposed in the literature, e.g. location obfuscation and the k-anonymity concept. However, most of them are not suitable if both LBS and location service providers are non-trusted. In contrast to these approaches, we present a novel approach for the secure management of private position information in partially trusted system environments. The main contribution in this paper is a position sharing concept which allows for the distribution of position information (shares) of strictly limited accuracy onto several location servers of different providers. With this approach, a compromised server will only reveal information of limited accuracy. Moreover, we will show how position shares of coarse granularity from multiple location servers can be fused into information of higher precision to satisfy the accuracy requirements of different LBS.}, url = {http://www2.informatik.uni-stuttgart.de/cgi-bin/NCSTRL/NCSTRL_view.pl?id=INPROC-2011-11&engl=1} } @inproceedings {INPROC-2011-10, author = {Harald Weinschrott and Julian Weisser and Frank D{\"u}rr and Kurt Rothermel}, title = {{Participatory Sensing Algorithms for Mobile Object Discovery in Urban Areas}}, booktitle = {Proceedings of the 9th Annual IEEE International Conference on Pervasive Computing and Communications}, publisher = {IEEE Computer Society}, institution = {University of Stuttgart : Collaborative Research Center SFB 627 (Nexus: World Models for Mobile Context-Based Systems), Germany}, pages = {128--135}, type = {Conference Paper}, month = {March}, year = {2011}, doi = {10.1109/PERCOM.2011.5767577}, language = {English}, cr-category = {C.2 Computer-Communication Networks}, ee = {ftp://ftp.informatik.uni-stuttgart.de/pub/library/ncstrl.ustuttgart_fi/INPROC-2011-10/INPROC-2011-10.pdf, http://dx.doi.org/10.1109/PERCOM.2011.5767577, http://www.comnsense.de}, department = {University of Stuttgart, Institute of Parallel and Distributed Systems, Distributed Systems}, abstract = {This paper introduces mechanisms for the automated detection of mobile objects in urban areas. Widely available devices such as mobile phones with integrated proximity sensors such as RFID readers or Bluetooth cooperatively perform sensing operations to discover mobile objects. In this paper, we propose a coverage metric for assessing the completeness of sensing that considers spatial and temporal aspects. To maximize coverage while minimizing energy consumption of mobile nodes, we propose both a centralized and a distributed coordination algorithm for selecting nodes that need to sense. Moreover, we present strategies that allow selected nodes to perform efficient sense operations. By extensive simulations, we show that distributed coordination achieves drastic energy savings of up to 63\%, while limiting the coverage loss to 13\%. Moreover, we show that the centralized algorithm loses less than 1\% coverage compared to the maximum possible coverage.}, url = {http://www2.informatik.uni-stuttgart.de/cgi-bin/NCSTRL/NCSTRL_view.pl?id=INPROC-2011-10&engl=1} } @inproceedings {INPROC-2011-09, author = {Umakishore Ramachandran and Liviu Iftode and Rajnish Kumar and Santosh Pande and Kurt Rothermel and Boris Koldehofe}, title = {{Large-scale Situational Awareness with Camera Networks and Multimodal Sensing}}, booktitle = {NSF Workshop on Pervasive Computing at Scale (PeCS)}, publisher = {online}, institution = {University of Stuttgart, Faculty of Computer Science, Electrical Engineering, and Information Technology, Germany}, pages = {1--2}, type = {Workshop Paper}, month = {January}, year = {2011}, keywords = {Distributed Systems}, language = {English}, cr-category = {C.2.4 Distributed Systems}, department = {University of Stuttgart, Institute of Parallel and Distributed Systems, Distributed Systems}, abstract = {This white paper raises the challenges and solution approaches for dealing with large-scale media-rich infrastructures for addressing the needs of large-scale sensor-based applications, often classified as situation awareness applications, using smart surveillance as a canonical example.}, url = {http://www2.informatik.uni-stuttgart.de/cgi-bin/NCSTRL/NCSTRL_view.pl?id=INPROC-2011-09&engl=1} } @inproceedings {INPROC-2011-08, author = {Gerald G. Koch and Andreas Benzing and Christoph P. Mayer}, title = {{An Approach for Urban Sensing with Quality-Aware Situation Detection and Efficient Communication}}, booktitle = {Proceedings of the Workshops der wissenschaftlichen Konferenz Kommunikation in verteilten Systemen 2011 (WowKiVS 2011); Kiel, Germany, March 11th, 2011}, editor = {Horst Hellbr{\"u}ck and Norbert Luttenberger and Volker Turau}, publisher = {EASST}, institution = {University of Stuttgart, Faculty of Computer Science, Electrical Engineering, and Information Technology, Germany}, series = {Electronic Communications of the EASST}, pages = {1--10}, type = {Workshop Paper}, month = {March}, year = {2011}, issn = {1863-2122}, keywords = {Urban sensing; Internet of Things; Complex Event Processing; CEP; Delay Tolerant Network; DTN; Distributed Diagnostic Simulation}, language = {English}, cr-category = {C.2.2 Network Protocols, C.2.4 Distributed Systems, I.6.3 Simulation and Modeling Applications}, ee = {ftp://ftp.informatik.uni-stuttgart.de/pub/library/ncstrl.ustuttgart_fi/INPROC-2011-08/INPROC-2011-08.pdf}, contact = {gerald.koch@ipvs.uni-stuttgart.de andreas.benzing@ipvs.uni-stuttgart.de mayer@kit.edu}, department = {University of Stuttgart, Institute of Parallel and Distributed Systems, Distributed Systems}, abstract = {Urban Sensing employs physical-world mining to create a digital model of the physical world using a large number of sensors. Handling the large amount of data generated by sensors is costly and requires energy-saving measures for sensing and sensor data transmission. Such schemes often affect data quality and message delay. However, the detection of real-world situations using Complex Event Processing on sensor data has to be dependable and timely and requires precise data. In this position paper, we propose an approach to integrate the contradicting optimization goals of energy-efficient wireless sensor networks and dependable situation detection. It separates the system into the following tiers: First, to support energy-efficiency and allow sparse, unconnected sensor networks, we exploit the mobility of people through Delay Tolerant Networking for collecting sensor data. This frees sensor nodes from energy-expensive routing. Second, we employ Diagnostic Simulation which provides data that is complete, precise and in time and therefore supports quality-aware situation detection.}, url = {http://www2.informatik.uni-stuttgart.de/cgi-bin/NCSTRL/NCSTRL_view.pl?id=INPROC-2011-08&engl=1} } @article {ART-2011-21, author = {Tobias Farrell and Kurt Rothermel and Reynold Cheng}, title = {{Processing Continuous Range Queries with Spatiotemporal Tolerance}}, journal = {IEEE Journal Transactions on Mobile Computing (TCM)}, publisher = {IEEE Computer Society}, volume = {10}, number = {3}, pages = {320--334}, type = {Article in Journal}, month = {March}, year = {2011}, doi = {10.1109/TMC.2010.159}, issn = {1536-1233}, keywords = {accuracy; delay; energy consumption; sensors; uncertainty; query; spatial; temporal; spatiotemporal}, language = {English}, cr-category = {C.2 Computer-Communication Networks}, department = {University of Stuttgart, Institute of Parallel and Distributed Systems, Distributed Systems}, abstract = {Continuous queries are often employed to monitor the locations of mobile objects (MOs), which are determined by sensing devices like GPS receivers. In this paper, we tackle two challenges in processing continuous range queries (CRQs): coping with data uncertainty inherently associated with location data, and reducing the energy consumption of battery-powered MOs. We propose the concept of spatiotemporal tolerance for CRQ to relax a query's accuracy requirements in terms of a maximal acceptable error. Unlike previous works, our definition considers tolerance in both the spatial and temporal dimensions, which offers applications more flexibility in specifying their individual accuracy requirements. As we will show, these tolerance bounds can provide well-defined query semantics in spite of different sources of data uncertainty. In addition, we present efficient algorithms that carefully control when an MO should sense or report a location, while satisfying these tolerances. Thereby, we particularly reduce the number of position sensing operations substantially, which constitute a considerable source of energy consumption. Extensive simulations confirm that the proposed algorithms result in large energy savings compared to nontolerant query processing.}, url = {http://www2.informatik.uni-stuttgart.de/cgi-bin/NCSTRL/NCSTRL_view.pl?id=ART-2011-21&engl=1} } @article {ART-2011-11, author = {Ralph Lange and Frank D{\"u}rr and Kurt Rothermel}, title = {{Efficient real-time trajectory tracking}}, journal = {The VLDB Journal}, publisher = {Springer Berlin Heidelberg}, volume = {20}, number = {5}, pages = {671--694}, type = {Article in Journal}, month = {October}, year = {2011}, doi = {10.1007/s00778-011-0237-7}, issn = {1066-8888}, keywords = {moving objects database; MOD; trajectory tracking; dead reckoning; line simplification}, language = {English}, cr-category = {H.2.8 Database Applications}, ee = {ftp://ftp.informatik.uni-stuttgart.de/pub/library/ncstrl.ustuttgart_fi/ART-2011-11/ART-2011-11.pdf, http://dx.doi.org/10.1007/s00778-011-0237-7}, contact = {ralph.lange@ipvs.uni-stuttgart.de}, department = {University of Stuttgart, Institute of Parallel and Distributed Systems, Distributed Systems}, abstract = {Moving objects databases (MOD) manage trajectory information of vehicles, animals, and other mobile objects. A crucial problem is how to efficiently track an object's trajectory in real-time, in particular if the trajectory data is sensed at the mobile object and thus has to be communicated over a wireless network. We propose a family of tracking protocols that allow trading the communication cost and the amount of trajectory data stored at a MOD off against the spatial accuracy. With each of these protocols, the MOD manages a simplified trajectory that does not deviate by more than a certain accuracy bound from the actual movement. Moreover, the different protocols enable several trade-offs between computational costs, communication cost, and the reduction in the trajectory data: Connection-Preserving Dead Reckoning minimizes the communication cost using dead reckoning, a technique originally designed for tracking an object's current position. Generic Remote Trajectory Simplification (GRTS) further separates between tracking of the current position and simplification of the past trajectory and can be realized with different line simplification algorithms. For both protocols, we discuss how to bound the space consumption and computing time at the moving object and thereby present an effective compression technique to optimize the reduction performance of real-time line simplification in general. Our evaluations with hundreds of real GPS traces show that a realization of GRTS with a simple simplification heuristic reaches 85-90\% of the best possible reduction rate, given by retrospective offline simplification. A realization with the optimal line simplification algorithm by Imai and Iri even reaches more than 97\% of the best possible reduction rate.}, url = {http://www2.informatik.uni-stuttgart.de/cgi-bin/NCSTRL/NCSTRL_view.pl?id=ART-2011-11&engl=1} } @article {ART-2011-01, author = {Muhammad Adnan Tariq and Boris Koldehofe and Gerald G. Koch and Imran Khan and Kurt Rothermel}, title = {{Meeting subscriber-defined QoS constraints in publish/subscribe systems}}, journal = {Concurrency and Computation: Practice and Experience}, publisher = {John Wiley \& Sons, Ltd.}, volume = {23}, number = {17}, pages = {2140--2153}, type = {Article in Journal}, month = {May}, year = {2011}, doi = {10.1002/cpe.1751}, keywords = {Content-based; P2P; Event-based; Bandwidth; End-to-end Delay; Spatial indexing; QoS}, language = {English}, cr-category = {C.2.4 Distributed Systems}, ee = {ftp://ftp.informatik.uni-stuttgart.de/pub/library/ncstrl.ustuttgart_fi/ART-2011-01/ART-2011-01.pdf, http://dx.doi.org/10.1002/cpe.1751}, department = {University of Stuttgart, Institute of Parallel and Distributed Systems, Distributed Systems}, abstract = {Current distributed publish/subscribe systems assume that all participants have similar QoS requirements and equally contribute to the system's resources. However, in many real-world applications, the message delay tolerance of individual peers may differ widely. Disseminating messages according to individual delay requirements not only allows for the satisfaction of user-specific needs but also significantly improves the utilization of the resources in a publish/subscribe system. In this paper, we propose a peer-to-peer-based approach to satisfy the individual delay requirements of subscribers in the presence of bandwidth constraints. Our approach allows subscribers to dynamically adjust the granularity of their subscriptions according to their bandwidth constraints and delay requirements. Subscribers maintain the publish/subscribe overlay in a decentralized manner by establishing connections to peers that provide messages meeting exactly their subscription granularity and complying to their delay requirements. Evaluations show that for practical workloads, the proposed system scales up to a large number of subscribers and performs robustly in a very dynamic setting.}, url = {http://www2.informatik.uni-stuttgart.de/cgi-bin/NCSTRL/NCSTRL_view.pl?id=ART-2011-01&engl=1} }