@inproceedings {INPROC-2014-31,
   author = {Beate Ottenw{\"a}lder and Boris Koldehofe and Kurt Rothermel and Kirak Hong and Umakishore Ramachandran},
   title = {{RECEP: Selection-based Reuse for Distributed Complex Event Processing}},
   booktitle = {Proceedings of the 8th ACM International Conference on Distributed Event-Based Systems (DEBS 2014)},
   publisher = {ACM},
   institution = {University of Stuttgart, Faculty of Computer Science, Electrical Engineering, and Information Technology, Germany},
   pages = {59--70},
   type = {Conference Paper},
   month = {May},
   year = {2014},
   doi = {10.1145/2611286.2611297},
   keywords = {mobility; complex event processing; query optimization},
   language = {English},
   cr-category = {C.2.1 Network Architecture and Design,     C.2.4 Distributed Systems},
   ee = {ftp://ftp.informatik.uni-stuttgart.de/pub/library/ncstrl.ustuttgart_fi/INPROC-2014-31/INPROC-2014-31.pdf},
   department = {University of Stuttgart, Institute of Parallel and Distributed Systems, Distributed Systems},
   abstract = {An appealing use case of complex event processing (CEP) systems is for mobile users to react in real-time to events in their environment, e.g., to the occurrence of a dangerous situation such as an accident. Maintaining mobile CEP systems is highly resource intensive since in many cases events need to be detected in a consumer-centric manner to ensure low latency event detection and high quality of results. In this paper we propose the RECEP system to increase the scalability of mobile CEP systems. In the presence of mobile users with partially overlapping interest, the RECEP system offers methods to efficiently reuse computations and this way reduces the resource requirements of mobile CEP. Since reuse of computations happens with respect to well defined quality metrics, RECEP can be easily tailored to specific mobile applications and maximize the resource savings for their desired quality in terms of precision and recall of the processed events from the user's environment.},
   url = {http://www2.informatik.uni-stuttgart.de/cgi-bin/NCSTRL/NCSTRL_view.pl?id=INPROC-2014-31&engl=1}
}
@inproceedings {INPROC-2013-62,
   author = {Kirak Hong and Beate Ottenw{\"a}lder and Umakishore Ramachandran},
   title = {{Scalable Spatio-temporal Analysis on Distributed Camera Networks}},
   booktitle = {Proceedings of the 7th International Symposium on Intelligent Distributed Computing (IDC 2013)},
   publisher = {Springer International Publishing},
   institution = {University of Stuttgart, Faculty of Computer Science, Electrical Engineering, and Information Technology, Germany},
   series = {Studies in Computational Intelligence},
   volume = {511},
   pages = {131--140},
   type = {Conference Paper},
   month = {September},
   year = {2013},
   doi = {10.1007/978-3-319-01571-2_16},
   language = {English},
   cr-category = {C.2.4 Distributed Systems},
   ee = {ftp://ftp.informatik.uni-stuttgart.de/pub/library/ncstrl.ustuttgart_fi/INPROC-2013-62/INPROC-2013-62.pdf,     http://link.springer.com/chapter/10.1007/978-3-319-01571-2_16},
   department = {University of Stuttgart, Institute of Parallel and Distributed Systems, Distributed Systems},
   abstract = {Technological advances and the low cost of sensors enable the deployment of large-scale camera networks in airports and metropolises. A well-known technique, called spatio-temporal analysis, enables detecting anomalies such as an individual entering into a restricted area without permission. Spatio-temporal analysis requires a large amount of system resources to infer locations of occupants in real-time. In particular, state update becomes a bottleneck due to computation and communication overhead to update possibly large application state. In this paper we propose a system design and mechanisms for scalable spatio-temporal analysis. We present a distributed system architecture including smart cameras and distributed worker nodes in the cloud to enable real-time spatio-temporal analysis on large-scale camera networks. Furthermore we propose and implement a couple of selective update mechanisms to further improve scalability of our system by reducing the communication cost for state update.},
   url = {http://www2.informatik.uni-stuttgart.de/cgi-bin/NCSTRL/NCSTRL_view.pl?id=INPROC-2013-62&engl=1}
}
@inproceedings {INPROC-2013-31,
   author = {Kirak Hong and David Lillethun and Umakishore Ramachandran and Beate Ottenw{\"a}lder and Boris Koldehofe},
   title = {{Mobile Fog: A Programming Model for Large-Scale Applications on the Internet of Things}},
   booktitle = {Proceedings of the 2nd MCC Workshop on Mobile Cloud Computing},
   address = {Hong Kong, China},
   publisher = {ACM Press},
   institution = {University of Stuttgart, Faculty of Computer Science, Electrical Engineering, and Information Technology, Germany},
   pages = {15--20},
   type = {Conference Paper},
   month = {August},
   year = {2013},
   doi = {10.1145/2491266.2491270},
   keywords = {fog computing; cloud computing; programming model; Internet of Things; future Internet applications; situation awareness applications},
   language = {English},
   cr-category = {C.2.1 Network Architecture and Design,     C.2.4 Distributed Systems},
   ee = {ftp://ftp.informatik.uni-stuttgart.de/pub/library/ncstrl.ustuttgart_fi/INPROC-2013-31/INPROC-2013-31.pdf,     http://doi.acm.org/10.1145/2491266.2491270},
   department = {University of Stuttgart, Institute of Parallel and Distributed Systems, Distributed Systems},
   abstract = {The ubiquitous deployment of mobile and sensor devices is creating a new environment, namely the Internet of Things(IoT), that enables a wide range of future Internet applications. In this work, we present Mobile Fog, a high level programming model for future Internet applications that are geospatially distributed, large-scale, and latency-sensitive. We analyze use cases for the programming model with camera network and connected vehicle applications to show the efficacy of Mobile Fog We also evaluate application performance through simulation.},
   url = {http://www2.informatik.uni-stuttgart.de/cgi-bin/NCSTRL/NCSTRL_view.pl?id=INPROC-2013-31&engl=1}
}
@inproceedings {INPROC-2013-29,
   author = {Kirak Hong and David Lillethun and Umakishore Ramachandran and Beate Ottenw{\"a}lder and Boris Koldehofe},
   title = {{Opportunistic Spatio-temporal Event Processing for Mobile Situation Awareness}},
   booktitle = {Proceedings of the 7th ACM International Conference on Distributed Event-Based Systems (DEBS)},
   address = {Arlington, Texas, USA},
   publisher = {ACM Press},
   institution = {University of Stuttgart, Faculty of Computer Science, Electrical Engineering, and Information Technology, Germany},
   pages = {195--206},
   type = {Conference Paper},
   month = {June},
   year = {2013},
   doi = {10.1145/2488222.2488266},
   keywords = {mobility; complex event processing; situation awareness},
   language = {English},
   cr-category = {C.2.1 Network Architecture and Design,     C.2.4 Distributed Systems},
   ee = {ftp://ftp.informatik.uni-stuttgart.de/pub/library/ncstrl.ustuttgart_fi/INPROC-2013-29/INPROC-2013-29.pdf,     http://doi.acm.org/10.1145/2488222.2488266},
   department = {University of Stuttgart, Institute of Parallel and Distributed Systems, Distributed Systems},
   abstract = {With the proliferation of mobile devices and sensors, mobile situation awareness is becoming an important class of applications. The key requirement of this class of applications is low-latency processing of events stemming from sensordata in order to provide timely situational information to mobile users.To satisfy the latency requirement, we propose a spatio-temporal event processing system that uses prediction-based continuous query handling. Our system predicts future query regions for moving consumers and starts processing events early so that the live situational information is available when the consumer reaches the future location. In contrast to existing systems, our system provides timely information about a consumer's current position by hiding computation latency for processing recent events. To evaluate our system, we measure the quality of results and timeliness of live situational information with various query parameters. Our evaluation shows that we can achieve highly meaningful query results with near-zero latency in most cases.},
   url = {http://www2.informatik.uni-stuttgart.de/cgi-bin/NCSTRL/NCSTRL_view.pl?id=INPROC-2013-29&engl=1}
}
@inproceedings {INPROC-2013-28,
   author = {Beate Ottenw{\"a}lder and Boris Koldehofe and Kurt Rothermel and Umakishore Ramachandran},
   title = {{MigCEP: Operator Migration for Mobility Driven Distributed Complex Event Processing}},
   booktitle = {Proceedings of the 7th ACM International Conference on Distributed Event-Based Systems (DEBS)},
   address = {Arlington, Texas, USA},
   publisher = {ACM Press},
   institution = {University of Stuttgart, Faculty of Computer Science, Electrical Engineering, and Information Technology, Germany},
   pages = {183--194},
   type = {Conference Paper},
   month = {June},
   year = {2013},
   doi = {10.1145/2488222.2488265},
   keywords = {complex event processing; migration; mobility},
   language = {English},
   cr-category = {C.2.1 Network Architecture and Design,     C.2.4 Distributed Systems,     E.1 Data Structures},
   ee = {ftp://ftp.informatik.uni-stuttgart.de/pub/library/ncstrl.ustuttgart_fi/INPROC-2013-28/INPROC-2013-28.pdf,     http://doi.acm.org/10.1145/2488222.2488265},
   department = {University of Stuttgart, Institute of Parallel and Distributed Systems, Distributed Systems},
   abstract = {A recent trend in communication networks --- sometimes referred to as fog computing --- offers to execute computational tasks close to the access points of the networks. This enables real-time applications, like mobile Complex Event Processing (CEP), to significantly reduce end-to-end latencies and bandwidth usage. Most work studying the placement of operators in such an environment completely disregards the migration costs. However, the mobility of users requires frequent migration of operators, together with possibly large state information, to meet latency restrictions and save bandwidth in the infrastructure. This paper presents a placement and migration method for providers of infrastructures that incorporate cloud and fog resources. It ensures application-defined end-to-end latency restrictions and reduces the network utilization by planning the migration ahead of time. Furthermore, we present how the application knowledge of the CEP system can be used to improve current live migration techniques for Virtual Machines to reduce the required bandwidth during the migration. Our evaluations show that we safe up to 49\% of the network utilization with perfect knowledge about a users mobility pattern and up to 27\% of the network utilization when considering the uncertainty of those patterns.},
   url = {http://www2.informatik.uni-stuttgart.de/cgi-bin/NCSTRL/NCSTRL_view.pl?id=INPROC-2013-28&engl=1}
}
@inproceedings {INPROC-2012-20,
   author = {Boris Koldehofe and Beate Ottenw{\"a}lder and Kurt Rothermel and Umakishore Ramachandran},
   title = {{Moving Range Queries in Distributed Complex Event Processing}},
   booktitle = {Proceedings of the 6th ACM International Conference on Distributed Event-Based Systems (DEBS).},
   address = {Berlin},
   publisher = {ACM},
   institution = {University of Stuttgart, Faculty of Computer Science, Electrical Engineering, and Information Technology, Germany},
   pages = {201--212},
   type = {Conference Paper},
   month = {July},
   year = {2012},
   doi = {10.1145/2335484.2335507},
   keywords = {Complex Event Processing; Event-based systems; Moving range queries},
   language = {English},
   cr-category = {C.2.4 Distributed Systems},
   ee = {ftp://ftp.informatik.uni-stuttgart.de/pub/library/ncstrl.ustuttgart_fi/INPROC-2012-20/INPROC-2012-20.pdf,     http://doi.acm.org/10.1145/2335484.2335507},
   department = {University of Stuttgart, Institute of Parallel and Distributed Systems, Distributed Systems},
   abstract = {Up to now correlations in complex event processing (CEP) systems are detected by a well defined set of operators whose configuration is determined ahead of deployment time. Although CEP operators involve location specific attributes, state of the art systems are heavily constraint in detecting situations where the interest in a situation changes dependent on the consumer's location, e.g., with the movement of mobile devices. This paper adopts the concept of range queries to CEP systems. We propose a mobility-aware event delivery semantic and present a corresponding execution model that accounts for mobility driven selection of primary event streams to the CEP system. By utilizing the properties of this execution model we derive an algorithm that establishes low cost and coordinated reconfiguration of CEP operators in a distributed system. The algorithm minimizes the amount of information that needs to be streamed between operators and avoids additional delays as a result of a reconfiguration of CEP operators. We present an analysis of the algorithm's properties and evaluate the efficiency of the proposed reconfiguration algorithm.},
   url = {http://www2.informatik.uni-stuttgart.de/cgi-bin/NCSTRL/NCSTRL_view.pl?id=INPROC-2012-20&engl=1}
}
@article {ART-2014-07,
   author = {Beate Ottenw{\"a}lder and Boris Koldehofe and Kurt Rothermel and Kirak Hong and David Lillethun and Umakishore Ramachandran},
   title = {{MCEP: A Mobility-Aware Complex Event Processing System}},
   journal = {ACM Transactions Internet Technology},
   editor = {Munindar P. Singh},
   publisher = {ACM},
   volume = {14},
   number = {1},
   pages = {1--24},
   type = {Article in Journal},
   month = {August},
   year = {2014},
   issn = {1533-5399 EISSN:1557-6051},
   keywords = {Mobility, complex event processing, migration, moving range queries},
   language = {English},
   cr-category = {C.2.1 Network Architecture and Design,     C.2.4 Distributed Systems},
   ee = {http://doi.acm.org/10.1145/2633688},
   department = {University of Stuttgart, Institute of Parallel and Distributed Systems, Distributed Systems},
   abstract = {With the proliferation of mobile devices and sensors, complex event processing (CEP) is becoming increasingly important to scalably detect situations in real time. Current CEP systems are not capable of dealing efficiently with highly dynamic mobile consumers whose interests change with their location. We introduce the distributed mobile CEP (MCEP) system which automatically adapts the processing of events according to a consumer's location. MCEP significantly reduces latency, network utilization, and processing overhead by providing on-demand and opportunistic adaptation algorithms to dynamically assign event streams and computing resources to operators of the MCEP system.},
   url = {http://www2.informatik.uni-stuttgart.de/cgi-bin/NCSTRL/NCSTRL_view.pl?id=ART-2014-07&engl=1}
}