8 Search Results for "Jensen, Christian S."

Document
Invited Paper
DOI: 10.4230/LIPIcs.TIME.2018.2
Database Technology for Processing Temporal Data (Invited Paper)

Authors: Michael H. Böhlen, Anton Dignös, Johann Gamper, and Christian S. Jensen

Published in: LIPIcs, Volume 120, 25th International Symposium on Temporal Representation and Reasoning (TIME 2018)

Abstract
Despite the ubiquity of temporal data and considerable research on processing such data, database systems largely remain designed for processing the current state of some modeled reality. More recently, we have seen an increasing interest in processing historical or temporal data. The SQL:2011 standard introduced some temporal features, and commercial database management systems have started to offer temporal functionalities in a step-by-step manner. There has also been a proposal for a more fundamental and comprehensive solution for sequenced temporal queries, which allows a tight integration into relational database systems, thereby taking advantage of existing query optimization and evaluation technologies. New challenges for processing temporal data arise with multiple dimensions of time and the increasing amounts of data, including time series data that represent a special kind of temporal data.
Cite as

Michael H. Böhlen, Anton Dignös, Johann Gamper, and Christian S. Jensen. Database Technology for Processing Temporal Data (Invited Paper). In 25th International Symposium on Temporal Representation and Reasoning (TIME 2018). Leibniz International Proceedings in Informatics (LIPIcs), Volume 120, pp. 2:1-2:7, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2018)

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@InProceedings{bohlen_et_al:LIPIcs.TIME.2018.2,
  author =	{B\"{o}hlen, Michael H. and Dign\"{o}s, Anton and Gamper, Johann and Jensen, Christian S.},
  title =	{{Database Technology for Processing Temporal Data}},
  booktitle =	{25th International Symposium on Temporal Representation and Reasoning (TIME 2018)},
  pages =	{2:1--2:7},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-089-7},
  ISSN =	{1868-8969},
  year =	{2018},
  volume =	{120},
  editor =	{Alechina, Natasha and N{\o}rv\r{a}g, Kjetil and Penczek, Wojciech},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops-dev.dagstuhl.de/entities/document/10.4230/LIPIcs.TIME.2018.2},
  URN =		{urn:nbn:de:0030-drops-97674},
  doi =		{10.4230/LIPIcs.TIME.2018.2},
  annote =	{Keywords: Temporal databases, temporal query processing, sequenced semantics, SQL}
}
Document
DOI: 10.4230/LIPIcs.ESA.2017.47
Path-Contractions, Edge Deletions and Connectivity Preservation

Authors: Gregory Gutin, M. S. Ramanujan, Felix Reidl, and Magnus Wahlström

Published in: LIPIcs, Volume 87, 25th Annual European Symposium on Algorithms (ESA 2017)

Abstract
We study several problems related to graph modification problems under connectivity constraints from the perspective of parameterized complexity: (Weighted) Biconnectivity Deletion, where we are tasked with deleting k edges while preserving biconnectivity in an undirected graph, Vertexdeletion Preserving Strong Connectivity, where we want to maintain strong connectivity of a digraph while deleting exactly k vertices, and Path-contraction Preserving Strong Connectivity, in which the operation of path contraction on arcs is used instead. The parameterized tractability of this last problem was posed in [Bang-Jensen and Yeo, Discrete Applied Math 2008] as an open question and we answer it here in the negative: both variants of preserving strong connectivity are W[1]-hard. Preserving biconnectivity, on the other hand, turns out to be fixed parameter tractable (FPT) and we provide an FPT algorithm that solves Weighted Biconnectivity Deletion. Further, we show that the unweighted case even admits a randomized polynomial kernel. All our results provide further interesting data points for the systematic study of connectivitypreservation constraints in the parameterized setting.
Cite as

Gregory Gutin, M. S. Ramanujan, Felix Reidl, and Magnus Wahlström. Path-Contractions, Edge Deletions and Connectivity Preservation. In 25th Annual European Symposium on Algorithms (ESA 2017). Leibniz International Proceedings in Informatics (LIPIcs), Volume 87, pp. 47:1-47:13, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2017)

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@InProceedings{gutin_et_al:LIPIcs.ESA.2017.47,
  author =	{Gutin, Gregory and Ramanujan, M. S. and Reidl, Felix and Wahlstr\"{o}m, Magnus},
  title =	{{Path-Contractions, Edge Deletions and Connectivity Preservation}},
  booktitle =	{25th Annual European Symposium on Algorithms (ESA 2017)},
  pages =	{47:1--47:13},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-049-1},
  ISSN =	{1868-8969},
  year =	{2017},
  volume =	{87},
  editor =	{Pruhs, Kirk and Sohler, Christian},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops-dev.dagstuhl.de/entities/document/10.4230/LIPIcs.ESA.2017.47},
  URN =		{urn:nbn:de:0030-drops-78270},
  doi =		{10.4230/LIPIcs.ESA.2017.47},
  annote =	{Keywords: connectivity, strong connectivity, vertex deletion, arc contraction}
}
Document
DOI: 10.4230/DagSemProc.05421.1
05421 Abstracts Collection – Data Always and Everywhere – Management of Mobile, Ubiquitous, Pervasive, and Sensor Data

Authors: Gustavo Alonso, Christian S. Jensen, and Bernhard Mitschang

Published in: Dagstuhl Seminar Proceedings, Volume 5421, Data Always and Everywhere - Management of Mobile, Ubiquitous, Pervasive, and Sensor Data (2006)

Abstract
From 16.10.05 to 21.10.05, the Dagstuhl Seminar 05421, Data Always and Everywhere - Management of Mobile, Ubiquitous, Pervasive, and Sensor Data, was held in the International Conference and Research Center, Schloss Dagstuhl. During the seminar, all participants were given the opportunity to present their current research, and ongoing activities and open problems were discussed. This document is a collection of the abstracts of the presentations given during the seminar. Some abstracts offer links to extended abstracts, full papers, and other supporting documents. A separate companion document summarizes the seminar. The authors wish to acknowledge Victor Teixeira de Almeida, who served as collector for the seminar and thus played a key role in collecting materials from the seminar participants.
Cite as

Gustavo Alonso, Christian S. Jensen, and Bernhard Mitschang. 05421 Abstracts Collection – Data Always and Everywhere – Management of Mobile, Ubiquitous, Pervasive, and Sensor Data. In Data Always and Everywhere - Management of Mobile, Ubiquitous, Pervasive, and Sensor Data. Dagstuhl Seminar Proceedings, Volume 5421, pp. 1-19, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2006)

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@InProceedings{alonso_et_al:DagSemProc.05421.1,
  author =	{Alonso, Gustavo and Jensen, Christian S. and Mitschang, Bernhard},
  title =	{{05421 Abstracts Collection – Data Always and Everywhere – Management of Mobile, Ubiquitous, Pervasive, and Sensor Data}},
  booktitle =	{Data Always and Everywhere - Management of Mobile, Ubiquitous, Pervasive, and Sensor Data},
  pages =	{1--19},
  series =	{Dagstuhl Seminar Proceedings (DagSemProc)},
  ISSN =	{1862-4405},
  year =	{2006},
  volume =	{5421},
  editor =	{Gustavo Alonso and Christian S. Jensen and Bernhard Mitschang},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops-dev.dagstuhl.de/entities/document/10.4230/DagSemProc.05421.1},
  URN =		{urn:nbn:de:0030-drops-7966},
  doi =		{10.4230/DagSemProc.05421.1},
  annote =	{Keywords: Mobile ubiquitous and pervasive computing, sensor data, data streams, content integration, replication, caching, and consistency, service orientation, query and update processing, indexing, tracking process models, peer-to-peer computing, mobile ad-hoc networking, context awareness and preferences, moving objects, location--based mobile services,}
}
Document
DOI: 10.4230/DagSemProc.05421.2
05421 Executive Summary – Data Always and Everywhere – Management of Mobile, Ubiquitous, and Pervasive Data

Authors: Gustavo Alonso, Christian S. Jensen, and Bernhard Mitschang

Published in: Dagstuhl Seminar Proceedings, Volume 5421, Data Always and Everywhere - Management of Mobile, Ubiquitous, Pervasive, and Sensor Data (2006)

Abstract
This report summarizes the important aspects of the workshop on "Management of Mobile, Ubiquitous, and Pervasive Data", which took place from October 16th to October 21st, 2005. Thirty-seven participants from thirteen countries met during that week and discussed a broad range of topics related to the management of data in relation to mobile, ubiquitous, and pervasive applications of information technology. The wealth of the contributions is available at the seminar page at the Dagstuhl server. Here, we provide a short overview.
Cite as

Gustavo Alonso, Christian S. Jensen, and Bernhard Mitschang. 05421 Executive Summary – Data Always and Everywhere – Management of Mobile, Ubiquitous, and Pervasive Data. In Data Always and Everywhere - Management of Mobile, Ubiquitous, Pervasive, and Sensor Data. Dagstuhl Seminar Proceedings, Volume 5421, pp. 1-6, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2006)

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@InProceedings{alonso_et_al:DagSemProc.05421.2,
  author =	{Alonso, Gustavo and Jensen, Christian S. and Mitschang, Bernhard},
  title =	{{05421 Executive Summary – Data Always and Everywhere – Management of Mobile, Ubiquitous, and Pervasive Data}},
  booktitle =	{Data Always and Everywhere - Management of Mobile, Ubiquitous, Pervasive, and Sensor Data},
  pages =	{1--6},
  series =	{Dagstuhl Seminar Proceedings (DagSemProc)},
  ISSN =	{1862-4405},
  year =	{2006},
  volume =	{5421},
  editor =	{Gustavo Alonso and Christian S. Jensen and Bernhard Mitschang},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops-dev.dagstuhl.de/entities/document/10.4230/DagSemProc.05421.2},
  URN =		{urn:nbn:de:0030-drops-7947},
  doi =		{10.4230/DagSemProc.05421.2},
  annote =	{Keywords: Mobile Data Management, Ubiquitous Computing, Pervasive Computing, Streaming Data, Middleware, Data Integration, Data Placement, Ad-hoc Networking, Mi}
}
Document
DOI: 10.4230/DagSemProc.05421.3
B-tree indexes for high update rates

Authors: Goetz Graefe

Published in: Dagstuhl Seminar Proceedings, Volume 5421, Data Always and Everywhere - Management of Mobile, Ubiquitous, Pervasive, and Sensor Data (2006)

Abstract
In some applications, data capture dominates query processing. For example, monitoring moving objects often requires more insertions and updates than queries. Data gathering using automated sensors often exhibits this imbalance. More generally, indexing streams apparently is considered an unsolved problem. For those applications, B-tree indexes are reasonable choices if some trade-off decisions are tilted towards optimization of updates rather than of queries. This paper surveys techniques that let B-trees sustain very high update rates, up to multiple orders of magnitude higher than tradi-tional B-trees, at the expense of query processing performance. Perhaps not surprisingly, some of these techniques are reminiscent of those employed during index creation, index rebuild, etc., while others are derived from other well known technologies such as differential files and log-structured file systems.
Cite as

Goetz Graefe. B-tree indexes for high update rates. In Data Always and Everywhere - Management of Mobile, Ubiquitous, Pervasive, and Sensor Data. Dagstuhl Seminar Proceedings, Volume 5421, pp. 1-7, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2006)

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@InProceedings{graefe:DagSemProc.05421.3,
  author =	{Graefe, Goetz},
  title =	{{B-tree indexes for high update rates}},
  booktitle =	{Data Always and Everywhere - Management of Mobile, Ubiquitous, Pervasive, and Sensor Data},
  pages =	{1--7},
  series =	{Dagstuhl Seminar Proceedings (DagSemProc)},
  ISSN =	{1862-4405},
  year =	{2006},
  volume =	{5421},
  editor =	{Gustavo Alonso and Christian S. Jensen and Bernhard Mitschang},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops-dev.dagstuhl.de/entities/document/10.4230/DagSemProc.05421.3},
  URN =		{urn:nbn:de:0030-drops-7632},
  doi =		{10.4230/DagSemProc.05421.3},
  annote =	{Keywords: B-tree, high update rates}
}
Document
DOI: 10.4230/DagSemProc.05421.4
Media Distribution in a Pervasive Computing Environment

Authors: Alexander Sinitsyn, Winfried A. H. Berkvens, Arjan Claassen, and Joep P. van Gassel

Published in: Dagstuhl Seminar Proceedings, Volume 5421, Data Always and Everywhere - Management of Mobile, Ubiquitous, Pervasive, and Sensor Data (2006)

Abstract
Distribution of media in the fast growing world of digital stored content and multimedia supporting devices with connectivity, calls for a new media distribution architecture. The user should be provided with the experience of having an overview of his full media collection, regardless of the time, the place, and the connectivity. Transparent distributed data management is crucial to Ambient Intelligent applications. The proposed media distribution architecture offers a possible solution. It provides the user with the experience of having all his media collections available at any time, in any place, and managing them regardless of connection availability in the heterogeneous environment. This experience is enabled in our system by the separation of metadata and content handling. Other features are efficient handling of snapshots, usage of various database technologies, and leveraging device and service discovery mechanisms.
Cite as

Alexander Sinitsyn, Winfried A. H. Berkvens, Arjan Claassen, and Joep P. van Gassel. Media Distribution in a Pervasive Computing Environment. In Data Always and Everywhere - Management of Mobile, Ubiquitous, Pervasive, and Sensor Data. Dagstuhl Seminar Proceedings, Volume 5421, pp. 1-5, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2006)

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@InProceedings{sinitsyn_et_al:DagSemProc.05421.4,
  author =	{Sinitsyn, Alexander and Berkvens, Winfried A. H. and Claassen, Arjan and van Gassel, Joep P.},
  title =	{{Media Distribution in a Pervasive Computing Environment}},
  booktitle =	{Data Always and Everywhere - Management of Mobile, Ubiquitous, Pervasive, and Sensor Data},
  pages =	{1--5},
  series =	{Dagstuhl Seminar Proceedings (DagSemProc)},
  ISSN =	{1862-4405},
  year =	{2006},
  volume =	{5421},
  editor =	{Gustavo Alonso and Christian S. Jensen and Bernhard Mitschang},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops-dev.dagstuhl.de/entities/document/10.4230/DagSemProc.05421.4},
  URN =		{urn:nbn:de:0030-drops-7622},
  doi =		{10.4230/DagSemProc.05421.4},
  annote =	{Keywords: Data management}
}
Document
DOI: 10.4230/DagSemProc.04441.6
04441 Working Group – Research Issues in Mobile Querying

Authors: Martin Breunig and Christian S. Jensen

Published in: Dagstuhl Seminar Proceedings, Volume 4441, Mobile Information Management (2005)

Abstract
This document reports on key aspects of the discussions conducted within the working group. In particular, the document aims to offer a structured and somewhat digested summary of the group's discussions. The document first offers concepts that enable characterization of "mobile queries'' as well as the types of systems that enable such queries. It explores the notion of context in mobile queries. The document ends with a few observations, mainly regarding challenges.
Cite as

Martin Breunig and Christian S. Jensen. 04441 Working Group – Research Issues in Mobile Querying. In Mobile Information Management. Dagstuhl Seminar Proceedings, Volume 4441, pp. 1-6, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2005)

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@InProceedings{breunig_et_al:DagSemProc.04441.6,
  author =	{Breunig, Martin and Jensen, Christian S.},
  title =	{{04441 Working Group – Research Issues in Mobile Querying}},
  booktitle =	{Mobile Information Management},
  pages =	{1--6},
  series =	{Dagstuhl Seminar Proceedings (DagSemProc)},
  ISSN =	{1862-4405},
  year =	{2005},
  volume =	{4441},
  editor =	{Margaret H. Dunham and Birgitta K\"{o}nig-Ries and Evaggelia Pitoura and Peter Reiher and Can T\"{u}rker},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops-dev.dagstuhl.de/entities/document/10.4230/DagSemProc.04441.6},
  URN =		{urn:nbn:de:0030-drops-1651},
  doi =		{10.4230/DagSemProc.04441.6},
  annote =	{Keywords: Mobile Queries}
}
Document
DOI: 10.4230/DagSemProc.04441.8
04441 Working Group – Towards a Handbook for User-Centred Mobile Application Design

Authors: Susanne Boll, Martin Breunig, Nigel Davies, Christian S. Jensen, Birgitta König-Ries, Rainer Malaka, Florian Matthes, Christoforos Panayiotou, Simonas Saltenis, and Thomas Schwarz

Published in: Dagstuhl Seminar Proceedings, Volume 4441, Mobile Information Management (2005)

Abstract
Why do we have difficulties designing mobile apps? Is there a "Mobile RUP"?
Cite as

Susanne Boll, Martin Breunig, Nigel Davies, Christian S. Jensen, Birgitta König-Ries, Rainer Malaka, Florian Matthes, Christoforos Panayiotou, Simonas Saltenis, and Thomas Schwarz. 04441 Working Group – Towards a Handbook for User-Centred Mobile Application Design. In Mobile Information Management. Dagstuhl Seminar Proceedings, Volume 4441, pp. 1-8, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2005)

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@InProceedings{boll_et_al:DagSemProc.04441.8,
  author =	{Boll, Susanne and Breunig, Martin and Davies, Nigel and Jensen, Christian S. and K\"{o}nig-Ries, Birgitta and Malaka, Rainer and Matthes, Florian and Panayiotou, Christoforos and Saltenis, Simonas and Schwarz, Thomas},
  title =	{{04441 Working Group – Towards a Handbook for User-Centred Mobile Application Design}},
  booktitle =	{Mobile Information Management},
  pages =	{1--8},
  series =	{Dagstuhl Seminar Proceedings (DagSemProc)},
  ISSN =	{1862-4405},
  year =	{2005},
  volume =	{4441},
  editor =	{Margaret H. Dunham and Birgitta K\"{o}nig-Ries and Evaggelia Pitoura and Peter Reiher and Can T\"{u}rker},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops-dev.dagstuhl.de/entities/document/10.4230/DagSemProc.04441.8},
  URN =		{urn:nbn:de:0030-drops-1662},
  doi =		{10.4230/DagSemProc.04441.8},
  annote =	{Keywords: User-Centred Mobile Application Design}
}
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