4 Search Results for "Mitchell, John C."


Document
The Geodesic Edge Center of a Simple Polygon

Authors: Anna Lubiw and Anurag Murty Naredla

Published in: LIPIcs, Volume 258, 39th International Symposium on Computational Geometry (SoCG 2023)


Abstract
The geodesic edge center of a polygon is a point c inside the polygon that minimizes the maximum geodesic distance from c to any edge of the polygon, where geodesic distance is the shortest path distance inside the polygon. We give a linear-time algorithm to find a geodesic edge center of a simple polygon. This improves on the previous O(n log n) time algorithm by Lubiw and Naredla [European Symposium on Algorithms, 2021]. The algorithm builds on an algorithm to find the geodesic vertex center of a simple polygon due to Pollack, Sharir, and Rote [Discrete & Computational Geometry, 1989] and an improvement to linear time by Ahn, Barba, Bose, De Carufel, Korman, and Oh [Discrete & Computational Geometry, 2016]. The geodesic edge center can easily be found from the geodesic farthest-edge Voronoi diagram of the polygon. Finding that Voronoi diagram in linear time is an open question, although the geodesic nearest edge Voronoi diagram (the medial axis) can be found in linear time. As a first step of our geodesic edge center algorithm, we give a linear-time algorithm to find the geodesic farthest-edge Voronoi diagram restricted to the polygon boundary.

Cite as

Anna Lubiw and Anurag Murty Naredla. The Geodesic Edge Center of a Simple Polygon. In 39th International Symposium on Computational Geometry (SoCG 2023). Leibniz International Proceedings in Informatics (LIPIcs), Volume 258, pp. 49:1-49:15, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2023)


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@InProceedings{lubiw_et_al:LIPIcs.SoCG.2023.49,
  author =	{Lubiw, Anna and Naredla, Anurag Murty},
  title =	{{The Geodesic Edge Center of a Simple Polygon}},
  booktitle =	{39th International Symposium on Computational Geometry (SoCG 2023)},
  pages =	{49:1--49:15},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-273-0},
  ISSN =	{1868-8969},
  year =	{2023},
  volume =	{258},
  editor =	{Chambers, Erin W. and Gudmundsson, Joachim},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops-dev.dagstuhl.de/entities/document/10.4230/LIPIcs.SoCG.2023.49},
  URN =		{urn:nbn:de:0030-drops-178994},
  doi =		{10.4230/LIPIcs.SoCG.2023.49},
  annote =	{Keywords: geodesic center of polygon, farthest edges, farthest-segment Voronoi diagram}
}
Document
Massively Open Online Courses, Current State and Perspectives (Dagstuhl Perspectives Workshop 14112)

Authors: Pierre Dillenbourg, Claude Kirchner, John C. Mitchell, and Martin Wirsing

Published in: Dagstuhl Reports, Volume 4, Issue 3 (2014)


Abstract
The Perspectives Workshop on "Massively Open Online Courses, Current State and Perspectives" took place at Schloss Dagstuhl on March 10--13, 2014. Twenty-three leading researchers and practitioners from informatics and pedagogical sciences presented and discussed current experiences and future directions, challenges, and visions for the influence of MOOCs on university teaching and learning. The first day of the workshop consisted of a series of presentations in which each participant presented those topics and developments he or she considered most relevant for the future development of MOOCs. The abstracts of these talks are given in the first part of this report. On the second and third day the participants divided into several working groups according to the main thematic areas that had been identified on the first day. This gives rise to a Manifesto to be published in the Dagstuhl Manifesto series and to identifying main research questions rised by the emergence of MOOCs: they are summarized in the second part of this report.

Cite as

Pierre Dillenbourg, Claude Kirchner, John C. Mitchell, and Martin Wirsing. Massively Open Online Courses, Current State and Perspectives (Dagstuhl Perspectives Workshop 14112). In Dagstuhl Reports, Volume 4, Issue 3, pp. 47-61, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2014)


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@Article{dillenbourg_et_al:DagRep.4.3.47,
  author =	{Dillenbourg, Pierre and Kirchner, Claude and Mitchell, John C. and Wirsing, Martin},
  title =	{{Massively Open Online Courses, Current State and Perspectives (Dagstuhl Perspectives Workshop 14112)}},
  pages =	{47--61},
  journal =	{Dagstuhl Reports},
  ISSN =	{2192-5283},
  year =	{2014},
  volume =	{4},
  number =	{3},
  editor =	{Dillenbourg, Pierre and Kirchner, Claude and Mitchell, John C. and Wirsing, Martin},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops-dev.dagstuhl.de/entities/document/10.4230/DagRep.4.3.47},
  URN =		{urn:nbn:de:0030-drops-45910},
  doi =		{10.4230/DagRep.4.3.47},
  annote =	{Keywords: Massively open online courses, MOOC, SPOC, e-learning, education}
}
Document
Data-Oblivious Data Structures

Authors: John C. Mitchell and Joe Zimmerman

Published in: LIPIcs, Volume 25, 31st International Symposium on Theoretical Aspects of Computer Science (STACS 2014)


Abstract
An algorithm is called data-oblivious if its control flow and memory access pattern do not depend on its input data. Data-oblivious algorithms play a significant role in secure cloud computing, since programs that are run on secret data—as in fully homomorphic encryption or secure multi-party computation—must be data-oblivious. In this paper, we formalize three definitions of data-obliviousness that have appeared implicitly in the literature, explore their implications, and show separations. We observe that data-oblivious algorithms often compose well when viewed as data structures. Using this approach, we construct data-oblivious stacks, queues, and priority queues that are considerably simpler than existing constructions, as well as improving constan factors. We also establish a new upper bound for oblivious data compaction, and use this result to show that an "offline" variant of the Oblivious RAM problem can be solved with O(log(n).log(log(n))) expected amortized time per operation - as compared with O(log^2(n)/log(log(n))), the best known upper bound for the standard online formulation.

Cite as

John C. Mitchell and Joe Zimmerman. Data-Oblivious Data Structures. In 31st International Symposium on Theoretical Aspects of Computer Science (STACS 2014). Leibniz International Proceedings in Informatics (LIPIcs), Volume 25, pp. 554-565, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2014)


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@InProceedings{mitchell_et_al:LIPIcs.STACS.2014.554,
  author =	{Mitchell, John C. and Zimmerman, Joe},
  title =	{{Data-Oblivious Data Structures}},
  booktitle =	{31st International Symposium on Theoretical Aspects of Computer Science (STACS 2014)},
  pages =	{554--565},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-939897-65-1},
  ISSN =	{1868-8969},
  year =	{2014},
  volume =	{25},
  editor =	{Mayr, Ernst W. and Portier, Natacha},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops-dev.dagstuhl.de/entities/document/10.4230/LIPIcs.STACS.2014.554},
  URN =		{urn:nbn:de:0030-drops-44876},
  doi =		{10.4230/LIPIcs.STACS.2014.554},
  annote =	{Keywords: Data-oblivious algorithms, Data-oblivious data structures, Oblivious RAM, Secure multi-party computation, Secure cloud computing}
}
Document
09073 Abstracts Collection – Model-Based Design of Trustworthy Health Information Systems

Authors: Ruth Breu, John C. Mitchell, Janos Sztipanovits, and Alfred Winter

Published in: Dagstuhl Seminar Proceedings, Volume 9073, Model-Based Design of Trustworthy Health Information Systems (2009)


Abstract
The Dagstuhl Seminar ``Model-Based Design of Trustworthy Information Systems'' took place from February 11th to February 14th, 2009, at the International Conference and Research Center Schloss Dagstuhl. The goal of the seminar was to bring together experts from the domains of health care, software engineering and security in order to discuss the challenges of emerging health care scenarios. The seminar combined presentations with discussions in groups.

Cite as

Ruth Breu, John C. Mitchell, Janos Sztipanovits, and Alfred Winter. 09073 Abstracts Collection – Model-Based Design of Trustworthy Health Information Systems. In Model-Based Design of Trustworthy Health Information Systems. Dagstuhl Seminar Proceedings, Volume 9073, pp. 1-19, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2009)


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@InProceedings{breu_et_al:DagSemProc.09073.1,
  author =	{Breu, Ruth and Mitchell, John C. and Sztipanovits, Janos and Winter, Alfred},
  title =	{{09073 Abstracts Collection – Model-Based Design of Trustworthy Health Information Systems}},
  booktitle =	{Model-Based Design of Trustworthy Health Information Systems},
  pages =	{1--19},
  series =	{Dagstuhl Seminar Proceedings (DagSemProc)},
  ISSN =	{1862-4405},
  year =	{2009},
  volume =	{9073},
  editor =	{Ruth Breu and John C. Mitchell and Janos Sztipanovits and Alfred Winter},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops-dev.dagstuhl.de/entities/document/10.4230/DagSemProc.09073.1},
  URN =		{urn:nbn:de:0030-drops-19983},
  doi =		{10.4230/DagSemProc.09073.1},
  annote =	{Keywords: Trustworthy Systems, Health Information Systems, Model-Based Design, Security Policies, Service Oriented Architecture}
}
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