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Documents authored by Nöllenburg, Martin

Document
DOI: 10.4230/LIPIcs.GD.2024.12
The Parameterized Complexity Of Extending Stack Layouts

Authors: Thomas Depian, Simon D. Fink, Robert Ganian, and Martin Nöllenburg

Published in: LIPIcs, Volume 320, 32nd International Symposium on Graph Drawing and Network Visualization (GD 2024)

Abstract
An 𝓁-page stack layout (also known as an 𝓁-page book embedding) of a graph is a linear order of the vertex set together with a partition of the edge set into 𝓁 stacks (or pages), such that the endpoints of no two edges on the same stack alternate. We study the problem of extending a given partial 𝓁-page stack layout into a complete one, which can be seen as a natural generalization of the classical NP-hard problem of computing a stack layout of an input graph from scratch. Given the inherent intractability of the problem, we focus on identifying tractable fragments through the refined lens of parameterized complexity analysis. Our results paint a detailed and surprisingly rich complexity-theoretic landscape of the problem which includes the identification of paraNP-hard, W[1]-hard and XP-tractable, as well as fixed-parameter tractable fragments of stack layout extension via a natural sequence of parameterizations.
Cite as

Thomas Depian, Simon D. Fink, Robert Ganian, and Martin Nöllenburg. The Parameterized Complexity Of Extending Stack Layouts. In 32nd International Symposium on Graph Drawing and Network Visualization (GD 2024). Leibniz International Proceedings in Informatics (LIPIcs), Volume 320, pp. 12:1-12:17, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2024)

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@InProceedings{depian_et_al:LIPIcs.GD.2024.12,
  author =	{Depian, Thomas and Fink, Simon D. and Ganian, Robert and N\"{o}llenburg, Martin},
  title =	{{The Parameterized Complexity Of Extending Stack Layouts}},
  booktitle =	{32nd International Symposium on Graph Drawing and Network Visualization (GD 2024)},
  pages =	{12:1--12:17},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-343-0},
  ISSN =	{1868-8969},
  year =	{2024},
  volume =	{320},
  editor =	{Felsner, Stefan and Klein, Karsten},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.GD.2024.12},
  URN =		{urn:nbn:de:0030-drops-212960},
  doi =		{10.4230/LIPIcs.GD.2024.12},
  annote =	{Keywords: Stack Layout, Drawing Extension, Parameterized Complexity, Book Embedding}
}
Document
DOI: 10.4230/LIPIcs.GD.2024.15
Bundling-Aware Graph Drawing

Authors: Daniel Archambault, Giuseppe Liotta, Martin Nöllenburg, Tommaso Piselli, Alessandra Tappini, and Markus Wallinger

Published in: LIPIcs, Volume 320, 32nd International Symposium on Graph Drawing and Network Visualization (GD 2024)

Abstract
Edge bundling algorithms significantly improve the visualization of dense graphs by reducing the clutter of many edges visible on screen by bundling them together. As such, bundling is often viewed as a post-processing step applied to a drawing, and the vast majority of edge bundling algorithms consider a graph and its drawing as input. Another way of thinking about edge bundling is to simultaneously optimize both the drawing and the bundling. In this paper, we investigate methods to simultaneously optimize a graph drawing and its bundling. We describe an algorithmic framework which consists of three main steps, namely Filter, Draw, and Bundle. We then propose two alternative implementations and experimentally compare them against the state-of-the-art approach and the simple idea of drawing and subsequently bundling the graph. The experiments confirm that bundled drawings created by our framework outperform previous approaches according to standard quality metrics for edge bundling.
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Daniel Archambault, Giuseppe Liotta, Martin Nöllenburg, Tommaso Piselli, Alessandra Tappini, and Markus Wallinger. Bundling-Aware Graph Drawing. In 32nd International Symposium on Graph Drawing and Network Visualization (GD 2024). Leibniz International Proceedings in Informatics (LIPIcs), Volume 320, pp. 15:1-15:19, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2024)

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@InProceedings{archambault_et_al:LIPIcs.GD.2024.15,
  author =	{Archambault, Daniel and Liotta, Giuseppe and N\"{o}llenburg, Martin and Piselli, Tommaso and Tappini, Alessandra and Wallinger, Markus},
  title =	{{Bundling-Aware Graph Drawing}},
  booktitle =	{32nd International Symposium on Graph Drawing and Network Visualization (GD 2024)},
  pages =	{15:1--15:19},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-343-0},
  ISSN =	{1868-8969},
  year =	{2024},
  volume =	{320},
  editor =	{Felsner, Stefan and Klein, Karsten},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.GD.2024.15},
  URN =		{urn:nbn:de:0030-drops-212995},
  doi =		{10.4230/LIPIcs.GD.2024.15},
  annote =	{Keywords: Edge Bundling, Experimental Comparison, Graph Sparsification}
}
Document
DOI: 10.4230/LIPIcs.GD.2024.22
Boundary Labeling in a Circular Orbit

Authors: Annika Bonerath, Martin Nöllenburg, Soeren Terziadis, Markus Wallinger, and Jules Wulms

Published in: LIPIcs, Volume 320, 32nd International Symposium on Graph Drawing and Network Visualization (GD 2024)

Abstract
Boundary labeling is a well-known method for displaying short textual labels for a set of point features in a figure alongside the boundary of that figure. Labels and their corresponding points are connected via crossing-free leaders. We propose orbital boundary labeling as a new variant of the problem, in which (i) the figure is enclosed by a circular contour and (ii) the labels are placed as disjoint circular arcs in an annulus-shaped orbit around the contour. The algorithmic objective is to compute an orbital boundary labeling with the minimum total leader length. We identify several parameters that define the corresponding problem space: two leader types (straight or orbital-radial), label size and order, presence of candidate label positions, and constraints on where a leader attaches to its label. Our results provide polynomial-time algorithms for many variants and NP-hardness for others, using a variety of geometric and combinatorial insights.
Cite as

Annika Bonerath, Martin Nöllenburg, Soeren Terziadis, Markus Wallinger, and Jules Wulms. Boundary Labeling in a Circular Orbit. In 32nd International Symposium on Graph Drawing and Network Visualization (GD 2024). Leibniz International Proceedings in Informatics (LIPIcs), Volume 320, pp. 22:1-22:17, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2024)

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@InProceedings{bonerath_et_al:LIPIcs.GD.2024.22,
  author =	{Bonerath, Annika and N\"{o}llenburg, Martin and Terziadis, Soeren and Wallinger, Markus and Wulms, Jules},
  title =	{{Boundary Labeling in a Circular Orbit}},
  booktitle =	{32nd International Symposium on Graph Drawing and Network Visualization (GD 2024)},
  pages =	{22:1--22:17},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-343-0},
  ISSN =	{1868-8969},
  year =	{2024},
  volume =	{320},
  editor =	{Felsner, Stefan and Klein, Karsten},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.GD.2024.22},
  URN =		{urn:nbn:de:0030-drops-213060},
  doi =		{10.4230/LIPIcs.GD.2024.22},
  annote =	{Keywords: External labeling, Orthoradial drawing, NP-hardness, Polynomial algorithms}
}
Document
DOI: 10.4230/LIPIcs.GD.2024.31
Revisiting ILP Models for Exact Crossing Minimization in Storyline Drawings

Authors: Alexander Dobler, Michael Jünger, Paul J. Jünger, Julian Meffert, Petra Mutzel, and Martin Nöllenburg

Published in: LIPIcs, Volume 320, 32nd International Symposium on Graph Drawing and Network Visualization (GD 2024)

Abstract
Storyline drawings are a popular visualization of interactions of a set of characters over time, e.g., to show participants of scenes in a book or movie. Characters are represented as x-monotone curves that converge vertically for interactions and diverge otherwise. Combinatorially, the task of computing storyline drawings reduces to finding a sequence of permutations of the character curves for the different time points, with the primary objective being crossing minimization of the induced character trajectories. In this paper, we revisit exact integer linear programming (ILP) approaches for this NP-hard problem. By enriching previous formulations with additional problem-specific insights and new heuristics, we obtain exact solutions for an extended new benchmark set of larger and more complex instances than had been used before. Our experiments show that our enriched formulations lead to better performing algorithms when compared to state-of-the–art modelling techniques. In particular, our best algorithms are on average 2.6-3.2 times faster than the state-of-the-art and succeed in solving complex instances that could not be solved before within the given time limit. Further, we show in an ablation study that our enrichment components contribute considerably to the performance of the new ILP formulation.
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Alexander Dobler, Michael Jünger, Paul J. Jünger, Julian Meffert, Petra Mutzel, and Martin Nöllenburg. Revisiting ILP Models for Exact Crossing Minimization in Storyline Drawings. In 32nd International Symposium on Graph Drawing and Network Visualization (GD 2024). Leibniz International Proceedings in Informatics (LIPIcs), Volume 320, pp. 31:1-31:19, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2024)

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@InProceedings{dobler_et_al:LIPIcs.GD.2024.31,
  author =	{Dobler, Alexander and J\"{u}nger, Michael and J\"{u}nger, Paul J. and Meffert, Julian and Mutzel, Petra and N\"{o}llenburg, Martin},
  title =	{{Revisiting ILP Models for Exact Crossing Minimization in Storyline Drawings}},
  booktitle =	{32nd International Symposium on Graph Drawing and Network Visualization (GD 2024)},
  pages =	{31:1--31:19},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-343-0},
  ISSN =	{1868-8969},
  year =	{2024},
  volume =	{320},
  editor =	{Felsner, Stefan and Klein, Karsten},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.GD.2024.31},
  URN =		{urn:nbn:de:0030-drops-213159},
  doi =		{10.4230/LIPIcs.GD.2024.31},
  annote =	{Keywords: Storyline drawing, crossing minimization, integer linear programming, algorithm engineering, computational experiments}
}
Document
Poster Abstract
DOI: 10.4230/LIPIcs.GD.2024.43
Minimizing Switches in Cased Graph Drawings (Poster Abstract)

Authors: Robert Ganian, Martin Nöllenburg, and Sebastian Röder

Published in: LIPIcs, Volume 320, 32nd International Symposium on Graph Drawing and Network Visualization (GD 2024)

Abstract
In cased drawings of graphs, edges are drawn in front of others in order to decrease the negative impact of crossings on readability. In this context, a switch on an edge is defined as two consecutive crossings, where the edge is drawn in the front at one crossing and behind another edge at the next crossing. We investigate the problem of minimizing the maximum number of switches on any edge - both in a fixed drawing as well as for non-embedded graphs. We resolve an open question by Eppstein, van Kreveld, Mumford, and Speckmann (2009) by establishing the NP-hardness of minimizing the number of switches in a fixed drawing, provide a fixed-parameter algorithm for this problem, and obtain a full characterization of the problem for non-embedded graphs.
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Robert Ganian, Martin Nöllenburg, and Sebastian Röder. Minimizing Switches in Cased Graph Drawings (Poster Abstract). In 32nd International Symposium on Graph Drawing and Network Visualization (GD 2024). Leibniz International Proceedings in Informatics (LIPIcs), Volume 320, pp. 43:1-43:3, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2024)

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@InProceedings{ganian_et_al:LIPIcs.GD.2024.43,
  author =	{Ganian, Robert and N\"{o}llenburg, Martin and R\"{o}der, Sebastian},
  title =	{{Minimizing Switches in Cased Graph Drawings}},
  booktitle =	{32nd International Symposium on Graph Drawing and Network Visualization (GD 2024)},
  pages =	{43:1--43:3},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-343-0},
  ISSN =	{1868-8969},
  year =	{2024},
  volume =	{320},
  editor =	{Felsner, Stefan and Klein, Karsten},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.GD.2024.43},
  URN =		{urn:nbn:de:0030-drops-213271},
  doi =		{10.4230/LIPIcs.GD.2024.43},
  annote =	{Keywords: beyond planarity, complexity theory, non-planar drawings, crossings}
}
Document
Poster Abstract
DOI: 10.4230/LIPIcs.GD.2024.45
GdMetriX - A NetworkX Extension For Graph Drawing Metrics (Poster Abstract)

Authors: Martin Nöllenburg, Sebastian Röder, and Markus Wallinger

Published in: LIPIcs, Volume 320, 32nd International Symposium on Graph Drawing and Network Visualization (GD 2024)

Abstract
networkX is a well-established Python library for network analysis. With gdMetriX, we aim to extend the functionality of networkX and provide common quality metrics used in the field of graph drawing, such as the number of crossings or the angular resolution. In addition, the package provides easy-to-use access to the graph datasets provided by the ’Graph Layout Benchmark Datasets’ project from the Northeastern University Visualization Lab.
Cite as

Martin Nöllenburg, Sebastian Röder, and Markus Wallinger. GdMetriX - A NetworkX Extension For Graph Drawing Metrics (Poster Abstract). In 32nd International Symposium on Graph Drawing and Network Visualization (GD 2024). Leibniz International Proceedings in Informatics (LIPIcs), Volume 320, pp. 45:1-45:3, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2024)

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@InProceedings{nollenburg_et_al:LIPIcs.GD.2024.45,
  author =	{N\"{o}llenburg, Martin and R\"{o}der, Sebastian and Wallinger, Markus},
  title =	{{GdMetriX - A NetworkX Extension For Graph Drawing Metrics}},
  booktitle =	{32nd International Symposium on Graph Drawing and Network Visualization (GD 2024)},
  pages =	{45:1--45:3},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-343-0},
  ISSN =	{1868-8969},
  year =	{2024},
  volume =	{320},
  editor =	{Felsner, Stefan and Klein, Karsten},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.GD.2024.45},
  URN =		{urn:nbn:de:0030-drops-213294},
  doi =		{10.4230/LIPIcs.GD.2024.45},
  annote =	{Keywords: Graph Drawing Metrics}
}
Document
Poster Abstract
DOI: 10.4230/LIPIcs.GD.2024.49
Introducing Fairness in Graph Visualization (Poster Abstract)

Authors: Seok-Hee Hong, Giuseppe Liotta, Fabrizio Montecchiani, Martin Nöllenburg, and Tommaso Piselli

Published in: LIPIcs, Volume 320, 32nd International Symposium on Graph Drawing and Network Visualization (GD 2024)

Abstract
Information visualization tools are an essential component of many data-driven decision-making systems that rely on human feedback. The aim of this paper is to propose a novel research direction focused on fair visualizations of graphs.
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Seok-Hee Hong, Giuseppe Liotta, Fabrizio Montecchiani, Martin Nöllenburg, and Tommaso Piselli. Introducing Fairness in Graph Visualization (Poster Abstract). In 32nd International Symposium on Graph Drawing and Network Visualization (GD 2024). Leibniz International Proceedings in Informatics (LIPIcs), Volume 320, pp. 49:1-49:3, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2024)

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@InProceedings{hong_et_al:LIPIcs.GD.2024.49,
  author =	{Hong, Seok-Hee and Liotta, Giuseppe and Montecchiani, Fabrizio and N\"{o}llenburg, Martin and Piselli, Tommaso},
  title =	{{Introducing Fairness in Graph Visualization}},
  booktitle =	{32nd International Symposium on Graph Drawing and Network Visualization (GD 2024)},
  pages =	{49:1--49:3},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-343-0},
  ISSN =	{1868-8969},
  year =	{2024},
  volume =	{320},
  editor =	{Felsner, Stefan and Klein, Karsten},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.GD.2024.49},
  URN =		{urn:nbn:de:0030-drops-213338},
  doi =		{10.4230/LIPIcs.GD.2024.49},
  annote =	{Keywords: Network visualization, Fairness, Stress minimization}
}
Document
DOI: 10.4230/LIPIcs.SoCG.2024.19
Fully Dynamic Maximum Independent Sets of Disks in Polylogarithmic Update Time

Authors: Sujoy Bhore, Martin Nöllenburg, Csaba D. Tóth, and Jules Wulms

Published in: LIPIcs, Volume 293, 40th International Symposium on Computational Geometry (SoCG 2024)

Abstract
A fundamental question is whether one can maintain a maximum independent set (MIS) in polylogarithmic update time for a dynamic collection of geometric objects in Euclidean space. For a set of intervals, it is known that no dynamic algorithm can maintain an exact MIS in sublinear update time. Therefore, the typical objective is to explore the trade-off between update time and solution size. Substantial efforts have been made in recent years to understand this question for various families of geometric objects, such as intervals, hypercubes, hyperrectangles, and fat objects. We present the first fully dynamic approximation algorithm for disks of arbitrary radii in the plane that maintains a constant-factor approximate MIS in polylogarithmic expected amortized update time. Moreover, for a fully dynamic set of n unit disks in the plane, we show that a 12-approximate MIS can be maintained with worst-case update time O(log n), and optimal output-sensitive reporting. This result generalizes to fat objects of comparable sizes in any fixed dimension d, where the approximation ratio depends on the dimension and the fatness parameter. Further, we note that, even for a dynamic set of disks of unit radius in the plane, it is impossible to maintain O(1+ε)-approximate MIS in truly sublinear update time, under standard complexity assumptions. Our results build on two recent technical tools: (i) The MIX algorithm by Cardinal et al. (ESA 2021) that can smoothly transition from one independent set to another; hence it suffices to maintain a family of independent sets where the largest one is an O(1)-approximate MIS. (ii) A dynamic nearest/farthest neighbor data structure for disks by Kaplan et al. (DCG 2020) and Liu (SICOMP 2022), which generalizes the dynamic convex hull data structure by Chan (JACM 2010), and quickly yields a "replacement" disk (if any) when a disk in one of our independent sets is deleted.
Cite as

Sujoy Bhore, Martin Nöllenburg, Csaba D. Tóth, and Jules Wulms. Fully Dynamic Maximum Independent Sets of Disks in Polylogarithmic Update Time. In 40th International Symposium on Computational Geometry (SoCG 2024). Leibniz International Proceedings in Informatics (LIPIcs), Volume 293, pp. 19:1-19:16, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2024)

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@InProceedings{bhore_et_al:LIPIcs.SoCG.2024.19,
  author =	{Bhore, Sujoy and N\"{o}llenburg, Martin and T\'{o}th, Csaba D. and Wulms, Jules},
  title =	{{Fully Dynamic Maximum Independent Sets of Disks in Polylogarithmic Update Time}},
  booktitle =	{40th International Symposium on Computational Geometry (SoCG 2024)},
  pages =	{19:1--19:16},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-316-4},
  ISSN =	{1868-8969},
  year =	{2024},
  volume =	{293},
  editor =	{Mulzer, Wolfgang and Phillips, Jeff M.},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.SoCG.2024.19},
  URN =		{urn:nbn:de:0030-drops-199649},
  doi =		{10.4230/LIPIcs.SoCG.2024.19},
  annote =	{Keywords: Dynamic algorithm, Independent set, Geometric intersection graph}
}
Document
DOI: 10.4230/DagRep.13.4.58
New Frontiers of Parameterized Complexity in Graph Drawing (Dagstuhl Seminar 23162)

Authors: Robert Ganian, Fabrizio Montecchiani, Martin Nöllenburg, Meirav Zehavi, and Liana Khazaliya

Published in: Dagstuhl Reports, Volume 13, Issue 4 (2023)

Abstract
This report documents the program and the outcomes of Dagstuhl Seminar 23162 "New Frontiers of Parameterized Complexity in Graph Drawing”. The seminar was held in-person from April 16 to April 21, 2023. It brought together 32 researchers from the Graph Drawing and the Parameterized Complexity research communities to discuss and explore new research frontiers on the interface between the two fields. The report collects the abstracts of talks and open problems presented in the seminar, as well as brief progress reports from the working groups.
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Robert Ganian, Fabrizio Montecchiani, Martin Nöllenburg, Meirav Zehavi, and Liana Khazaliya. New Frontiers of Parameterized Complexity in Graph Drawing (Dagstuhl Seminar 23162). In Dagstuhl Reports, Volume 13, Issue 4, pp. 58-97, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2023)

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@Article{ganian_et_al:DagRep.13.4.58,
  author =	{Ganian, Robert and Montecchiani, Fabrizio and N\"{o}llenburg, Martin and Zehavi, Meirav and Khazaliya, Liana},
  title =	{{New Frontiers of Parameterized Complexity in Graph Drawing (Dagstuhl Seminar 23162)}},
  pages =	{58--97},
  journal =	{Dagstuhl Reports},
  ISSN =	{2192-5283},
  year =	{2023},
  volume =	{13},
  number =	{4},
  editor =	{Ganian, Robert and Montecchiani, Fabrizio and N\"{o}llenburg, Martin and Zehavi, Meirav and Khazaliya, Liana},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/DagRep.13.4.58},
  URN =		{urn:nbn:de:0030-drops-192393},
  doi =		{10.4230/DagRep.13.4.58},
  annote =	{Keywords: algorithm design, computational geometry, graph drawing, parameterized complexity}
}
Document
DOI: 10.4230/LIPIcs.GIScience.2023.2
Transitions in Dynamic Point Labeling

Authors: Thomas Depian, Guangping Li, Martin Nöllenburg, and Jules Wulms

Published in: LIPIcs, Volume 277, 12th International Conference on Geographic Information Science (GIScience 2023)

Abstract
The labeling of point features on a map is a well-studied topic. In a static setting, the goal is to find a non-overlapping label placement for (a subset of) point features. In a dynamic setting, the set of point features and their corresponding labels change, and the labeling has to adapt to such changes. To aid the user in tracking these changes, we can use morphs, here called transitions, to indicate how a labeling changes. Such transitions have not gained much attention yet, and we investigate different types of transitions for labelings of points, most notably consecutive transitions and simultaneous transitions. We give (tight) bounds on the number of overlaps that can occur during these transitions. When each label has a (non-negative) weight associated to it, and each overlap imposes a penalty proportional to the weight of the overlapping labels, we show that it is NP-complete to decide whether the penalty during a simultaneous transition has weight at most k. Finally, in a case study, we consider geotagged Twitter data on a map, by labeling points with rectangular labels showing tweets. We developed a prototype implementation to evaluate different transition styles in practice, measuring both number of overlaps and transition duration.
Cite as

Thomas Depian, Guangping Li, Martin Nöllenburg, and Jules Wulms. Transitions in Dynamic Point Labeling. In 12th International Conference on Geographic Information Science (GIScience 2023). Leibniz International Proceedings in Informatics (LIPIcs), Volume 277, pp. 2:1-2:19, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2023)

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@InProceedings{depian_et_al:LIPIcs.GIScience.2023.2,
  author =	{Depian, Thomas and Li, Guangping and N\"{o}llenburg, Martin and Wulms, Jules},
  title =	{{Transitions in Dynamic Point Labeling}},
  booktitle =	{12th International Conference on Geographic Information Science (GIScience 2023)},
  pages =	{2:1--2:19},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-288-4},
  ISSN =	{1868-8969},
  year =	{2023},
  volume =	{277},
  editor =	{Beecham, Roger and Long, Jed A. and Smith, Dianna and Zhao, Qunshan and Wise, Sarah},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.GIScience.2023.2},
  URN =		{urn:nbn:de:0030-drops-188971},
  doi =		{10.4230/LIPIcs.GIScience.2023.2},
  annote =	{Keywords: Dynamic labels, Label overlaps, Morphs, NP-completeness, Case study}
}
Document
DOI: 10.4230/LIPIcs.SoCG.2023.18
Extending Orthogonal Planar Graph Drawings Is Fixed-Parameter Tractable

Authors: Sujoy Bhore, Robert Ganian, Liana Khazaliya, Fabrizio Montecchiani, and Martin Nöllenburg

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

Abstract
The task of finding an extension to a given partial drawing of a graph while adhering to constraints on the representation has been extensively studied in the literature, with well-known results providing efficient algorithms for fundamental representations such as planar and beyond-planar topological drawings. In this paper, we consider the extension problem for bend-minimal orthogonal drawings of planar graphs, which is among the most fundamental geometric graph drawing representations. While the problem was known to be NP-hard, it is natural to consider the case where only a small part of the graph is still to be drawn. Here, we establish the fixed-parameter tractability of the problem when parameterized by the size of the missing subgraph. Our algorithm is based on multiple novel ingredients which intertwine geometric and combinatorial arguments. These include the identification of a new graph representation of bend-equivalent regions for vertex placement in the plane, establishing a bound on the treewidth of this auxiliary graph, and a global point-grid that allows us to discretize the possible placement of bends and vertices into locally bounded subgrids for each of the above regions.
Cite as

Sujoy Bhore, Robert Ganian, Liana Khazaliya, Fabrizio Montecchiani, and Martin Nöllenburg. Extending Orthogonal Planar Graph Drawings Is Fixed-Parameter Tractable. In 39th International Symposium on Computational Geometry (SoCG 2023). Leibniz International Proceedings in Informatics (LIPIcs), Volume 258, pp. 18:1-18:16, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2023)

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@InProceedings{bhore_et_al:LIPIcs.SoCG.2023.18,
  author =	{Bhore, Sujoy and Ganian, Robert and Khazaliya, Liana and Montecchiani, Fabrizio and N\"{o}llenburg, Martin},
  title =	{{Extending Orthogonal Planar Graph Drawings Is Fixed-Parameter Tractable}},
  booktitle =	{39th International Symposium on Computational Geometry (SoCG 2023)},
  pages =	{18:1--18:16},
  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.dagstuhl.de/entities/document/10.4230/LIPIcs.SoCG.2023.18},
  URN =		{urn:nbn:de:0030-drops-178689},
  doi =		{10.4230/LIPIcs.SoCG.2023.18},
  annote =	{Keywords: orthogonal drawings, bend minimization, extension problems, parameterized complexity}
}
Document
DOI: 10.4230/LIPIcs.ISAAC.2022.34
Minimum Link Fencing

Authors: Sujoy Bhore, Fabian Klute, Maarten Löffler, Martin Nöllenburg, Soeren Terziadis, and Anaïs Villedieu

Published in: LIPIcs, Volume 248, 33rd International Symposium on Algorithms and Computation (ISAAC 2022)

Abstract
We study a variant of the geometric multicut problem, where we are given a set 𝒫 of colored and pairwise interior-disjoint polygons in the plane. The objective is to compute a set of simple closed polygon boundaries (fences) that separate the polygons in such a way that any two polygons that are enclosed by the same fence have the same color, and the total number of links of all fences is minimized. We call this the minimum link fencing (MLF) problem and consider the natural case of bounded minimum link fencing (BMLF), where 𝒫 contains a polygon Q that is unbounded in all directions and can be seen as an outer polygon. We show that BMLF is NP-hard in general and that it is XP-time solvable when each fence contains at most two polygons and the number of segments per fence is the parameter. Finally, we present an O(n log n)-time algorithm for the case that the convex hull of 𝒫⧵{Q} does not intersect Q.
Cite as

Sujoy Bhore, Fabian Klute, Maarten Löffler, Martin Nöllenburg, Soeren Terziadis, and Anaïs Villedieu. Minimum Link Fencing. In 33rd International Symposium on Algorithms and Computation (ISAAC 2022). Leibniz International Proceedings in Informatics (LIPIcs), Volume 248, pp. 34:1-34:14, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2022)

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@InProceedings{bhore_et_al:LIPIcs.ISAAC.2022.34,
  author =	{Bhore, Sujoy and Klute, Fabian and L\"{o}ffler, Maarten and N\"{o}llenburg, Martin and Terziadis, Soeren and Villedieu, Ana\"{i}s},
  title =	{{Minimum Link Fencing}},
  booktitle =	{33rd International Symposium on Algorithms and Computation (ISAAC 2022)},
  pages =	{34:1--34:14},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-258-7},
  ISSN =	{1868-8969},
  year =	{2022},
  volume =	{248},
  editor =	{Bae, Sang Won and Park, Heejin},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.ISAAC.2022.34},
  URN =		{urn:nbn:de:0030-drops-173191},
  doi =		{10.4230/LIPIcs.ISAAC.2022.34},
  annote =	{Keywords: computational geometry, polygon nesting, polygon separation}
}
Document
DOI: 10.4230/DagRep.11.6.82
Parameterized Complexity in Graph Drawing (Dagstuhl Seminar 21293)

Authors: Robert Ganian, Fabrizio Montecchiani, Martin Nöllenburg, and Meirav Zehavi

Published in: Dagstuhl Reports, Volume 11, Issue 6 (2021)

Abstract
This report documents the program and the outcomes of Dagstuhl Seminar 21293 "Parameterized Complexity in Graph Drawing". The seminar was held mostly in-person from July 18 to July 23, 2021. It brought together 28 researchers from the Graph Drawing and the Parameterized Complexity research communities with the aim to discuss and explore open research questions on the interface between the two fields. The report collects the abstracts of talks and open problems presented in the seminar, as well as brief progress reports from the working groups.
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Robert Ganian, Fabrizio Montecchiani, Martin Nöllenburg, and Meirav Zehavi. Parameterized Complexity in Graph Drawing (Dagstuhl Seminar 21293). In Dagstuhl Reports, Volume 11, Issue 6, pp. 82-123, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2021)

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@Article{ganian_et_al:DagRep.11.6.82,
  author =	{Ganian, Robert and Montecchiani, Fabrizio and N\"{o}llenburg, Martin and Zehavi, Meirav},
  title =	{{Parameterized Complexity in Graph Drawing (Dagstuhl Seminar 21293)}},
  pages =	{82--123},
  journal =	{Dagstuhl Reports},
  ISSN =	{2192-5283},
  year =	{2021},
  volume =	{11},
  number =	{6},
  editor =	{Ganian, Robert and Montecchiani, Fabrizio and N\"{o}llenburg, Martin and Zehavi, Meirav},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/DagRep.11.6.82},
  URN =		{urn:nbn:de:0030-drops-155817},
  doi =		{10.4230/DagRep.11.6.82},
  annote =	{Keywords: exact computation, graph algorithms, graph drawing, parameterized complexity}
}
Document
DOI: 10.4230/LIPIcs.ISAAC.2021.19
Untangling Circular Drawings: Algorithms and Complexity

Authors: Sujoy Bhore, Guangping Li, Martin Nöllenburg, Ignaz Rutter, and Hsiang-Yun Wu

Published in: LIPIcs, Volume 212, 32nd International Symposium on Algorithms and Computation (ISAAC 2021)

Abstract
We consider the problem of untangling a given (non-planar) straight-line circular drawing δ_G of an outerplanar graph G = (V,E) into a planar straight-line circular drawing by shifting a minimum number of vertices to a new position on the circle. For an outerplanar graph G, it is clear that such a crossing-free circular drawing always exists and we define the circular shifting number shift°(δ_G) as the minimum number of vertices that need to be shifted to resolve all crossings of δ_G. We show that the problem Circular Untangling, asking whether shift°(δ_G) ≤ K for a given integer K, is NP-complete. Based on this result we study Circular Untangling for almost-planar circular drawings, in which a single edge is involved in all the crossings. In this case we provide a tight upper bound shift°(δ_G) ≤ ⌊n/2⌋-1, where n is the number of vertices in G, and present a polynomial-time algorithm to compute the circular shifting number of almost-planar drawings.
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Sujoy Bhore, Guangping Li, Martin Nöllenburg, Ignaz Rutter, and Hsiang-Yun Wu. Untangling Circular Drawings: Algorithms and Complexity. In 32nd International Symposium on Algorithms and Computation (ISAAC 2021). Leibniz International Proceedings in Informatics (LIPIcs), Volume 212, pp. 19:1-19:17, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2021)

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@InProceedings{bhore_et_al:LIPIcs.ISAAC.2021.19,
  author =	{Bhore, Sujoy and Li, Guangping and N\"{o}llenburg, Martin and Rutter, Ignaz and Wu, Hsiang-Yun},
  title =	{{Untangling Circular Drawings: Algorithms and Complexity}},
  booktitle =	{32nd International Symposium on Algorithms and Computation (ISAAC 2021)},
  pages =	{19:1--19:17},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-214-3},
  ISSN =	{1868-8969},
  year =	{2021},
  volume =	{212},
  editor =	{Ahn, Hee-Kap and Sadakane, Kunihiko},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.ISAAC.2021.19},
  URN =		{urn:nbn:de:0030-drops-154528},
  doi =		{10.4230/LIPIcs.ISAAC.2021.19},
  annote =	{Keywords: graph drawing, straight-line drawing, outerplanarity, NP-hardness, untangling}
}
Document
DOI: 10.4230/LIPIcs.ESA.2020.19
An Algorithmic Study of Fully Dynamic Independent Sets for Map Labeling

Authors: Sujoy Bhore, Guangping Li, and Martin Nöllenburg

Published in: LIPIcs, Volume 173, 28th Annual European Symposium on Algorithms (ESA 2020)

Abstract
Map labeling is a classical problem in cartography and geographic information systems (GIS) that asks to place labels for area, line, and point features, with the goal to select and place the maximum number of independent, i.e., overlap-free, labels. A practically interesting case is point labeling with axis-parallel rectangular labels of common size. In a fully dynamic setting, at each time step, either a new label appears or an existing label disappears. Then, the challenge is to maintain a maximum cardinality subset of pairwise independent labels with sub-linear update time. Motivated by this, we study the maximal independent set (MIS) and maximum independent set (Max-IS) problems on fully dynamic (insertion/deletion model) sets of axis-parallel rectangles of two types - (i) uniform height and width and (ii) uniform height and arbitrary width; both settings can be modeled as rectangle intersection graphs. We present the first deterministic algorithm for maintaining a MIS (and thus a 4-approximate Max-IS) of a dynamic set of uniform rectangles with amortized sub-logarithmic update time. This breaks the natural barrier of Ω(Δ) update time (where Δ is the maximum degree in the graph) for vertex updates presented by Assadi et al. (STOC 2018). We continue by investigating Max-IS and provide a series of deterministic dynamic approximation schemes. For uniform rectangles, we first give an algorithm that maintains a 4-approximate Max-IS with O(1) update time. In a subsequent algorithm, we establish the trade-off between approximation quality 2(1+1/k) and update time O(k²log n), for k ∈ ℕ. We conclude with an algorithm that maintains a 2-approximate Max-IS for dynamic sets of unit-height and arbitrary-width rectangles with O(ω log n) update time, where ω is the maximum size of an independent set of rectangles stabbed by any horizontal line. We have implemented our algorithms and report the results of an experimental comparison exploring the trade-off between solution quality and update time for synthetic and real-world map labeling instances.
Cite as

Sujoy Bhore, Guangping Li, and Martin Nöllenburg. An Algorithmic Study of Fully Dynamic Independent Sets for Map Labeling. In 28th Annual European Symposium on Algorithms (ESA 2020). Leibniz International Proceedings in Informatics (LIPIcs), Volume 173, pp. 19:1-19:24, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2020)

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@InProceedings{bhore_et_al:LIPIcs.ESA.2020.19,
  author =	{Bhore, Sujoy and Li, Guangping and N\"{o}llenburg, Martin},
  title =	{{An Algorithmic Study of Fully Dynamic Independent Sets for Map Labeling}},
  booktitle =	{28th Annual European Symposium on Algorithms (ESA 2020)},
  pages =	{19:1--19:24},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-162-7},
  ISSN =	{1868-8969},
  year =	{2020},
  volume =	{173},
  editor =	{Grandoni, Fabrizio and Herman, Grzegorz and Sanders, Peter},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.ESA.2020.19},
  URN =		{urn:nbn:de:0030-drops-128856},
  doi =		{10.4230/LIPIcs.ESA.2020.19},
  annote =	{Keywords: Independent Sets, Dynamic Algorithms, Rectangle Intersection Graphs, Approximation Algorithms, Experimental Evaluation}
}
Document
DOI: 10.4230/LIPIcs.MFCS.2020.14
Layered Fan-Planar Graph Drawings

Authors: Therese Biedl, Steven Chaplick, Michael Kaufmann, Fabrizio Montecchiani, Martin Nöllenburg, and Chrysanthi Raftopoulou

Published in: LIPIcs, Volume 170, 45th International Symposium on Mathematical Foundations of Computer Science (MFCS 2020)

Abstract
In a fan-planar drawing of a graph an edge can cross only edges with a common end-vertex. In this paper, we study fan-planar drawings that use h (horizontal) layers and are proper, i.e., edges connect adjacent layers. We show that if the embedding of the graph is fixed, then testing the existence of such drawings is fixed-parameter tractable in h, via a reduction to a similar result for planar graphs by Dujmović et al. If the embedding is not fixed, then we give partial results for h = 2: It was already known how to test the existence of fan-planar proper 2-layer drawings for 2-connected graphs, and we show here how to test this for trees. Along the way, we exhibit other interesting results for graphs with a fan-planar proper h-layer drawing; in particular we bound their pathwidth and show that they have a bar-1-visibility representation.
Cite as

Therese Biedl, Steven Chaplick, Michael Kaufmann, Fabrizio Montecchiani, Martin Nöllenburg, and Chrysanthi Raftopoulou. Layered Fan-Planar Graph Drawings. In 45th International Symposium on Mathematical Foundations of Computer Science (MFCS 2020). Leibniz International Proceedings in Informatics (LIPIcs), Volume 170, pp. 14:1-14:13, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2020)

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@InProceedings{biedl_et_al:LIPIcs.MFCS.2020.14,
  author =	{Biedl, Therese and Chaplick, Steven and Kaufmann, Michael and Montecchiani, Fabrizio and N\"{o}llenburg, Martin and Raftopoulou, Chrysanthi},
  title =	{{Layered Fan-Planar Graph Drawings}},
  booktitle =	{45th International Symposium on Mathematical Foundations of Computer Science (MFCS 2020)},
  pages =	{14:1--14:13},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-159-7},
  ISSN =	{1868-8969},
  year =	{2020},
  volume =	{170},
  editor =	{Esparza, Javier and Kr\'{a}l', Daniel},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.MFCS.2020.14},
  URN =		{urn:nbn:de:0030-drops-126835},
  doi =		{10.4230/LIPIcs.MFCS.2020.14},
  annote =	{Keywords: Graph Drawing, Parameterized Complexity, Beyond Planar Graphs}
}
Document
DOI: 10.4230/LIPIcs.MFCS.2020.31
Extending Nearly Complete 1-Planar Drawings in Polynomial Time

Authors: Eduard Eiben, Robert Ganian, Thekla Hamm, Fabian Klute, and Martin Nöllenburg

Published in: LIPIcs, Volume 170, 45th International Symposium on Mathematical Foundations of Computer Science (MFCS 2020)

Abstract
The problem of extending partial geometric graph representations such as plane graphs has received considerable attention in recent years. In particular, given a graph G, a connected subgraph H of G and a drawing H of H, the extension problem asks whether H can be extended into a drawing of G while maintaining some desired property of the drawing (e.g., planarity). In their breakthrough result, Angelini et al. [ACM TALG 2015] showed that the extension problem is polynomial-time solvable when the aim is to preserve planarity. Very recently we considered this problem for partial 1-planar drawings [ICALP 2020], which are drawings in the plane that allow each edge to have at most one crossing. The most important question identified and left open in that work is whether the problem can be solved in polynomial time when H can be obtained from G by deleting a bounded number of vertices and edges. In this work, we answer this question positively by providing a constructive polynomial-time decision algorithm.
Cite as

Eduard Eiben, Robert Ganian, Thekla Hamm, Fabian Klute, and Martin Nöllenburg. Extending Nearly Complete 1-Planar Drawings in Polynomial Time. In 45th International Symposium on Mathematical Foundations of Computer Science (MFCS 2020). Leibniz International Proceedings in Informatics (LIPIcs), Volume 170, pp. 31:1-31:16, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2020)

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@InProceedings{eiben_et_al:LIPIcs.MFCS.2020.31,
  author =	{Eiben, Eduard and Ganian, Robert and Hamm, Thekla and Klute, Fabian and N\"{o}llenburg, Martin},
  title =	{{Extending Nearly Complete 1-Planar Drawings in Polynomial Time}},
  booktitle =	{45th International Symposium on Mathematical Foundations of Computer Science (MFCS 2020)},
  pages =	{31:1--31:16},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-159-7},
  ISSN =	{1868-8969},
  year =	{2020},
  volume =	{170},
  editor =	{Esparza, Javier and Kr\'{a}l', Daniel},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.MFCS.2020.31},
  URN =		{urn:nbn:de:0030-drops-126998},
  doi =		{10.4230/LIPIcs.MFCS.2020.31},
  annote =	{Keywords: Extension problems, 1-planarity}
}
Document
Track A: Algorithms, Complexity and Games
DOI: 10.4230/LIPIcs.ICALP.2020.43
Extending Partial 1-Planar Drawings

Authors: Eduard Eiben, Robert Ganian, Thekla Hamm, Fabian Klute, and Martin Nöllenburg

Published in: LIPIcs, Volume 168, 47th International Colloquium on Automata, Languages, and Programming (ICALP 2020)

Abstract
Algorithmic extension problems of partial graph representations such as planar graph drawings or geometric intersection representations are of growing interest in topological graph theory and graph drawing. In such an extension problem, we are given a tuple (G,H,ℋ) consisting of a graph G, a connected subgraph H of G and a drawing ℋ of H, and the task is to extend ℋ into a drawing of G while maintaining some desired property of the drawing, such as planarity. In this paper we study the problem of extending partial 1-planar drawings, which are drawings in the plane that allow each edge to have at most one crossing. In addition we consider the subclass of IC-planar drawings, which are 1-planar drawings with independent crossings. Recognizing 1-planar graphs as well as IC-planar graphs is NP-complete and the NP-completeness easily carries over to the extension problem. Therefore, our focus lies on establishing the tractability of such extension problems in a weaker sense than polynomial-time tractability. Here, we show that both problems are fixed-parameter tractable when parameterized by the number of edges missing from H, i.e., the edge deletion distance between H and G. The second part of the paper then turns to a more powerful parameterization which is based on measuring the vertex+edge deletion distance between the partial and complete drawing, i.e., the minimum number of vertices and edges that need to be deleted to obtain H from G.
Cite as

Eduard Eiben, Robert Ganian, Thekla Hamm, Fabian Klute, and Martin Nöllenburg. Extending Partial 1-Planar Drawings. In 47th International Colloquium on Automata, Languages, and Programming (ICALP 2020). Leibniz International Proceedings in Informatics (LIPIcs), Volume 168, pp. 43:1-43:19, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2020)

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@InProceedings{eiben_et_al:LIPIcs.ICALP.2020.43,
  author =	{Eiben, Eduard and Ganian, Robert and Hamm, Thekla and Klute, Fabian and N\"{o}llenburg, Martin},
  title =	{{Extending Partial 1-Planar Drawings}},
  booktitle =	{47th International Colloquium on Automata, Languages, and Programming (ICALP 2020)},
  pages =	{43:1--43:19},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-138-2},
  ISSN =	{1868-8969},
  year =	{2020},
  volume =	{168},
  editor =	{Czumaj, Artur and Dawar, Anuj and Merelli, Emanuela},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.ICALP.2020.43},
  URN =		{urn:nbn:de:0030-drops-124509},
  doi =		{10.4230/LIPIcs.ICALP.2020.43},
  annote =	{Keywords: Extension problems, 1-planarity, parameterized algorithms}
}
Document
DOI: 10.4230/LIPIcs.SoCG.2018.53
Minimizing Crossings in Constrained Two-Sided Circular Graph Layouts

Authors: Fabian Klute and Martin Nöllenburg

Published in: LIPIcs, Volume 99, 34th International Symposium on Computational Geometry (SoCG 2018)

Abstract
Circular layouts are a popular graph drawing style, where vertices are placed on a circle and edges are drawn as straight chords. Crossing minimization in circular layouts is NP-hard. One way to allow for fewer crossings in practice are two-sided layouts that draw some edges as curves in the exterior of the circle. In fact, one- and two-sided circular layouts are equivalent to one-page and two-page book drawings, i.e., graph layouts with all vertices placed on a line (the spine) and edges drawn in one or two distinct half-planes (the pages) bounded by the spine. In this paper we study the problem of minimizing the crossings for a fixed cyclic vertex order by computing an optimal k-plane set of exteriorly drawn edges for k >= 1, extending the previously studied case k=0. We show that this relates to finding bounded-degree maximum-weight induced subgraphs of circle graphs, which is a graph-theoretic problem of independent interest. We show NP-hardness for arbitrary k, present an efficient algorithm for k=1, and generalize it to an explicit XP-time algorithm for any fixed k. For the practically interesting case k=1 we implemented our algorithm and present experimental results that confirm the applicability of our algorithm.
Cite as

Fabian Klute and Martin Nöllenburg. Minimizing Crossings in Constrained Two-Sided Circular Graph Layouts. In 34th International Symposium on Computational Geometry (SoCG 2018). Leibniz International Proceedings in Informatics (LIPIcs), Volume 99, pp. 53:1-53:14, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2018)

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@InProceedings{klute_et_al:LIPIcs.SoCG.2018.53,
  author =	{Klute, Fabian and N\"{o}llenburg, Martin},
  title =	{{Minimizing Crossings in Constrained Two-Sided Circular Graph Layouts}},
  booktitle =	{34th International Symposium on Computational Geometry (SoCG 2018)},
  pages =	{53:1--53:14},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-066-8},
  ISSN =	{1868-8969},
  year =	{2018},
  volume =	{99},
  editor =	{Speckmann, Bettina and T\'{o}th, Csaba D.},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.SoCG.2018.53},
  URN =		{urn:nbn:de:0030-drops-87663},
  doi =		{10.4230/LIPIcs.SoCG.2018.53},
  annote =	{Keywords: Graph Drawing, Circular Layouts, Crossing Minimization, Circle Graphs, Bounded-Degree Maximum-Weight Induced Subgraphs}
}
Document
DOI: 10.4230/DagRep.7.8.1
Scalable Set Visualizations (Dagstuhl Seminar 17332)

Authors: Yifan Hu, Luana Micallef, Martin Nöllenburg, and Peter Rodgers

Published in: Dagstuhl Reports, Volume 7, Issue 8 (2018)

Abstract
This report documents the program and outcomes of Dagstuhl Seminar 17332 "Scalable Set Visualizations", which took place August 14--18, 2017. The interdisciplinary seminar brought together 26 researchers from different areas in computer science and beyond such as information visualization, human-computer interaction, graph drawing, algorithms, machine learning, geography, and life sciences. During the seminar we had five invited overview talks on different aspects of set visualizations as well as a few ad-hoc presentations of ongoing work. The abstracts of these talks are contained in this report. Furthermore, we formed five working groups, each of them discussing intensively about a selected open research problem that was proposed by the seminar participants in an open problem session. The second part of this report contains summaries of the groups' findings.
Cite as

Yifan Hu, Luana Micallef, Martin Nöllenburg, and Peter Rodgers. Scalable Set Visualizations (Dagstuhl Seminar 17332). In Dagstuhl Reports, Volume 7, Issue 8, pp. 1-22, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2018)

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@Article{hu_et_al:DagRep.7.8.1,
  author =	{Hu, Yifan and Micallef, Luana and N\"{o}llenburg, Martin and Rodgers, Peter},
  title =	{{Scalable Set Visualizations (Dagstuhl Seminar 17332)}},
  pages =	{1--22},
  journal =	{Dagstuhl Reports},
  ISSN =	{2192-5283},
  year =	{2018},
  volume =	{7},
  number =	{8},
  editor =	{Hu, Yifan and Micallef, Luana and N\"{o}llenburg, Martin and Rodgers, Peter},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/DagRep.7.8.1},
  URN =		{urn:nbn:de:0030-drops-84274},
  doi =		{10.4230/DagRep.7.8.1},
  annote =	{Keywords: algorithms, information visualization, scalability, set visualization, visual analytics}
}
Document
DOI: 10.4230/OASIcs.ATMOS.2015.1
Towards Realistic Pedestrian Route Planning

Authors: Simeon Andreev, Julian Dibbelt, Martin Nöllenburg, Thomas Pajor, and Dorothea Wagner

Published in: OASIcs, Volume 48, 15th Workshop on Algorithmic Approaches for Transportation Modelling, Optimization, and Systems (ATMOS 2015)

Abstract
Pedestrian routing has its specific set of challenges, which are often neglected by state-of-the-art route planners. For instance, the lack of detailed sidewalk data and the inability to traverse plazas and parks in a natural way often leads to unappealing and suboptimal routes. In this work, we first propose to augment the network by generating sidewalks based on the street geometry and adding edges for routing over plazas and squares. Using this and further information, our query algorithm seamlessly handles node-to-node queries and queries whose origin or destination is an arbitrary location on a plaza or inside a park. Our experiments show that we are able to compute appealing pedestrian routes at negligible overhead over standard routing algorithms.
Cite as

Simeon Andreev, Julian Dibbelt, Martin Nöllenburg, Thomas Pajor, and Dorothea Wagner. Towards Realistic Pedestrian Route Planning. In 15th Workshop on Algorithmic Approaches for Transportation Modelling, Optimization, and Systems (ATMOS 2015). Open Access Series in Informatics (OASIcs), Volume 48, pp. 1-15, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2015)

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@InProceedings{andreev_et_al:OASIcs.ATMOS.2015.1,
  author =	{Andreev, Simeon and Dibbelt, Julian and N\"{o}llenburg, Martin and Pajor, Thomas and Wagner, Dorothea},
  title =	{{Towards Realistic Pedestrian Route Planning}},
  booktitle =	{15th Workshop on Algorithmic Approaches for Transportation Modelling, Optimization, and Systems (ATMOS 2015)},
  pages =	{1--15},
  series =	{Open Access Series in Informatics (OASIcs)},
  ISBN =	{978-3-939897-99-6},
  ISSN =	{2190-6807},
  year =	{2015},
  volume =	{48},
  editor =	{Italiano, Giuseppe F. and Schmidt, Marie},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/OASIcs.ATMOS.2015.1},
  URN =		{urn:nbn:de:0030-drops-54592},
  doi =		{10.4230/OASIcs.ATMOS.2015.1},
  annote =	{Keywords: pedestrian routing, realistic model, shortest paths, speed-up technique}
}
Document
DOI: 10.4230/DagRep.5.1.243
Empirical Evaluation for Graph Drawing (Dagstuhl Seminar 15052)

Authors: Ulrik Brandes, Irene Finocchi, Martin Nöllenburg, and Aaron Quigley

Published in: Dagstuhl Reports, Volume 5, Issue 1 (2015)

Abstract
This report documents the program and outcomes of Dagstuhl Seminar 15052 "Empirical Evaluation for Graph Drawing" which took place January 25-30, 2015. The goal of the seminar was to advance the state of the art in experimental evaluation within the wider field of graph drawing, both with respect to user studies and algorithmic experimentation.
Cite as

Ulrik Brandes, Irene Finocchi, Martin Nöllenburg, and Aaron Quigley. Empirical Evaluation for Graph Drawing (Dagstuhl Seminar 15052). In Dagstuhl Reports, Volume 5, Issue 1, pp. 243-258, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2015)

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@Article{brandes_et_al:DagRep.5.1.243,
  author =	{Brandes, Ulrik and Finocchi, Irene and N\"{o}llenburg, Martin and Quigley, Aaron},
  title =	{{Empirical Evaluation for Graph Drawing (Dagstuhl Seminar 15052)}},
  pages =	{243--258},
  journal =	{Dagstuhl Reports},
  ISSN =	{2192-5283},
  year =	{2015},
  volume =	{5},
  number =	{1},
  editor =	{Brandes, Ulrik and Finocchi, Irene and N\"{o}llenburg, Martin and Quigley, Aaron},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/DagRep.5.1.243},
  URN =		{urn:nbn:de:0030-drops-50414},
  doi =		{10.4230/DagRep.5.1.243},
  annote =	{Keywords: graph drawing, experimental design, algorithm engineering, user studies, empirical evaluation, information visualization}
}
Document
DOI: 10.4230/DagRep.3.4.34
Drawing Graphs and Maps with Curves (Dagstuhl Seminar 13151)

Authors: Stephen G. Kobourov, Martin Nöllenburg, and Monique Teillaud

Published in: Dagstuhl Reports, Volume 3, Issue 4 (2013)

Abstract
This report documents the program and the outcomes of Dagstuhl Seminar 13151 "Drawing Graphs and Maps with Curves". The seminar brought together 34 researchers from different areas such as graph drawing, information visualization, computational geometry, and cartography. During the seminar we started with seven overview talks on the use of curves in the different communities represented in the seminar. Abstracts of these talks are collected in this report. Six working groups formed around open research problems related to the seminar topic and we report about their findings. Finally, the seminar was accompanied by the art exhibition Bending Reality: Where Arc and Science Meet with 40 exhibits contributed by the seminar participants.
Cite as

Stephen G. Kobourov, Martin Nöllenburg, and Monique Teillaud. Drawing Graphs and Maps with Curves (Dagstuhl Seminar 13151). In Dagstuhl Reports, Volume 3, Issue 4, pp. 34-68, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2013)

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@Article{kobourov_et_al:DagRep.3.4.34,
  author =	{Kobourov, Stephen G. and N\"{o}llenburg, Martin and Teillaud, Monique},
  title =	{{Drawing Graphs and Maps with Curves (Dagstuhl Seminar 13151)}},
  pages =	{34--68},
  journal =	{Dagstuhl Reports},
  ISSN =	{2192-5283},
  year =	{2013},
  volume =	{3},
  number =	{4},
  editor =	{Kobourov, Stephen G. and N\"{o}llenburg, Martin and Teillaud, Monique},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/DagRep.3.4.34},
  URN =		{urn:nbn:de:0030-drops-41680},
  doi =		{10.4230/DagRep.3.4.34},
  annote =	{Keywords: graph drawing, information visualization, computational cartography, computational geometry}
}
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