15 Search Results for "H�sel, Matthias"

Document
DOI: 10.4230/LIPIcs.STACS.2024.48
FPT Approximation of Generalised Hypertree Width for Bounded Intersection Hypergraphs

Authors: Matthias Lanzinger and Igor Razgon

Published in: LIPIcs, Volume 289, 41st International Symposium on Theoretical Aspects of Computer Science (STACS 2024)

Abstract
Generalised hypertree width (ghw) is a hypergraph parameter that is central to the tractability of many prominent problems with natural hypergraph structure. Computing ghw of a hypergraph is notoriously hard. The decision version of the problem, checking whether ghw(H) ≤ k, is paraNP-hard when parameterised by k. Furthermore, approximation of ghw is at least as hard as approximation of Set-Cover, which is known to not admit any FPT approximation algorithms. Research in the computation of ghw so far has focused on identifying structural restrictions to hypergraphs - such as bounds on the size of edge intersections - that permit XP algorithms for ghw. Yet, even under these restrictions that problem has so far evaded any kind of FPT algorithm. In this paper we make the first step towards FPT algorithms for ghw by showing that the parameter can be approximated in FPT time for graphs of bounded edge intersection size. In concrete terms we show that there exists an FPT algorithm, parameterised by k and d, that for input hypergraph H with maximal cardinality of edge intersections d and integer k either outputs a tree decomposition with ghw(H) ≤ 4k(k+d+1)(2k-1), or rejects, in which case it is guaranteed that ghw(H) > k. Thus, in the special case of hypergraphs of bounded edge intersection, we obtain an FPT O(k³)-approximation algorithm for ghw.
Cite as

Matthias Lanzinger and Igor Razgon. FPT Approximation of Generalised Hypertree Width for Bounded Intersection Hypergraphs. In 41st International Symposium on Theoretical Aspects of Computer Science (STACS 2024). Leibniz International Proceedings in Informatics (LIPIcs), Volume 289, pp. 48:1-48:17, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2024)

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@InProceedings{lanzinger_et_al:LIPIcs.STACS.2024.48,
  author =	{Lanzinger, Matthias and Razgon, Igor},
  title =	{{FPT Approximation of Generalised Hypertree Width for Bounded Intersection Hypergraphs}},
  booktitle =	{41st International Symposium on Theoretical Aspects of Computer Science (STACS 2024)},
  pages =	{48:1--48:17},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-311-9},
  ISSN =	{1868-8969},
  year =	{2024},
  volume =	{289},
  editor =	{Beyersdorff, Olaf and Kant\'{e}, Mamadou Moustapha and Kupferman, Orna and Lokshtanov, Daniel},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.STACS.2024.48},
  URN =		{urn:nbn:de:0030-drops-197588},
  doi =		{10.4230/LIPIcs.STACS.2024.48},
  annote =	{Keywords: generalized hypertree width, hypergraphs, parameterized algorithms, approximation algorithms}
}
Document
Invited Talk
DOI: 10.4230/LIPIcs.CP.2023.1
Beyond Optimal Solutions for Real-World Problems (Invited Talk)

Authors: Maria Garcia de la Banda

Published in: LIPIcs, Volume 280, 29th International Conference on Principles and Practice of Constraint Programming (CP 2023)

Abstract
Combinatorial optimisation technology has come a long way. We now have mature high-level modelling languages in which to specify a model of the particular problem of interest [Nethercote et al., 2007; Frisch et al., 2008; Van Hentenryck, 1999; Fourer et al., 1990]; robust complete solvers in each major constraint paradigm, including Constraint Programming (CP), MaxSAT [Jessica Davies and Fahiem Bacchus, 2011; Alexey Ignatiev et al., 2019], and Mixed Integer Programming (MIP); effective incomplete search techniques that can easily be combined with complete solvers to speed up the search such as Large Neighbourhood Search [Paul Shaw, 1998]; and enough general knowledge about modelling techniques to understand the need for our models to incorporate components such as global constraints [Willem-Jan van Hoeve and Irit Katriel, 2006], symmetry constraints [Ian P. Gent et al., 2006], and more. All this has significantly reduced the amount of knowledge required to apply this technology successfully to the many different combinatorial optimisation problems that permeate our society. And yet, not many organisations use such advanced optimisation technology; instead, they often rely on the solutions provided by problem-specific algorithms that are implemented in traditional imperative languages and lack any of the above advances. Further, while advanced optimisation technology is particularly suitable for the kind of complex human-in-the-loop decision-making problems that occur in critical sectors of our society, including health, transport, energy, disaster management, environment and finance, these decisions are often still made by people with little or no technological support. In this extended abstract I argue that to change this state of affairs, our research focus needs to change from improving the technology on its own, to improving it so that users can better trust, use, and maintain the optimisation systems that we develop with it. The rest of this extended abstract discusses my personal experiences and opinion on these three points. Trust I highlight trust (which focuses on the user’s point of view) rather than trustworthiness (which is a characteristic of the software itself) because I think it is the former rather than the latter that is at stake for the adoption of optimisation technology. One of the biggest hurdles I have found for trust in the context of optimisation systems is for the domain experts to (feel like they) understand the underlying model. While many users will never do (or have to), I believe it is key for domain experts to have a high-level understanding of the constraints in the model, since their (dis)trust will likely spread through the organisation, impacting the adoption of the system. Thanks to the use of high-level modelling languages in CP, our group has achieved this [Matthias Klapperstueck et al., 2023] by documenting the constraints in a language the user knows (mathematics) and linking each constraint to the particular part of the model that implements it (via comments). While domain experts do not completely understand the model, the similarity between the format they understand (mathematics) and the model constraint has helped them verify our perception of their problem and improved their trust in the model. However, more needs to be done in this direction via the development of formal techniques. For example, our group is exploring the use of domain-specific languages [Hudak, 1997] as a bridge between domain experts and modellers that helps both trust and maintenance (see later). This [Sameela Suharshani Wijesundara et al., 2023] and other approaches need to be explored. A very significant source of trust for our domain experts (and of trustworthiness for the software) has been the development of two different models implemented by two different people for the same problem [Matthias Klapperstueck et al., 2023]. While this can be seen as a prohibitively expensive exercise, it did not take that long once the first model was mature, is a good way to onboard new optimisation team members, and has helped up detect not only bugs but also differences in the interpretation of domain expert information. For optimisation problems where it is not possible to verify the optimality (or even correctness) of the solution, we see such redundant modelling as the only solution for now. Interestingly, a significant step forward in obtaining the trust of our domain experts has been the generation of an optimality gap whenever an optimal solution could not be found due to time constraints. While explaining this concept took time, once understood it has boosted their trust, particularly when tackling problems where the solution is not easy verifiable or when approximated models/data are used (needed for speed, see later). This makes it difficult to work with CP and SAT solvers, as they usually lack tight lower bounds. Finally, trust is often developed through the use of the system, which I discuss below. Use Usability is known to be key for the deployment of software systems. By "system" in our context, I refer to the combination of the problem model(s), the associated solver(s) and, importantly, the User Interface (UI) that often integrates them and is fundamental to their success. In addition to the traditional usability characteristics of software systems, I believe an optimisation system requires particular care in the following areas. Interaction, i.e., the system must allow users to interact with the UI not only to provide and modify the input data, but also to modify the constraints (at the very least by turning some on/off) as well as explore and compare solutions, as argued in [David Meignan et al., 2015; Jie Liu et al., 2021]. Incremental compilers and solvers would significantly help in making this easier, as well as generic ways for the UIs to communicate with them. Conflict resolution, that is, ensuring the system can not only detect infeasible instances, but also support users in understanding the data/constraints that cause infeasibility and how to modify the instance to make it feasible. Any interactive optimisation system that has users, will likely have conflicts. Thus, it is mandatory for CP to improve its conflict resolution technology which, while existent [João Marques-Silva and Alessandro Previti, 2014; Lauffer and Topcu, 2019; Ilankaikone Senthooran et al., 2023], is not widespread and it is often still problem-dependent, overwhelming (in the number of constraints shown to the user) and slow. Without it, users will be "stumped" when (rather than if) infeasibility is reached. Solution diversity, that is, supporting users in obtaining a diverse set of (close-to-optimal) solutions, where diversity is measured by a user-provided metric modelled somehow. While some solver-independent technology has been developed and implemented for this [Emmanuel Hebrard et al., 2005; Thierry Petit and Andrew C. Trapp, 2015; Linnea Ingmar et al., 2020], it should be easier to use and more widespread. Further, it requires sophisticated solution comparison capabilities and, importantly, for optimal solutions to be found in seconds rather than hours. This brings me to speed, an area where CP solvers are falling behind. Most of our research group applications now use MIP solvers due to the need for floats (which precludes us from using learning solvers such as Chuffed [Geoffrey Chu, 2013]), but also to the lack of effective warm-start processes that are available in MIP solvers. Interestingly, data and model approximations have been proved to achieve orders of magnitude speedups with small reductions in optimality [Matthias Klapperstueck et al., 2023]. Developing generic (i.e., problem independent) accurate approximations would be extremely useful for complex decision systems. Other areas where I think generic CP methods are worth investigating more include dealing with uncertainty and online problems, ensuring solution fairness (even if it is over time), and studying predict + optimise approaches. Maintain I know very few papers devoted to the issue of maintenance in optimisation technology. While this may be due to my lack of knowledge, I suspect it is also due to the limited adoption of optimisation technology. While the issues in this area are again common to other software systems, I believe the solutions for CP require special attention. For example, the issue of changes in user requirements (that our research group calls problem drift) seems particularly prevalent in decision-making systems, as such problems can evolve rapidly due to unforeseen circumstances. This can make optimisation systems obsolete faster than expected. Our research group has proposed to tackle problem drift by developing a requirements model implemented in the above-mentioned MDSLs and created by both domain experts and modellers that, when modified re-generates parts of the model to support the modifications [Sameela Suharshani Wijesundara et al., 2023]. This and other approaches such as the creation of reusable models components [Sophia Saller and Jana Koehler, 2022; Toby Walsh, 2003], or instantiatable classes for common problem domains, are worth investigating.
Cite as

Maria Garcia de la Banda. Beyond Optimal Solutions for Real-World Problems (Invited Talk). In 29th International Conference on Principles and Practice of Constraint Programming (CP 2023). Leibniz International Proceedings in Informatics (LIPIcs), Volume 280, pp. 1:1-1:4, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2023)

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@InProceedings{garciadelabanda:LIPIcs.CP.2023.1,
  author =	{Garcia de la Banda, Maria},
  title =	{{Beyond Optimal Solutions for Real-World Problems}},
  booktitle =	{29th International Conference on Principles and Practice of Constraint Programming (CP 2023)},
  pages =	{1:1--1:4},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-300-3},
  ISSN =	{1868-8969},
  year =	{2023},
  volume =	{280},
  editor =	{Yap, Roland H. C.},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops-dev.dagstuhl.de/entities/document/10.4230/LIPIcs.CP.2023.1},
  URN =		{urn:nbn:de:0030-drops-190384},
  doi =		{10.4230/LIPIcs.CP.2023.1},
  annote =	{Keywords: Combinatorial optimisation systems, usability, trust, maintenance}
}
Document
DOI: 10.4230/LIPIcs.CP.2023.21
Exploring Hydrogen Supply/Demand Networks: Modeller and Domain Expert Views

Authors: Matthias Klapperstueck, Frits de Nijs, Ilankaikone Senthooran, Jack Lee-Kopij, Maria Garcia de la Banda, and Michael Wybrow

Published in: LIPIcs, Volume 280, 29th International Conference on Principles and Practice of Constraint Programming (CP 2023)

Abstract
Energy companies are considering producing renewable fuels such as hydrogen/ammonia. Setting up a production network means deciding where to build production plants, and how to operate them at minimum electricity and transport costs. These decisions are complicated by many factors including the difficulty in obtaining accurate current data (e.g., electricity price and transport costs) for potential supply locations, the accuracy of data predictions (e.g., for demand and costs), and the need for some decisions to be made due to external (not modelled) factors. Thus, decision-makers need access to a user-centric decision system that helps them visualise, explore, interact and compare the many possible solutions of many different scenarios. This paper describes the system we have built to support our energy partner in making such decisions, and shows the advantages of having a graphical user-focused interactive tool, and of using a high-level constraint modelling language (MiniZinc) to implement the underlying model.
Cite as

Matthias Klapperstueck, Frits de Nijs, Ilankaikone Senthooran, Jack Lee-Kopij, Maria Garcia de la Banda, and Michael Wybrow. Exploring Hydrogen Supply/Demand Networks: Modeller and Domain Expert Views. In 29th International Conference on Principles and Practice of Constraint Programming (CP 2023). Leibniz International Proceedings in Informatics (LIPIcs), Volume 280, pp. 21:1-21:18, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2023)

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@InProceedings{klapperstueck_et_al:LIPIcs.CP.2023.21,
  author =	{Klapperstueck, Matthias and de Nijs, Frits and Senthooran, Ilankaikone and Lee-Kopij, Jack and Garcia de la Banda, Maria and Wybrow, Michael},
  title =	{{Exploring Hydrogen Supply/Demand Networks: Modeller and Domain Expert Views}},
  booktitle =	{29th International Conference on Principles and Practice of Constraint Programming (CP 2023)},
  pages =	{21:1--21:18},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-300-3},
  ISSN =	{1868-8969},
  year =	{2023},
  volume =	{280},
  editor =	{Yap, Roland H. C.},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops-dev.dagstuhl.de/entities/document/10.4230/LIPIcs.CP.2023.21},
  URN =		{urn:nbn:de:0030-drops-190584},
  doi =		{10.4230/LIPIcs.CP.2023.21},
  annote =	{Keywords: Facility Location, Hydrogen Supply Chain, Human-Centric Optimisation}
}
Document
Short Paper
DOI: 10.4230/LIPIcs.GIScience.2023.63
Calculating Shadows with U-Nets for Urban Environments (Short Paper)

Authors: Dominik Rothschedl, Franz Welscher, Franziska Hübl, Ivan Majic, Daniele Giannandrea, Matthias Wastian, Johannes Scholz, and Niki Popper

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

Abstract
Shadow calculation is an important prerequisite for many urban and environmental analyses such as the assessment of solar energy potential. We propose a neural net approach that can be trained with 3D geographical information and predict the presence and depth of shadows. We adapt a U-Net algorithm traditionally used in biomedical image segmentation and train it on sections of Styria, Austria. Our two-step approach first predicts binary existence of shadows and then estimates the depth of shadows as well. Our results on the case study of Styria, Austria show that the proposed approach can predict in both models shadows with over 80% accuracy which is satisfactory for real-world applications, but still leaves room for improvement.
Cite as

Dominik Rothschedl, Franz Welscher, Franziska Hübl, Ivan Majic, Daniele Giannandrea, Matthias Wastian, Johannes Scholz, and Niki Popper. Calculating Shadows with U-Nets for Urban Environments (Short Paper). In 12th International Conference on Geographic Information Science (GIScience 2023). Leibniz International Proceedings in Informatics (LIPIcs), Volume 277, pp. 63:1-63:6, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2023)

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@InProceedings{rothschedl_et_al:LIPIcs.GIScience.2023.63,
  author =	{Rothschedl, Dominik and Welscher, Franz and H\"{u}bl, Franziska and Majic, Ivan and Giannandrea, Daniele and Wastian, Matthias and Scholz, Johannes and Popper, Niki},
  title =	{{Calculating Shadows with U-Nets for Urban Environments}},
  booktitle =	{12th International Conference on Geographic Information Science (GIScience 2023)},
  pages =	{63:1--63:6},
  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-dev.dagstuhl.de/entities/document/10.4230/LIPIcs.GIScience.2023.63},
  URN =		{urn:nbn:de:0030-drops-189581},
  doi =		{10.4230/LIPIcs.GIScience.2023.63},
  annote =	{Keywords: Neural Net, U-Net, Residual Net, Shadow Calculation}
}
Document
DOI: 10.4230/LIPIcs.STACS.2023.12
On the Multilinear Complexity of Associative Algebras

Authors: Markus Bläser, Hendrik Mayer, and Devansh Shringi

Published in: LIPIcs, Volume 254, 40th International Symposium on Theoretical Aspects of Computer Science (STACS 2023)

Abstract
Christandl and Zuiddam [Matthias Christandl and Jeroen Zuiddam, 2019] study the multilinear complexity of d-fold matrix multiplication in the context of quantum communication complexity. Bshouty [Nader H. Bshouty, 2013] investigates the multilinear complexity of d-fold multiplication in commutative algebras to understand the size of so-called testers. The study of bilinear complexity is a classical topic in algebraic complexity theory, starting with the work by Strassen. However, there has been no systematic study of the multilinear complexity of multilinear maps. In the present work, we systematically investigate the multilinear complexity of d-fold multiplication in arbitrary associative algebras. We prove a multilinear generalization of the famous Alder-Strassen theorem, which is a lower bound for the bilinear complexity of the (2-fold) multiplication in an associative algebra. We show that the multilinear complexity of the d-fold multiplication has a lower bound of d ⋅ dim A - (d-1)t, where t is the number of maximal twosided ideals in A. This is optimal in the sense that there are algebras for which this lower bound is tight. Furthermore, we prove the following dichotomy that the quotient algebra A/rad A determines the complexity of the d-fold multiplication in A: When the semisimple algebra A/rad A is commutative, then the multilinear complexity of the d-fold multiplication in A is polynomial in d. On the other hand, when A/rad A is noncommutative, then the multilinear complexity of the d-fold multiplication in A is exponential in d.
Cite as

Markus Bläser, Hendrik Mayer, and Devansh Shringi. On the Multilinear Complexity of Associative Algebras. In 40th International Symposium on Theoretical Aspects of Computer Science (STACS 2023). Leibniz International Proceedings in Informatics (LIPIcs), Volume 254, pp. 12:1-12:18, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2023)

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@InProceedings{blaser_et_al:LIPIcs.STACS.2023.12,
  author =	{Bl\"{a}ser, Markus and Mayer, Hendrik and Shringi, Devansh},
  title =	{{On the Multilinear Complexity of Associative Algebras}},
  booktitle =	{40th International Symposium on Theoretical Aspects of Computer Science (STACS 2023)},
  pages =	{12:1--12:18},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-266-2},
  ISSN =	{1868-8969},
  year =	{2023},
  volume =	{254},
  editor =	{Berenbrink, Petra and Bouyer, Patricia and Dawar, Anuj and Kant\'{e}, Mamadou Moustapha},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops-dev.dagstuhl.de/entities/document/10.4230/LIPIcs.STACS.2023.12},
  URN =		{urn:nbn:de:0030-drops-176645},
  doi =		{10.4230/LIPIcs.STACS.2023.12},
  annote =	{Keywords: Multilinear computations, associative algebras, matrix multiplication, Alder-Strassen theorem}
}
Document
DOI: 10.4230/OASIcs.ATMOS.2021.4
Solving the Home Service Assignment, Routing, and Appointment Scheduling (H-SARA) Problem with Uncertainties

Authors: Syu-Ning Johnn, Yiran Zhu, Andrés Miniguano-Trujillo, and Akshay Gupte

Published in: OASIcs, Volume 96, 21st Symposium on Algorithmic Approaches for Transportation Modelling, Optimization, and Systems (ATMOS 2021)

Abstract
The Home Service Assignment, Routing, and Appointment scheduling (H-SARA) problem integrates the strategic fleet-sizing, tactical assignment, operational vehicle routing and scheduling problems at different decision levels, with a single period planning horizon and uncertainty (stochasticity) from the service duration, travel time, and customer cancellation rate. We propose a stochastic mixed-integer linear programming model for the H-SARA problem. Additionally, a reduced deterministic version is introduced which allows to solve small-scale instances to optimality with two acceleration approaches. For larger instances, we develop a tailored two-stage decision support system that provides high-quality and in-time solutions based on information revealed at different stages. Our solution method aims to reduce various costs under stochasticity, to create reasonable routes with balanced workload and team-based customer service zones, and to increase customer satisfaction by introducing a two-stage appointment notification system updated at different time stages before the actual service. Our two-stage heuristic is competitive to CPLEX’s exact solution methods in providing time and cost-effective decisions and can update previously-made decisions based on an increased level of information. Results show that our two-stage heuristic is able to tackle reasonable-size instances and provides good-quality solutions using less time compared to the deterministic and stochastic models on the same set of simulated instances.
Cite as

Syu-Ning Johnn, Yiran Zhu, Andrés Miniguano-Trujillo, and Akshay Gupte. Solving the Home Service Assignment, Routing, and Appointment Scheduling (H-SARA) Problem with Uncertainties. In 21st Symposium on Algorithmic Approaches for Transportation Modelling, Optimization, and Systems (ATMOS 2021). Open Access Series in Informatics (OASIcs), Volume 96, pp. 4:1-4:21, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2021)

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@InProceedings{johnn_et_al:OASIcs.ATMOS.2021.4,
  author =	{Johnn, Syu-Ning and Zhu, Yiran and Miniguano-Trujillo, Andr\'{e}s and Gupte, Akshay},
  title =	{{Solving the Home Service Assignment, Routing, and Appointment Scheduling (H-SARA) Problem with Uncertainties}},
  booktitle =	{21st Symposium on Algorithmic Approaches for Transportation Modelling, Optimization, and Systems (ATMOS 2021)},
  pages =	{4:1--4:21},
  series =	{Open Access Series in Informatics (OASIcs)},
  ISBN =	{978-3-95977-213-6},
  ISSN =	{2190-6807},
  year =	{2021},
  volume =	{96},
  editor =	{M\"{u}ller-Hannemann, Matthias and Perea, Federico},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops-dev.dagstuhl.de/entities/document/10.4230/OASIcs.ATMOS.2021.4},
  URN =		{urn:nbn:de:0030-drops-148737},
  doi =		{10.4230/OASIcs.ATMOS.2021.4},
  annote =	{Keywords: Home Health Care, Mixed-Integer Linear Programming, Two-stage Stochastic, Uncertainties A Priori Optimisation, Adaptive Large Neighbourhood Search, Monte-Carlo Simulation}
}
Document
DOI: 10.4230/OASIcs.iPMVM.2020.14
Physical Modeling of Full-Field Time-Domain Optical Coherence Tomography

Authors: Andrej Keksel, Georgis Bulun, Matthias Eifler, Anis Idrizovic, and Jörg Seewig

Published in: OASIcs, Volume 89, 2nd International Conference of the DFG International Research Training Group 2057 – Physical Modeling for Virtual Manufacturing (iPMVM 2020)

Abstract
In this paper, a physical model of full-field time-domain optical coherence tomography (FF-TD OCT), which focuses the requirements of measuring inner textures of flexible layered samples in industrial applications, is developed and validated by reference measurements. Both the operating principle and the overall design of a FF-TD OCT correspond to that of classical white light interferometry (WLI), commonly used for the measurement of areal micro-topographies. The presented model accounts for optical and geometrical properties of the system, multiple scattering of light in turbid media and interference of partially coherent light. Applying this model, virtual measurements are used to exemplarily investigate the extent to which the principles of classical WLI can be directly transferred to obtain layer thickness measurements by simulating the use of a simple low-cost WLI system as OCT. Results indicate that a currently existing instrument setup can only be used as OCT to a very limited extent but not in general due to its initial design as a WLI.
Cite as

Andrej Keksel, Georgis Bulun, Matthias Eifler, Anis Idrizovic, and Jörg Seewig. Physical Modeling of Full-Field Time-Domain Optical Coherence Tomography. In 2nd International Conference of the DFG International Research Training Group 2057 – Physical Modeling for Virtual Manufacturing (iPMVM 2020). Open Access Series in Informatics (OASIcs), Volume 89, pp. 14:1-14:22, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2021)

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@InProceedings{keksel_et_al:OASIcs.iPMVM.2020.14,
  author =	{Keksel, Andrej and Bulun, Georgis and Eifler, Matthias and Idrizovic, Anis and Seewig, J\"{o}rg},
  title =	{{Physical Modeling of Full-Field Time-Domain Optical Coherence Tomography}},
  booktitle =	{2nd International Conference of the DFG International Research Training Group 2057 – Physical Modeling for Virtual Manufacturing (iPMVM 2020)},
  pages =	{14:1--14:22},
  series =	{Open Access Series in Informatics (OASIcs)},
  ISBN =	{978-3-95977-183-2},
  ISSN =	{2190-6807},
  year =	{2021},
  volume =	{89},
  editor =	{Garth, Christoph and Aurich, Jan C. and Linke, Barbara and M\"{u}ller, Ralf and Ravani, Bahram and Weber, Gunther H. and Kirsch, Benjamin},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops-dev.dagstuhl.de/entities/document/10.4230/OASIcs.iPMVM.2020.14},
  URN =		{urn:nbn:de:0030-drops-137634},
  doi =		{10.4230/OASIcs.iPMVM.2020.14},
  annote =	{Keywords: Optical coherence tomography, full-field time-domain OCT, virtual measuring, optical measurement technology, physical modeling}
}
Document
DOI: 10.4230/OASIcs.iPMVM.2020.16
Physical Modeling of Process Forces in Grinding

Authors: Praveen Sridhar, Daniel Mannherz, Raphael Bilz, Kristin M. de Payrebrune, Mahesh R.G. Prasad, and Juan Manuel Rodríguez Prieto

Published in: OASIcs, Volume 89, 2nd International Conference of the DFG International Research Training Group 2057 – Physical Modeling for Virtual Manufacturing (iPMVM 2020)

Abstract
This paper deals with material removal mechanisms in grinding by considering single grit-workpiece interactions. Individual investigations were performed both experimentally and using finite element simulations. Firstly, a comparison between the Johnson-Cooke material model and a Crystal Plasticity finite element method was performed with the help of micro-indentation experiments. Here the research question was answered if an anisotropic material model better describe the grinding process and process forces compared to an isotropic material model. Secondly, four discretization approaches were employed: pure Lagrangian (LAG), Arbitrary Lagrange Eulerian (ALE), Particle Finite Element Method (PFEM), and Smooth Particle Hydrodynamics (SPH), to simulate a micro-cutting operation of A2024 T351 aluminium. This study aims to compare the conventional approaches (LAG and ALE) to newer approaches (PFEM and SPH). The orthogonal cutting models were benchmarked against a micro-cutting experiment presented in literature, by comparing the obtained cutting and passive forces. The study was then extended to negative rake angles to study the effect on the discretization approaches for grinding. Thirdly, scratch experiments were investigated for a brittle material sodalime glass and A2024 T351 aluminium. Effects of the linear speed of the device, depth of cut, and conical tool angle were analyzed and tendencies are built. Finally, a realistic simulation of the manufacturing process of a grinding wheel was developed, starting with the raw material, compression, sintering, and dressing until the final grinding surface. As a result of the simulations, virtual grinding wheel topographies can be visualized and analyzed with regard to the output variables from grinding wheels such as bonding strength and static grain count. The individual research studies help in understanding the material removal mechanisms in a single grit scratch process as well as in the understanding of the overall grinding wheel topography. This in turn helps in the developing an overall physical force model for scratching/grinding to predict mechanical output parameters and hence reduce the need for experimentation.
Cite as

Praveen Sridhar, Daniel Mannherz, Raphael Bilz, Kristin M. de Payrebrune, Mahesh R.G. Prasad, and Juan Manuel Rodríguez Prieto. Physical Modeling of Process Forces in Grinding. In 2nd International Conference of the DFG International Research Training Group 2057 – Physical Modeling for Virtual Manufacturing (iPMVM 2020). Open Access Series in Informatics (OASIcs), Volume 89, pp. 16:1-16:20, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2021)

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@InProceedings{sridhar_et_al:OASIcs.iPMVM.2020.16,
  author =	{Sridhar, Praveen and Mannherz, Daniel and Bilz, Raphael and de Payrebrune, Kristin M. and Prasad, Mahesh R.G. and Prieto, Juan Manuel Rodr{\'\i}guez},
  title =	{{Physical Modeling of Process Forces in Grinding}},
  booktitle =	{2nd International Conference of the DFG International Research Training Group 2057 – Physical Modeling for Virtual Manufacturing (iPMVM 2020)},
  pages =	{16:1--16:20},
  series =	{Open Access Series in Informatics (OASIcs)},
  ISBN =	{978-3-95977-183-2},
  ISSN =	{2190-6807},
  year =	{2021},
  volume =	{89},
  editor =	{Garth, Christoph and Aurich, Jan C. and Linke, Barbara and M\"{u}ller, Ralf and Ravani, Bahram and Weber, Gunther H. and Kirsch, Benjamin},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops-dev.dagstuhl.de/entities/document/10.4230/OASIcs.iPMVM.2020.16},
  URN =		{urn:nbn:de:0030-drops-137651},
  doi =		{10.4230/OASIcs.iPMVM.2020.16},
  annote =	{Keywords: grinding, single grit approach, finite element method, smooth particle hydrodynamics, particle finite element method, scratch experiments, virtual grinding wheel model}
}
Document
DOI: 10.4230/LIPIcs.ITCS.2017.24
Nondeterministic Quantum Communication Complexity: the Cyclic Equality Game and Iterated Matrix Multiplication

Authors: Harry Buhrman, Matthias Christandl, and Jeroen Zuiddam

Published in: LIPIcs, Volume 67, 8th Innovations in Theoretical Computer Science Conference (ITCS 2017)

Abstract
We study nondeterministic multiparty quantum communication with a quantum generalization of broadcasts. We show that, with number-in-hand classical inputs, the communication complexity of a Boolean function in this communication model equals the logarithm of the support rank of the corresponding tensor, whereas the approximation complexity in this model equals the logarithm of the border support rank. This characterisation allows us to prove a log-rank conjecture posed by Villagra et al. for nondeterministic multiparty quantum communication with message passing. The support rank characterization of the communication model connects quantum communication complexity intimately to the theory of asymptotic entanglement transformation and algebraic complexity theory. In this context, we introduce the graphwise equality problem. For a cycle graph, the complexity of this communication problem is closely related to the complexity of the computational problem of multiplying matrices, or more precisely, it equals the logarithm of the support rank of the iterated matrix multiplication tensor. We employ Strassen’s laser method to show that asymptotically there exist nontrivial protocols for every odd-player cyclic equality problem. We exhibit an efficient protocol for the 5-player problem for small inputs, and we show how Young flattenings yield nontrivial complexity lower bounds.
Cite as

Harry Buhrman, Matthias Christandl, and Jeroen Zuiddam. Nondeterministic Quantum Communication Complexity: the Cyclic Equality Game and Iterated Matrix Multiplication. In 8th Innovations in Theoretical Computer Science Conference (ITCS 2017). Leibniz International Proceedings in Informatics (LIPIcs), Volume 67, pp. 24:1-24:18, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2017)

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@InProceedings{buhrman_et_al:LIPIcs.ITCS.2017.24,
  author =	{Buhrman, Harry and Christandl, Matthias and Zuiddam, Jeroen},
  title =	{{Nondeterministic Quantum Communication Complexity: the Cyclic Equality Game and Iterated Matrix Multiplication}},
  booktitle =	{8th Innovations in Theoretical Computer Science Conference (ITCS 2017)},
  pages =	{24:1--24:18},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-029-3},
  ISSN =	{1868-8969},
  year =	{2017},
  volume =	{67},
  editor =	{Papadimitriou, Christos H.},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops-dev.dagstuhl.de/entities/document/10.4230/LIPIcs.ITCS.2017.24},
  URN =		{urn:nbn:de:0030-drops-81812},
  doi =		{10.4230/LIPIcs.ITCS.2017.24},
  annote =	{Keywords: quantum communication complexity, broadcast channel, number-in-hand, matrix multiplication, support rank}
}
Document
DOI: 10.4230/LIPIcs.ICALP.2017.33
Reordering Buffer Management with a Logarithmic Guarantee in General Metric Spaces

Authors: Matthias Kohler and Harald Räcke

Published in: LIPIcs, Volume 80, 44th International Colloquium on Automata, Languages, and Programming (ICALP 2017)

Abstract
In the reordering buffer management problem a sequence of requests arrive online in a finite metric space, and have to be processed by a single server. This server is equipped with a request buffer of size k and can decide at each point in time, which request from its buffer to serve next. Servicing of a request is simply done by moving the server to the location of the request. The goal is to process all requests while minimizing the total distance that the server is traveling inside the metric space. In this paper we present a deterministic algorithm for the reordering buffer management problem that achieves a competitive ratio of O(log Delta + min {log n,log k}) in a finite metric space of n points and aspect ratio Delta. This is the first algorithm that works for general metric spaces and has just a logarithmic dependency on the relevant parameters. The guarantee is memory-robust, i.e., the competitive ratio decreases only slightly when the buffer-size of the optimum is increased to h=(1+\epsilon)k. For memory robust guarantees our bounds are close to optimal.
Cite as

Matthias Kohler and Harald Räcke. Reordering Buffer Management with a Logarithmic Guarantee in General Metric Spaces. In 44th International Colloquium on Automata, Languages, and Programming (ICALP 2017). Leibniz International Proceedings in Informatics (LIPIcs), Volume 80, pp. 33:1-33:12, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2017)

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@InProceedings{kohler_et_al:LIPIcs.ICALP.2017.33,
  author =	{Kohler, Matthias and R\"{a}cke, Harald},
  title =	{{Reordering Buffer Management with a Logarithmic Guarantee in General Metric Spaces}},
  booktitle =	{44th International Colloquium on Automata, Languages, and Programming (ICALP 2017)},
  pages =	{33:1--33:12},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-041-5},
  ISSN =	{1868-8969},
  year =	{2017},
  volume =	{80},
  editor =	{Chatzigiannakis, Ioannis and Indyk, Piotr and Kuhn, Fabian and Muscholl, Anca},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops-dev.dagstuhl.de/entities/document/10.4230/LIPIcs.ICALP.2017.33},
  URN =		{urn:nbn:de:0030-drops-73882},
  doi =		{10.4230/LIPIcs.ICALP.2017.33},
  annote =	{Keywords: Online algorithms, reordering buffer, metric spaces, scheduling}
}
Document
DOI: 10.4230/LIPIcs.FSTTCS.2012.412
Beyond Max-Cut: lambda-Extendible Properties Parameterized Above the Poljak-Turzik Bound

Authors: Matthias Mnich, Geevarghese Philip, Saket Saurabh, and Ondrej Suchy

Published in: LIPIcs, Volume 18, IARCS Annual Conference on Foundations of Software Technology and Theoretical Computer Science (FSTTCS 2012)

Abstract
Poljak and Turzík (Discrete Math. 1986) introduced the notion of lambda-extendible properties of graphs as a generalization of the property of being bipartite. They showed that for any 0 < lambda < 1 and lambda-extendible property Pi, any connected graph G on n vertices and m edges contains a spanning subgraph H in Pi with at least lambda m+ (1-lambda)/2 (n-1) edges. The property of being bipartite is lambda-extendible for lambda=1/2, and thus the Poljak-Turzík bound generalizes the well-known Edwards-Erdos bound for MAXCUT. We define a variant, namely strong lambda-extendibility, to which the Poljak-Turzík bound applies. For a strong lambda-extendible graph property \Pi, we define the parameterized Above Poljak-Turzík problem as follows: Given a connected graph G on n vertices and m edges and an integer parameter k, does there exist a spanning subgraph H of G such that H in Pi and H has at least lambda m+ (1-lambda)/2 (n-1)+k edges? The parameter is k, the surplus over the number of edges guaranteed by the Poljak-Turzík bound. We consider properties Pi for which the Above Poljak-Turzík problem is fixed-parameter tractable (FPT) on graphs which are O(k) vertices away from being a graph in which each block is a clique. We show that for all such properties, Above Poljak-Turzík is FPT for all 0< lambda <1. Our results hold for properties of oriented graphs and graphs with edge labels. Our results generalize the recent result of Crowston et al. (ICALP 2012) on MAXCUT parameterized above the Edwards-Erdos, and yield FPT algorithms for several graph problems parameterized above lower bounds. For instance, we get that the above-guarantee Max q-Colorable Subgraph problem is FPT. Our results also imply that the parameterized above-guarantee Oriented Max Acyclic Digraph problem thus solving an open question of Raman and Saurabh (Theor. Comput. Sci. 2006).
Cite as

Matthias Mnich, Geevarghese Philip, Saket Saurabh, and Ondrej Suchy. Beyond Max-Cut: lambda-Extendible Properties Parameterized Above the Poljak-Turzik Bound. In IARCS Annual Conference on Foundations of Software Technology and Theoretical Computer Science (FSTTCS 2012). Leibniz International Proceedings in Informatics (LIPIcs), Volume 18, pp. 412-423, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2012)

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@InProceedings{mnich_et_al:LIPIcs.FSTTCS.2012.412,
  author =	{Mnich, Matthias and Philip, Geevarghese and Saurabh, Saket and Suchy, Ondrej},
  title =	{{Beyond Max-Cut:  lambda-Extendible Properties Parameterized Above the Poljak-Turzik Bound}},
  booktitle =	{IARCS Annual Conference on Foundations of Software Technology and Theoretical Computer Science (FSTTCS 2012)},
  pages =	{412--423},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-939897-47-7},
  ISSN =	{1868-8969},
  year =	{2012},
  volume =	{18},
  editor =	{D'Souza, Deepak and Radhakrishnan, Jaikumar and Telikepalli, Kavitha},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops-dev.dagstuhl.de/entities/document/10.4230/LIPIcs.FSTTCS.2012.412},
  URN =		{urn:nbn:de:0030-drops-38776},
  doi =		{10.4230/LIPIcs.FSTTCS.2012.412},
  annote =	{Keywords: Algorithms and data structures; fixed-parameter algorithms; bipartite graphs; above-guarantee parameterization}
}
Document
DOI: 10.4230/OASIcs.GCB.2012.69
ConReg: Analysis and Visualization of Conserved Regulatory Networks in Eukaryotes

Authors: Robert Pesch, Matthias Böck, and Ralf Zimmer

Published in: OASIcs, Volume 26, German Conference on Bioinformatics 2012

Abstract
Transcription factors (TFs) play a fundamental role in cellular regulation by binding to promoter regions of target genes (TGs) in order to control their gene expression. TF-TG networks are widely used as representations of regulatory mechanisms, e.g. for modeling the cellular response to input signals and perturbations. As the experimental identification of regulatory interactions is time consuming and expensive, one tries to use knowledge from related species when studying an organism of interest. Here, we present ConReg, an interactive web application to store regulatory relations for various species and to investigate their level of conservation in related species. Currently, ConReg contains data for eight model organisms. The regulatory relations stored in publicly available databases cover only a small fraction both of the actual interactions and also of the regulatory relations described in the scientific literature. Therefore, we included regulatory relations extracted from PubMed and PubMedCentral using sophisticated text-mining approaches and from binding site predictions into ConReg. We applied ConReg for the investigation of conserved regulatory motifs in D. melanogaster. From the 471 regulatory relations in REDfly our system was able to identify 66 confirmed conserved regulations in at least one vertebrate model organism (H. sapiens, M. musculus, R. norvegicus, D. rerio). The conserved network consists among others of the well studied motifs for eye-development and the pan-bilaterian kernel for heart specification, which are well-known examples for conserved regulatory relations between different organisms. ConReg is available at http://services.bio.ifi.lmu.de/ConReg/ and can be used to analyze and visualize regulatory networks and their conservation among eight model organisms. It also provides direct links to annotations including literature references to potentially conserved regulatory relations.
Cite as

Robert Pesch, Matthias Böck, and Ralf Zimmer. ConReg: Analysis and Visualization of Conserved Regulatory Networks in Eukaryotes. In German Conference on Bioinformatics 2012. Open Access Series in Informatics (OASIcs), Volume 26, pp. 69-81, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2012)

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@InProceedings{pesch_et_al:OASIcs.GCB.2012.69,
  author =	{Pesch, Robert and B\"{o}ck, Matthias and Zimmer, Ralf},
  title =	{{ConReg: Analysis and Visualization of Conserved Regulatory Networks in Eukaryotes}},
  booktitle =	{German Conference on Bioinformatics 2012},
  pages =	{69--81},
  series =	{Open Access Series in Informatics (OASIcs)},
  ISBN =	{978-3-939897-44-6},
  ISSN =	{2190-6807},
  year =	{2012},
  volume =	{26},
  editor =	{B\"{o}cker, Sebastian and Hufsky, Franziska and Scheubert, Kerstin and Schleicher, Jana and Schuster, Stefan},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops-dev.dagstuhl.de/entities/document/10.4230/OASIcs.GCB.2012.69},
  URN =		{urn:nbn:de:0030-drops-37194},
  doi =		{10.4230/OASIcs.GCB.2012.69},
  annote =	{Keywords: web application, evolutionary biology, regulatory networks, text-mining}
}
Document
DOI: 10.4230/DagMan.2.1.1
Social, Supply-Chain, Administrative, Business, Commerce, Political networks: a multi-discipline perspective (Dagstuhl Perspectives Workshop 12182)

Authors: Matthias Häsel, Thorsten Quandt, and Gottfried Vossen

Published in: Dagstuhl Manifestos, Volume 2, Issue 1 (2012)

Abstract
This is the manifesto of Dagstuhl Perspectives Workshop 12182 on a multi-discipline perspective on networks. The information society is shaped by an increasing presence of networks in various manifestations, most notably computer networks, supply-chain networks, and social networks, but also business networks, administrative networks, or political networks. Online networks nowadays connect people all around the world at day and night, and allow to communicate and to work collaboratively and efficiently. What has been a commodity in the private as well as in the enterprise sectors independently for quite some time now is currently growing together at an increasing pace. As a consequence, the time has come for the relevant sciences, including computer science, information systems, social sciences, economics, communication sciences, and others, to give up their traditional "silo-style" thinking and enter into borderless dialogue and interaction. The purpose of this Manifesto is to review where we stand today, and to outline directions in which we urgently need to move, in terms of both research and teaching, but also in terms of funding.
Cite as

Matthias Häsel, Thorsten Quandt, and Gottfried Vossen. Social, Supply-Chain, Administrative, Business, Commerce, Political networks: a multi-discipline perspective (Dagstuhl Perspectives Workshop 12182). In Dagstuhl Manifestos, Volume 2, Issue 1, pp. 1-13, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2012)

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@Article{hasel_et_al:DagMan.2.1.1,
  author =	{H\"{a}sel, Matthias and Quandt, Thorsten and Vossen, Gottfried},
  title =	{{Social, Supply-Chain, Administrative, Business, Commerce, Political networks: a multi-discipline perspective (Dagstuhl Perspectives Workshop 12182)}},
  pages =	{1--13},
  journal =	{Dagstuhl Manifestos},
  ISSN =	{2193-2433},
  year =	{2012},
  volume =	{2},
  number =	{1},
  editor =	{H\"{a}sel, Matthias and Quandt, Thorsten and Vossen, Gottfried},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops-dev.dagstuhl.de/entities/document/10.4230/DagMan.2.1.1},
  URN =		{urn:nbn:de:0030-drops-36542},
  doi =		{10.4230/DagMan.2.1.1},
  annote =	{Keywords: Networks, network infrastructure, network types, network effects, data in networks, social networks, social media, crowdsourcing}
}
Document
DOI: 10.4230/DagSemProc.08031.2
08031 – Software Engineering for Self-Adaptive Systems: A Research Road Map

Authors: Betty H.C. Cheng, Holger Giese, Paola Inverardi, Jeff Magee, Rogerio de Lemos, Jesper Andersson, Basil Becker, Nelly Bencomo, Yuriy Brun, Bojan Cukic, Giovanna Di Marzo Serugendo, Schahram Dustdar, Anthony Finkelstein, Cristina Gacek, Kurt Geihs, Vincenzo Grassi, Gabor Karsai, Holger Kienle, Jeff Kramer, Marin Litoiu, Sam Malek, Raffaela Mirandola, Hausi Müller, Sooyong Park, Mary Shaw, Matthias Tichy, Massimo Tivoli, Danny Weyns, and Jon Whittle

Published in: Dagstuhl Seminar Proceedings, Volume 8031, Software Engineering for Self-Adaptive Systems (2008)

Abstract
Software's ability to adapt at run-time to changing user needs, system intrusions or faults, changing operational environment, and resource variability has been proposed as a means to cope with the complexity of today's software-intensive systems. Such self-adaptive systems can configure and reconfigure themselves, augment their functionality, continually optimize themselves, protect themselves, and recover themselves, while keeping most of their complexity hidden from the user and administrator. In this paper, we present research road map for software engineering of self-adaptive systems focusing on four views, which we identify as essential: requirements, modelling, engineering, and assurances.
Cite as

Betty H.C. Cheng, Holger Giese, Paola Inverardi, Jeff Magee, Rogerio de Lemos, Jesper Andersson, Basil Becker, Nelly Bencomo, Yuriy Brun, Bojan Cukic, Giovanna Di Marzo Serugendo, Schahram Dustdar, Anthony Finkelstein, Cristina Gacek, Kurt Geihs, Vincenzo Grassi, Gabor Karsai, Holger Kienle, Jeff Kramer, Marin Litoiu, Sam Malek, Raffaela Mirandola, Hausi Müller, Sooyong Park, Mary Shaw, Matthias Tichy, Massimo Tivoli, Danny Weyns, and Jon Whittle. 08031 – Software Engineering for Self-Adaptive Systems: A Research Road Map. In Software Engineering for Self-Adaptive Systems. Dagstuhl Seminar Proceedings, Volume 8031, pp. 1-13, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2008)

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@InProceedings{cheng_et_al:DagSemProc.08031.2,
  author =	{Cheng, Betty H.C. and Giese, Holger and Inverardi, Paola and Magee, Jeff and de Lemos, Rogerio and Andersson, Jesper and Becker, Basil and Bencomo, Nelly and Brun, Yuriy and Cukic, Bojan and Di Marzo Serugendo, Giovanna and Dustdar, Schahram and Finkelstein, Anthony and Gacek, Cristina and Geihs, Kurt and Grassi, Vincenzo and Karsai, Gabor and Kienle, Holger and Kramer, Jeff and Litoiu, Marin and Malek, Sam and Mirandola, Raffaela and M\"{u}ller, Hausi and Park, Sooyong and Shaw, Mary and Tichy, Matthias and Tivoli, Massimo and Weyns, Danny and Whittle, Jon},
  title =	{{08031 – Software Engineering for Self-Adaptive Systems: A Research Road Map}},
  booktitle =	{Software Engineering for Self-Adaptive Systems},
  pages =	{1--13},
  series =	{Dagstuhl Seminar Proceedings (DagSemProc)},
  ISSN =	{1862-4405},
  year =	{2008},
  volume =	{8031},
  editor =	{Betty H. C. Cheng and Rogerio de Lemos and Holger Giese and Paola Inverardi and Jeff Magee},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops-dev.dagstuhl.de/entities/document/10.4230/DagSemProc.08031.2},
  URN =		{urn:nbn:de:0030-drops-15008},
  doi =		{10.4230/DagSemProc.08031.2},
  annote =	{Keywords: Software engineering, requirements engineering, modelling, evolution, assurances, self-adaptability, self-organization, self-management}
}
Document
DOI: 10.4230/OASIcs.ATMOS.2005.657
Paying Less for Train Connections with MOTIS

Authors: Matthias Müller-Hannemann and Mathias Schnee

Published in: OASIcs, Volume 2, 5th Workshop on Algorithmic Methods and Models for Optimization of Railways (ATMOS'05) (2006)

Abstract
Finding cheap train connections for long-distance traffic is algorithmically a hard task due to very complex tariff regulations. Several new tariff options have been developed in recent years, partly to react on the stronger competition with low-cost airline carriers. In such an environment, it becomes more and more important that search engines for travel connections are able to find special offers efficiently. We have developed a multi-objective traffic information system (MOTIS) which finds all attractive train connections with respect to travel time, number of interchanges, and ticket costs. In contrast, most servers for timetable information as well as the theoretical literature on this subject focus only on travel time as the primary objective, and secondary objectives like the number of interchanges are treated only heuristically. The purpose of this paper is to show by means of a case study how several of the most common tariff rules (including special offers) can be embedded into a general multi-objective search tool. Computational results show that a multi-objective search with a mixture of tariff rules can be done almost as fast as just with one regular tariff. For the train schedule of Germany, a query can be answered within 1.9s on average on a standard PC.
Cite as

Matthias Müller-Hannemann and Mathias Schnee. Paying Less for Train Connections with MOTIS. In 5th Workshop on Algorithmic Methods and Models for Optimization of Railways (ATMOS'05). Open Access Series in Informatics (OASIcs), Volume 2, pp. 1-19, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2006)

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@InProceedings{mullerhannemann_et_al:OASIcs.ATMOS.2005.657,
  author =	{M\"{u}ller-Hannemann, Matthias and Schnee, Mathias},
  title =	{{Paying Less for Train Connections with MOTIS}},
  booktitle =	{5th Workshop on Algorithmic Methods and Models for Optimization of Railways (ATMOS'05)},
  pages =	{1--19},
  series =	{Open Access Series in Informatics (OASIcs)},
  ISBN =	{978-3-939897-00-2},
  ISSN =	{2190-6807},
  year =	{2006},
  volume =	{2},
  editor =	{Kroon, Leo G. and M\"{o}hring, Rolf H.},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops-dev.dagstuhl.de/entities/document/10.4230/OASIcs.ATMOS.2005.657},
  URN =		{urn:nbn:de:0030-drops-6572},
  doi =		{10.4230/OASIcs.ATMOS.2005.657},
  annote =	{Keywords: Timetable information system, multi-criteria optimization, shortest paths, fares, special offers, long-distance traffic}
}
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