- informatik-vortraege - lists.rwth-aachen.de

Einladung: Informatik-Oberseminar Andrea Schnorr
by Andrea Schnorr 03 Jul '21

03 Jul '21

+********************************************************************** * * * Einladung * * * * Informatik-Oberseminar * * * +********************************************************************** Zeit: Freitag, 19. Februar 2021, 11.00 Uhr Zoom: https://rwth.zoom.us/j/2452218628 Referent: Andrea Schnorr, M.Sc. LuFG i12 Thema: Feature Tracking for Space-Filling Structures Abstract: Feature-based visualization is a proven strategy to deal with the massive amounts of data emerging from time-dependent simulations: the analysis focuses on meaningful structures, i.e., said features. Feature tracking algorithms aim at automatically finding corresponding objects in successive time steps of these time-dependent data sets in order to assemble the individual objects into spatio-temporal features. Classically, feature-based visualization has focused on sparse structures, i.e. structures which cover only a small portion of the data domain. Given a sufficiently high temporal resolution, existing tracking approaches are able to reliably resolve the correspondence between feature objects of successive time steps. Our research is motivated by our collaborators' work on the statistical analysis of structures that are space-filling by definition: dissipation elements. Space-filling structures partition the entire domain. Our collaborators aim at extending their statistical analysis to a time-dependent setting. Hence, we introduce an efficient approach for general feature tracking which handles both sparse and space-filling data. To this end, we develop a framework for automatic evaluation of tracking approaches, an algorithmic framework for feature tracking, and an efficient implementation of this framework. First, we propose a novel evaluation framework based on algorithmic data generators, which provide synthetic data sets and the corresponding ground truth data. This framework facilitates the structured quantitative analysis of an approach's feature tracking performance and the comparison of different approaches based on the resulting measurements. Second, we introduce a novel approach for tracking both sparse and space-filling features. The correspondence between neighboring time-steps is determined by successively solving two graph optimization problems. In the first phase, one-to-one assignments are resolved by computing a maximum-weight, maximum-cardinality matching on a bi-partite graph. In its second phase, the algorithm detects events by finding a maximum weight independent set in a graph of all possible, potentially conflicting event explanations. Third, we show an optimized version of the second stage of the tracking framework which exploits the model-specific graph structure arising for the tracking problem. The method's effectiveness is demonstrated by a set of case studies including the use of the evaluation framework as well as the analysis of miscellaneous real-world simulation data sets. Es laden ein: die Dozentinnen und Dozenten der Informatik

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Einladung: Informatik-Oberseminar Herr Peter Marcel de Lange
by Leany Maaßen 17 Jun '21

17 Jun '21

+********************************************************************** * * * Einladung * * * * Informatik-Oberseminar * * * +********************************************************************** Zeit: Dienstag, 20. Juli 2021, 10:00-11:00 Uhr Zoom: <https://rwth.zoom.us/j/93538347394?pwd=YXlqZ1VqSE0vRjRnclRtQTY5RVJOZz09> https://rwth.zoom.us/j/93538347394?pwd=YXlqZ1VqSE0vRjRnclRtQTY5RVJOZz09 Meeting-ID: 935 3834 7394 Kenncode: 388699 Referent: Herr Peter Marcel de Lange, M.Sc. Lehrstuhl Informatik 5 Thema: Scaffolding Decentralized Community Information Systems for Lifelong Learning Communities Abstract: With the rise of the Web 2.0, social networking sites and content management systems enabled professional communities to create Web content. But it simultaneously put the communities at the mercy of the platform operators and software providers. Decentralized community information systems bring in a new perspective by offering self-hosting, self-governing and self-developing communities. In this dissertation, we followed a design science approach that provides support for communities to create and host their own, decentralized community information systems. On the one hand, we produced several artifacts to provide possible answers to the question of what properties such an infrastructure needs to fulfill. On the other hand, we transfer the metaphor of educational scaffolding to the domain of service development. We demonstrated and evaluated our open source artifacts on a European scale, with three longitudinal studies conducted within several communities from different areas of technology enhanced learning, such as the European voluntary service, vocational and educational training providers and in higher education mentoring scenarios. Es laden ein: die Dozentinnen und Dozenten der Informatik _______________________________ Leany Maaßen RWTH Aachen University Lehrstuhl Informatik 5, LuFG Informatik 5 Prof. Dr. Stefan Decker, Prof. Dr. Matthias Jarke, Prof. Gerhard Lakemeyer Ph.D. Ahornstrasse 55 D-52074 Aachen Tel: 0241-80-21509 Fax: 0241-80-22321 E-Mail: maassen(a)dbis.rwth-aachen.de

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Ankündigung: Informatik-Oberseminar
by Thönnessen, David 15 Jun '21

15 Jun '21

+********************************************************************** * * * Einladung * * * * Informatik-Oberseminar * * * +********************************************************************** Zeit: Montag, 21. Juni 2021, 13.00 Uhr Ort: Videokonferenz (Zoom-Meeting, Informationen siehe unten) Referent: David Thönnessen, M.Sc. Lehrstuhl Informatik 11 Thema: Hardware-in-the-Loop Testing of Industrial Automation Systems Using PLC Languages Abstract: Testing industrial controllers such as Programmable Logic Controllers (PLCs) poses specific challenges to the test process. Especially in the context of Cyber-Physical Production System (CPPS) the control systems are subject to continuous reconfiguration. Therefore, it is no longer sufficient to test solely before commissioning, but it must be possible to test existing control systems after their reconfiguration with low effort and to put them back into operation. Our approach for this is to develop a test environment that allows an efficient and modular test case specification and can therefore be easily adapted to changing environmental conditions. We have chosen Hardware-in-the-Loop (HiL) simulation as the basis for this test environment since not only the control model or control program is included in the test, but also the control hardware. Our architecture uses slightly extended PLC programming languages to specify test cases. Thus, we avoid the change in methodology that occurs when using dedicated test case specification languages and corresponding test environments. Furthermore, we have provided our concept with the possibility of randomized test case generation, such that a large number of test cases can be generated and tested without a tester having to specify them manually. Our hypothesis is that this will lead to faster and more reliable customizable test cases and thus create the desired agility. The evaluation of our implementation shows that especially developers who are familiar with PLC programming languages can achieve an increase in testing efficiency compared to existing test tools. Furthermore, by randomized testing of Safety Programmable Logic Controllers (Safety PLCs), we show that our test tool can find critical errors in control systems, which would have been found with traditional test methods only to a limited extent. From these results we conclude that the concept presented here is a valuable addition to existing test methods and well-tailored to the challenges of CPPS. Es laden ein: die Dozentinnen und Dozenten der Informatik +********************************************************************** Thema: PhD Defense David Thönnessen Uhrzeit: 21.Juni.2021 01:00 PM Amsterdam, Berlin, Rom, Stockholm, Wien Zoom-Meeting beitreten https://rwth.zoom.us/j/96024814962?pwd=eEU5SmNFTjYyWitJVldVRmQ3TE5pdz09 Meeting-ID: 960 2481 4962 Kenncode: 158094 +**********************************************************************

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Einladung: Informatik-Kolloquium Prof. Stephan Günnemann, 15. Juni um 14h
by Gerhard Lakemeyer 09 Jun '21

09 Jun '21

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Einladung: Informatik-Oberseminar Herr Sevket Gökay
by Leany Maaßen 02 Jun '21

02 Jun '21

+********************************************************************** * * * Einladung * * * * Informatik-Oberseminar * * * +********************************************************************** Zeit: Dienstag, 15. Juni 2021, 14:00-15:00 Uhr Zoom: https://rwth.zoom.us/j/95286197657?pwd=TWtHZHBpa3Q4bmNIZUZXZ21NSmdydz09 Meeting-ID: 952 8619 7657 Kenncode: 048149 Referent: Herr Dipl.-Inform. Sevket Gökay Lehrstuhl Informatik 5 Thema: Scalable Real-Time Ride-Sharing with Meeting Points for Flexible On-Demand Public Transportation Abstract: The landscape of personal transportation is colorful and ever-changing. Ride-sharing, a member of the on-demand transportation family, sits between the private and public transportation categories. It can transport multiple passengers with similar journeys in the same vehicle in a flexible and convenient manner. This work explores real-time ride-sharing in three steps. First, we develop and evaluate a dynamic (i.e. flexible, on-demand) bus-like service as an alternative to the traditional bus service in rural areas with low demand. Simulations conducted in Aachen and in Ulm indicate that both the providers and the customers might benefit from this alternative. Next, we address the computational scalability issue of the service in urban areas with high demand. We present an approach to reduce processing time by employing an improved trip-vehicle fitness heuristic. The evaluation simulates New York City taxi trips in a ride-sharing context, and exhibits significant performance improvement, together with improved customer satisfaction and vehicle costs. Finally, we investigate the prevention of small detours of vehicles, by merging location visits with close proximity into one by introducing small walking paths. The results hint at a significant increase in the number of satisfied trip requests. Es laden ein: die Dozentinnen und Dozenten der Informatik _______________________________ Leany Maaßen RWTH Aachen University Lehrstuhl Informatik 5, LuFG Informatik 5 Prof. Dr. Stefan Decker, Prof. Dr. Matthias Jarke, Prof. Gerhard Lakemeyer Ph.D. Ahornstrasse 55 D-52074 Aachen Tel: 0241-80-21509 Fax: 0241-80-22321 E-Mail: maassen(a)dbis.rwth-aachen.de

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Einladung: Informatik-Oberseminar Daniel Wiebking
by Daniel Wiebking 01 Jun '21

01 Jun '21

+********************************************************************** * * * Einladung * * * * Informatik-Oberseminar * * * +********************************************************************** Zeit: Montag, 14. Juni 2021, 16:00 Uhr Ort: Zoom Videokonferenz Link: https://rwth.zoom.us/j/94470149252?pwd=ZnYwVXQrbStveVdDNDk1V1BlN1lJUT09 Meeting-ID: 944 7014 9252 Kenncode: 004247 Referent: Daniel Wiebking, M.Sc. Lehrstuhl Informatik 7 Thema: A Decomposition-Compatible Canonization Framework for the Graph Isomorphism Problem Abstract: The Graph Isomorphism Problem is one of a few famous problems in NP that is neither known to be solvable in polynomial time nor to be NP-complete. The problem asks whether two given input graphs are structurally equivalent, which means that both graphs coincide up to a renaming of the vertices. With Babai's celebrated breakthrough (STOC 2016) it was shown that the problem can be decided in quasipolynomial time. One way of solving the Graph Isomorphism Problem is by applying a canonization approach. Graph canonization is the task of transforming a graph into a canonical form, that is, a graph representation that coincides for structurally equivalent graphs. As far as we know, graph canonization might be harder than the Graph Isomorphism Problem. In particular, there are isomorphism tests for various graph classes and objects for which to date no canonization algorithm with the same asymptotic running time is known. In this thesis, we devise a unified canonization framework for graphs, and beyond that for combinatorial objects in general. We use that framework to design new fastest canonization algorithms with an asymptotic running time matching the best known isomorphism tests. Our framework supports the use of decomposition techniques. By combining our framework with new graph-theoretic decompositions, we not only match but even improve the running time of existing isomorphism tests for graphs of bounded treewidth and graphs excluding fixed minors. Our improved algorithms for restricted graph classes come hand in hand with new insights about the automorphism groups. We prove several restrictions on these groups by analyzing them from a purely mathematical point of view. Beyond that, our decomposition-friendly framework has also applications in computational group theory. In particular, we design a new fastest algorithm computing normalizers of permutation groups. Finally, we investigate the connections between isomorphism testing and canonization from a logical perspective. To this end, we provide a new computation model that supports a construction turning isomorphism tests into canonization algorithms. Es laden ein: die Dozentinnen und Dozenten der Informatik

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Einladung: Informatik-Kolloquium Holger Hoos
by Martin Grohe 31 May '21

31 May '21

********************************************************************** * * * Einladung * * * * Informatik-Kolloquium * * * ********************************************************************** Zeit: Dienstag, 8. Juni 2021, 14:00 Uhr Ort: https://rwth.zoom.us/j/98025555800?pwd=SUgxYWR3RGxnaGNMZGg5bmNqeGZYQT09 Meeting-ID: 980 2555 5800 Kenncode: 419493 ********************************************************************** Vortragender: Holger H. Hoos (Universität Leiden) Titel: Cooperative competition: A new way of solving computationally challenging problems in AI and beyond Abstract: Progress in solving challenging problems in artificial intelligence, computer science at large, and beyond is driven, to a significant extent, by competition - regular algorithm competitions as well as comparative performance evaluation against state-of-the-art methods from the literature. A prominent example for this is the satisfiability problem in propositional logic (SAT), an NP-hard problem that not only lies at the foundations of computer science, but also plays a key role in many real-world applications, notably in ensuring the correctness of hard- and software. In this presentation, I will argue that it is time to rethink the way we assess the state of the art in solving problems such as SAT and the incentives for improving it. I will demonstrate how automated algorithm selection and configuration techniques based on sophisticated machine learning and optimisation methods have fundamentally changed not only the state of the art in solving SAT and many other NP-hard problems, but also provide a natural basis for cooperative competition - a new approach for achieving and assessing progress not merely in solving these problems, but also in the way we approach them as a scientific community. Es laden ein: die Dozentinnen und Dozenten der Informatik

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Einladung: Informatik-Oberseminar Bastian Küppers
by Küppers, Bastian 28 May '21

28 May '21

+********************************************************************** * * * Einladung * * * * Informatik-Oberseminar * * * +********************************************************************** Zeit: Montag, 28. Juni 2021, 14.00 Uhr Ort: https://rwth.zoom.us/my/b.kueppers?pwd=dDFyZkJvUDRFbFlFbnh0R3hQZVVRdz09 Referent: Bastian Küppers, M.Sc. IT Center / Learning Technologies Research Group Thema: Development of a Framework for E-Assessment on Students’ Devices Abstract: In line with the general trend towards digitization, teaching at German universities is increasingly relying on digital elements, such as learning management systems or smartphone apps. This evolution is also taking place in exercises and practical courses associated with lectures. For example, it is quite common for students to use their own devices in programming exercises. However, examinations are not yet part of this development. The decision to continue writing exams on paper is often made based on reservations, most of which concern the fairness and reliability of e-assessment. In particular, students’ reservations, because they may feel responsible for a functioning device, are a major obstacle to the introduction of e-Assessment. It is therefore important to overcome these reservations, to be able to successfully implement e-assessment. In addition to reservations, financial reasons are often an obstacle. The acquisition and administration of a suitable IT infrastructure is expensive, both in terms of material costs and personnel costs. Since the majority of students already own devices that are potentially suitable for e-assessment, Bring Your Own Device (BYOD) is a possible solution to the financial aspect. However, a BYOD approach to e-assessment comes with new challenges that have to be tackled. On the way to a solution that works in the previously described scenario, requirements engineering has been a vital part of the process. Therefore, students and teachers as well as official policies have been consulted to derive the requirements to a feasible BYOD approach to e-assessment. In addition to the found requirements, a threat model has been developed to identify additional requirements to the security of such an approach. Afterwards, a software framework was developed and implemented which fulfilled the gathered requirements. Finally, the software prototype was evaluated regarding functionality, usability, performance, and security. Beyond the software prototype, an organizational framework has been developed which covers (hardware) requirements for the institute of higher education as well as important organizational details for the conduction of electronic assessment. In this talk, we discuss important key points of the research process and present the results of our work. Es laden ein: die Dozentinnen und Dozenten der Informatik

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Einladung: Informatik-Oberseminar Marcel Hark
by Marcel Hark 25 May '21

25 May '21

+********************************************************************** * * * Einladung * * * * Informatik-Oberseminar * * * +********************************************************************** Zeit: Freitag, 18. Juni 2021, 15.00 Uhr Ort: Zoom-Videokonferenz Link: https://rwth.zoom.us/j/94806153993?pwd=dUIwQWYxNUx1cG1jOEpLc25WdmJwUT09 Referent: Marcel Hark M.Sc. Lehr- und Forschungsgebiet Informatik 2 Thema: Towards Complete Methods for Automatic Complexity and Termination Analysis of (Probabilistic) Programs Abstract: The increasing importance of computer programs in our everyday life has led to more and more complex software systems. To prove correctness of such a system, formal verification is the standard methodology. Two of the most important properties of a program are its termination behavior and its efficiency. Moreover, in recent years randomization in programming has gained a lot of interest. For example, to model non-deterministic behavior in real-world applications, probabilistic concepts have proved very successful. In this talk, we investigate formal verification of programs which also feature assignments via discrete probability distributions. In particular, we are interested in proving (non-)termination and inferring bounds on the (expected) worst-case runtime of such programs. In general, formal verification of programs is undecidable. Still, whenever possible, complete approaches for verifying certain properties on (sub-)classes of programs are preferable to incomplete ones since they always yield definite results, i.e., either a proof or a counterexample. Hence, we also characterize sub-classes of programs for which we can present complete approaches for analyzing termination and runtime complexity. To analyze systems arising from real-world applications, formal verification has to proceed automatically. Thus, we discuss the automation of our results as well. Es laden ein: die Dozentinnen und Dozenten der Informatik -- Marcel Hark Research Group Computer Science 2 RWTH Aachen University Ahornstr. 55 52074 Aachen Germany E-Mail: marcel.hark(a)cs.rwth-aachen.de" Phone: +49-241/80-21218 Fax: +49-241/80-22217 Room: 4208

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Einladung: Informatik-Oberseminar Philipp Wacker
by Philipp Wacker 14 May '21

14 May '21

+********************************************************************** * * * Einladung * * * * Informatik-Oberseminar * * * +********************************************************************** Zeit: Mittwoch, 26. Mai 2021, 14:00 Uhr Zoom: https://rwth.zoom.us/j/92362727123?pwd=MjhBT2VaczI0RDE1c2VNQkxGckw3UT09 <https://rwth.zoom.us/j/92362727123?pwd=MjhBT2VaczI0RDE1c2VNQkxGckw3UT09> Referent: Philipp Wacker, M.Sc. Lehrstuhl Informatik 10 Thema: Interaction Techniques for Mid-Air Pen Input in Handheld Augmented Reality Abstract: Augmented Reality changes the way we interact with virtual information. Currently, virtual information is shown on 2D screens, separated from the real world. With Augmented Reality, virtual content can be shown directly embedded in the real world. This opens up the area of situated modeling in which virtual models are designed in context of the real world to, for example, print them out using a 3D printer. In an initial study, we show that sketching on physical objects improves stroke accuracy compared to strokes on virtual objects, and that features guiding a stroke, either through a concave or convex shape or through a visual guide, further improve the accuracy especially for physical objects. The most available form of Augmented Reality (AR) is Handheld Augmented Reality which shows the virtual information embedded in the camera view of everyday smartphones or tablets. However, continuously specifying a 3D position—needed, e.g., for drawing in mid-air—is not directly possible in today’s systems. We build the ARPen system to allow for situated modeling in Handheld AR, requiring only a 3D-printed pen and a consumer smartphone. But many essential interactions are not yet clear for such a bimanual system. We design and evaluate selection & manipulation techniques to adjust the pose of a mid-air object, as well as menu techniques to control properties of objects in the scene. We show that ray-casting techniques, especially through the tip of the pen, generally perform well. However, interacting on the touchscreen or even combinations of both touchscreen and mid-air input also achieve promising results. To overcome perception issues of determining the depth of virtual objects in Handheld AR, we design depth visualizations that show the position of the pen tip in relation to other objects in the scene. We identify that a heatmap visualization, coloring every object in the scene depending on their distance to the pen tip, achieves best results and was preferred by study participants. We release the ARPen system as an open-source toolbox, enabling researchers to implement and evaluate interaction techniques for Handheld AR with a mid-air pen. Our findings on essential interaction techniques provide a starting point for the development and evaluation of specialized application scenarios. Es laden ein: die Dozentinnen und Dozenten der Informatik

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