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

Einladung: Informatik-Oberseminar Benedikt Brütsch (20. Dez., 16:15 Uhr)

von Benedikt Brütsch

+********************************************************************** * * * Einladung * * * * Informatik-Oberseminar * * * +********************************************************************** Zeit: Donnerstag, 20. Dezember 2018, 16:15 Uhr Ort: Raum 9222, Gebäude E3, Ahornstr. 55 Referent: Dipl.-Inform. Benedikt Brütsch Lehrstuhl Informatik 7 Thema: Strategies in Infinite Games: Structured Reactive Programs and Transducers over Infinite Alphabets Abstract: In this talk, we study the construction of winning strategies in games of the following kind: Two players take turns in choosing symbols from some fixed alphabet. They play forever, thus constructing an infinite sequence of symbols. The winning condition is a set L of such sequences: Player II wins if the constructed sequence is in the set L, otherwise Player I wins. These games can be viewed as a model of reactive systems, which maintain an ongoing interaction with their environment. We consider the so-called synthesis problem: Given a winning condition, determine whether Player II has a winning strategy, and construct such a strategy. First, we study the synthesis of winning strategies in the form of structured reactive programs (for omega-regular winning conditions). In particular, we show an exponential lower bound for the number of (Boolean) program variables that are required in the case of winning conditions specified in linear temporal logic (LTL), roughly matching the known upper bound. Second, we consider a more general form of the synthesis problem, where the alphabet is infinite. Specifically, we focus on the case where the symbols chosen by the players are natural numbers. To represent winning conditions, we define a model of automata over infinite alphabets such as the set N of natural numbers, namely N-memory automata. Analogously, we introduce N-memory transducers to represent strategies. We show that the synthesis problem is solvable in this setting: Given a winning condition defined by a deterministic N-memory automaton with a parity acceptance condition, we can determine which player has a winning strategy and construct such a strategy in the form of a deterministic N-memory transducer. Es laden ein: Die Dozenten der Informatik

5 Jahre, 4 Monate

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Einladung: Informatik-Oberseminar Sarah Winter

von Sarah Winter

+********************************************************************** * * * Einladung * * * * Informatik-Oberseminar * * * +********************************************************************** Zeit: Mittwoch, 19. Dezember 2018, 10:00 Uhr Ort: Gebäude E3, Seminarraum 9222, Ahornstr. 55 Referentin: Sarah Winter, M.Sc. Informatik 7 Thema: Synthesis of Transducers from Relations on Finite Words and Trees Abstract: The synthesis problem asks, given a specification that relates possible inputs to allowed outputs, whether there is a program realizing the specification, and if so, construct one. Such a program is referred to as an implementation of the specification. The field of automata theory offers a rich landscape of models for defining specifications and implementations over both words and trees. We consider synthesis of sequential transducers from automaton-definable specifications on finite words and trees. In this talk, concerning specifications over words, we discuss synthesis of sequential word transducers from rational relations in which the allowed input/output behavior is specified by a given set of synchronizations. Concerning specifications over trees, we focus on synthesis of deterministic top-down tree transducers from tree-automatic specifications. Es laden ein: Die Dozenten der Informatik

5 Jahre, 4 Monate

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Vortrag, heute 16:15, AH I: Prof. Olivier Bonaventure (UC Louvain, BE) "Future Internet Protocols"

von Klaus Wehrle

Liebe Informatiker*innen, ein kurzer Reminder an den Vortrag heute Nachnmittag im Rahmen der Distinguished Lecture Series des SFB 1053 MAKI um 16:15h im AH I. viele Grüße klaus wehrle ************************************************************************ * * * Einladung * * * * Informatik-Kolloquium * * * ************************************************************************ When: Donnerstag, 13. Dezember 2018, 16.15 Uhr Where: AH I, Ahornstr. 55 Referent: Prof. Olivier Bonaventure UCLouvain Title: Future Internet protocols Abstract: For many years, there were few innovations in the core Internet protocols. This changed during the last years with Multipath TCP, IPv6 Segment Routing and protocols such as QUIC. This talk will discuss some of the recent changes to the core Internet protocols and discuss future challenges. Bio: Olivier Bonaventure is Professor at UCLouvain where he leads the IP Networking Lab (https://inl.info.ucl.ac.be). Most of his research focuses on improving Internet protocols. His PhD students participated to the design and implemented several Internet protocols including LISP, Multipath TCP or IPv6 Segment Routing. He wrote the open-source Computer Networking : Principles, Protocols and Practice ebook that is used by various universities and co-founded the Tessares startup that creates innovative solutions based on Multipath TCP.

5 Jahre, 4 Monate

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Guest Talk: Dr. Marc Körner (ICSI, UC Berkeley) "Open Carrier Interfaces as an Enabler for Edge-Supported Services" (Dec 14, 10:00 - 10:45)

von Jens Hiller

************************************************************************ * * * Einladung * * * * Informatik-Kolloquium * * * ************************************************************************ When: Freitag, 14. Dezember 2018, 10.00 Uhr Where: COMSYS Seminar Room (Room 9007), Building E3, Ahornstr. 55 Referent: Dr. Marc Körner International Computer Science Institute (ICSI) and UC Berkeley Netsys Lab group Title: Open Carrier Interfaces as an Enabler for Edge-Supported Services Abstract: Edge computing is an increasingly important theme for carriers and application developers. This talk will outline how a merging of serverless computing and an open-carrier interface can facilitate the growth of edge-supported services. In this model, carriers open up their edge facilities to third-party application providers (hereafter called tenants) by offering the ability to deploy network edge processing on-demand without operator intervention. There are two keys to this Open Carrier Interface (OCI) model. First, the relevant edge processing is only invoked when clients associated with that tenant attach at an edge. Thus, much like serverless computing, the cost of OCI is proportional to the usage, greatly reducing the barriers to deploying new global services. Second, the carrier interface allows the tenant to specify an overall application interaction pattern, which controls where their clients traffic should be directed and provides edge-based lookup and redirection services. The combination of these two features provides a fully-automated and cost-effective way for third-parties to deploy new global services that are enhanced by edge support. Bio: Marc Körner is Postdoctoral Researcher currently working on a DAAD research fellowship at the UC Berkeley Netsys Lab group, the International Computer Science Institute (ICSI), and the EIT Digital Silicon Vally hub. He received a Dr.-Ing. degree from the faculty of EECS at TU Berlin in 2015 for his dissertation on Software Defined Networking based Data Center Services. His research focus is in scope of network technologies and SDN/NFV based data center solutions.

5 Jahre, 4 Monate

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Einladung Informatik-Oberseminar, Ph.D. Exam Public Presentation

von Dan Matheson

+********************************************************************** * * * Einladung * * * * Informatik-Oberseminar * * * +********************************************************************** Zeit: Freitag, 18. Januar 2019, 13.00 Uhr Ort: Raum 9222, Gebäude E 3, Ahornstr. 55 Referent: Dan Matheson, MSCS Lehrstuhl Informatik 3 Thema: SAMEM: A Methodology for the Elicitation and Specification of Requirements for Agile Model-driven Engineering of Large Software Solutions Abstract: In this talk, we present an overview of SAMEM (Software Agile Modeling and Engineering Methodology). The SAMEM focuses on Agile and Model-driven Development (MDD) techniques in the early stages of the product development process, primarily requirements specification. Adaptations and differences in applying Agile and MDD for requirements versus code developed are highlighted. The SAMEM approach has been applied in over 18 industry projects with two different development teams and customers. The SAMEM provides guidance through the abstraction hierarchy from initial ideas to deployment while ensuring engineering due diligence and enabling innovation. Es laden ein: Die Dozenten der Informatik

5 Jahre, 4 Monate

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SFB MAKI Distinguished Lecture: Prof. Olivier Bonaventure (UCLouvain) "Future Internet protocols" (Dez 13, 16:15 - 17:30)

von Oliver Hohlfeld

************************************************************************ * * * Einladung * * * * Informatik-Kolloquium * * * ************************************************************************ When: Donnerstag, 13. Dezember 2018, 16.15 Uhr Where: AH I, Ahornstr. 55 Referent: Prof. Olivier Bonaventure UCLouvain Title: Future Internet protocols Abstract: For many years, there were few innovations in the core Internet protocols. This changed during the last years with Multipath TCP, IPv6 Segment Routing and protocols such as QUIC. This talk will discuss some of the recent changes to the core Internet protocols and discuss future challenges. Bio: Olivier Bonaventure is Professor at UCLouvain where he leads the IP Networking Lab (https://inl.info.ucl.ac.be). Most of his research focuses on improving Internet protocols. His PhD students participated to the design and implemented several Internet protocols including LISP, Multipath TCP or IPv6 Segment Routing. He wrote the open-source Computer Networking : Principles, Protocols and Practice ebook that is used by various universities and co-founded the Tessares startup that creates innovative solutions based on Multipath TCP.

5 Jahre, 4 Monate

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Einladung: Informatik Oberseminar Ulrich Loup

von Ulrich Loup

+********************************************************************** * * * Einladung * * * * Informatik-Oberseminar * * * +********************************************************************** Zeit: Freitag, 14. Dezember 2018, 13:00 Uhr Ort: Gebäude E3, Seminarraum 9222, Ahornstr. 55 Referent: Ulrich Loup Theory of Hybrid Systems Informatik 2 Thema: On Solving Real-algebraic Formulas in a Satisfiability-modulo-theories Framework Abstract: Quantifier-free real-algebraic formulas are Boolean combinations of polynomial equations and inequalities over the domain of the real numbers. Coming with a strong expressiveness and a still decidable satisfiability problem, real- algebraic formulas are a precious modeling language in many academic, industrial and commercial areas. However, only some classes of real-algebraic formulas allow an efficient solving in practice. For instance, conjunctions of linear real-algebraic constraints can be solved with the very successful simplex method. The general quantifier-free real-algebraic satisfiability problem, however, has a worst-case time complexity bound which is exponential in the number of input variables. Methods solving this general problem directly are often inefficient in practice. The very popular cylindrical algebraic decomposition (CAD) method has a doubly-exponential complexity bound in the number of input variables for its search space. This thesis tackles the solving of general quantifier-free real-algebraic formulas with a combination of different methods in a satisfiability-modulo- theories (SMT) framework: A SAT solver computes partial assignments for the Boolean structure of the real-algebraic formula and real-algebraic solvers check these assignments for consistency in the real domain. If the assignment is infeasible in the real domain, the SAT solver would profit from a small - preferably minimal - reason for this conflict in terms of a subset of the constraints corresponding to the conflicting assignment. In this talk, I focus on two real-algebraic solvers in our SMT-solving framework SMT-RAT, which are major contributions of my thesis. The first solver is an implementation of the CAD method specialized for an efficient embedding into an SMT solver. In particular, the CAD method is extended by the ability to solve incrementally, i.e. reuse pre-computed results, to backtrack and to compute minimal reasons. Moreover, bounds to the variables are used to prune the CAD search space, especially when combining the method with interval-arithmetic techniques. The second solver uses an extension of Buchberger's algorithm in order to compute a Gröbner basis. The solver supports incremental solving, backtracking and minimal reasons for some unsatisfiable cases, as well. We extended the method so that the solver can also be used in order to simplify formulas for other real-algebraic solvers in the SMT-solving framework. As a main part, my thesis comprises an evaluation of the two solvers in the SMT-RAT framework. In particular, the effects of combining the CAD method with a Gröbner-bases solver in an SMT framework are investigated. In my talk, some experimental results of this evaluation are shown, too.

5 Jahre, 5 Monate

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Einladung: Informatik Oberseminar Florian Frohn

von Florian Frohn

+********************************************************************** * * * Einladung * * * * Informatik-Oberseminar * * * +********************************************************************** Zeit: Dienstag, 11. Dezember 2018, 16:15 Uhr Ort: Gebäude E3, Seminarraum 9222, Ahornstr. 55 Referent: Florian Frohn, M.Sc. Lehr- und Forschungsgebiet Informatik 2 Thema: Automated Complexity Analysis of Rewrite Systems Abstract: Besides functional correctness, one of the most important prerequisites for the success of software is efficiency: The desired results need to be computed not only correctly, but also in time. Thus, analyzing the runtime complexity of software is indispensable in practice. Unfortunately, analyzing the complexity of large programs manually is infeasible. Hence, automated complexity analysis techniques are needed. In this way, performance pitfalls can be highlighted automatically like other bugs which can nowadays be found by compilers or static analyzers. However, statically analyzing the complexity of real-world programs poses several problems. For example, most programming languages lack formal semantics. Moreover, different programming languages offer different features, so static analyses for one language do not necessarily apply to others. A common solution for these problems is to transform programs into low-level formalisms like integer or term rewrite systems that can be analyzed without worrying about language-specific peculiarities. State-of-the-art tools that analyze the worst-case complexity of rewrite systems are restricted to the inference of upper bounds. In this talk, the first techniques for the inference of lower bounds on the worst-case complexity of integer and term rewrite systems are introduced. While upper bounds can prove the absence of performance-critical bugs, lower bounds can be used to find them. For term rewriting, the power of the presented technique gives rise to the question whether the existence of a non-constant lower bound is decidable. Thus, the corresponding decidability results are also discussed in this talk. Es laden ein: Die Dozenten der Informatik

5 Jahre, 5 Monate

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Einladung: Informatik Oberseminar Markus Towara

von Markus Towara

+********************************************************************** * * * Einladung * * * * Informatik-Oberseminar * * * +********************************************************************** Zeit: Freitag, 7. Dezember 2018, 10.00 Uhr Ort: IT Center Seminarraum 004, Kopernikusstr. 6 Referent: Dipl.-Ing. Markus Towara Informatik 12: Software and Tools for Computational Engineering Thema: Discrete Adjoint Optimization with OpenFOAM Abstract: Computer simulations and computer aided design in the past decades have evolved into a valuable instrument, penetrating just about every branch of engineering in industry and academia. More specifically, computational fluid dynamics (CFD) simulations allow to inspect flow phenomena in a variety of applications. As simulation methods evolve, mature, and are adopted by a rising number of users, the demand for methods which not only predict the result of a specific configuration, but can give indications on how to improve the design, increases. This thesis is concerned with the efficient calculation of sensitivity information of CFD algorithms, and their application to numerical optimization. The sensitivities are obtained by applying Algorithmic Differentiation (AD). A specific emphasis of this thesis is placed on the efficient application of adjoint methods, including parallelism, for commonly used CFD finite volume methods (FVM) and their implementation in the open source framework OpenFOAM. Es laden ein: Die Dozenten der Informatik

5 Jahre, 5 Monate

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Einladung: Informatik-Oberseminar Arham Muslim

von Bombelka, Angelika

** Terminänderung ** ************************************************************************ * * Einladung * * * Informatik-Oberseminar * * ************************************************************************ Zeit: Freitag, 14.12.2018, 10.00 Uhr Ort: Gebäude E3, Seminarraum 9222, Ahornstr. 55 Referent: Herr Arham Muslim, M.Sc. Titel: OpenLAP: A User-Centered Open Learning Analytics Platform Abstract: During the last few years, Learning Analytics (LA) has gained the interest of researchers in the field of Technology Enhanced Learning (TEL). Generally, LA deals with the development of methods that harness educational data sets to support the learning process. It shares a movement from data to analysis to action to learning. Recently, the demand for self-organized, networked, and lifelong learning opportunities has increased. Therefore, there is a need to provide an understanding of how different learners learn in these open learning settings and how learners, educators, institutions, and researchers can best support this process. Moreover, this openness should be reflected in the conceptualization and development of innovative LA approaches in order to achieve more effective learning experiences. Open Learning Analytics (OLA) is an emerging research field that has the potential to deal with these challenges in open learning environments. However, the concrete solutions and implementations that can deliver an effective and efficient OLA are still lacking. Most solutions currently available does not continuously involve end-users in the LA process and follow design patterns which make it difficult to adopt new user requirements. Furthermore, the available implementations are designed and developed for specific scenarios, which address the requirements of a specific set of stakeholders by relying on a predefined set of questions and indicators. These limitations restrict the scope of such solutions and implementations in the context of OLA targeting various stakeholders with different needs. The aim of this dissertation is to introduce personalization in the LA process by investigating the design of an effective user-centered Open Learning Analytics Platform (OpenLAP) and providing its conceptual, implementation, and evaluation details. OpenLAP provides a user-friendly interface that supports an interactive, exploratory, and real-time user experience to allow the end-users to dynamically define new indicators that meet their goals. Moreover, OpenLAP is designed to be modular and extensible allowing easy integration of new data sources, analytics methods, and visualization techniques at runtime to adopt the new requirements of multiple stakeholders and deliver an ecosystem for OLA. The main contributions of this dissertation include (1) a comprehensive analysis of the currently available LA tools and solutions with respect to their support for openness and personalization, (2) a theoretically sound design of a user-centered OpenLAP based on the requirements gathered from the empirical analysis of the literature, (3) a concrete implementation of OpenLAP providing an interface to self-define the indicators and an extensible mechanism to easily integrated new data sources, analytics methods, and visualization techniques, and (4) a thorough evaluation of OpenLAP in a pilot study at RWTH Aachen University to assess it in terms of usability, usefulness, extensibility, and modularity. Es laden ein: Die Dozenten der Informatik Lehr- und Forschungsgebiet Informatik 9

5 Jahre, 5 Monate

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