Infoscience
(66.951 recursos)
Repository of the publications, research reports, PhD Theses, Ms Theses, semester works, lectures, etc., of the Facultés, Laboratories and Researchers at the EPFL.
Mostrando recursos 1 - 20 de 444
1.
A Conceptual View on Trajectories - Vangenot, Christelle; Porto, Fabio; de Macedo, Jose Antonio; Damiani, Maria Luisa; Parent, Christine; Spaccapietra, Stefano
Analysis of trajectory data is the key to a growing number of applications aiming at global understanding and management of complex phenomena that involve moving objects (e.g. worldwide courier distribution, city traffic management, bird migration monitoring). Current DBMS support for such data is limited to the ability to store and query raw movement (i.e. the spatio-temporal position of an object). This paper explores how conceptual modeling could provide applications with direct support of trajectories (i.e. movement data that is structured into countable semantic units) as a first class concept. A specific concern is to allow enriching trajectories with semantic annotations...
2.
Rank Distance Codes for ISI channels - Calderbank, A. R.; Diggavi, S. N.; Dusad, S.
Designs for transmit alphabet constrained space-time codes naturally lead to questions about the design of rank distance codes. Recently, diversity embedded multi-level space-time codes for flat fading channels have been designed by using sets of binary matrices with rank distance guarantees over the binary field and mapping them onto QAM and PSK constellations. In this paper we give the design of diversity embedded space-time codes for fading Inter-Symbol Interference (ISI) channels with provable rank distance guarantees. In the process of doing so we also get a (asymptotic) characterization of the rate-diversity trade-off for multiple antenna fading ISI channels. The key...
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A Symbolic Characterisation of Open Bisimulation for the Spi Calculus - Briais, Sébastien
Open hedged bisimulation was proposed as a generalisation to the spi calculus of the pi calculus'open bisimulation. In this paper, we extend previous work on open hedged bisimulation. We show that open hedged bisimilarity is closed under respectful substitutions and give a symbolic characterisation of open hedged bisimulation. The latter result is an important step towards mechanisation of open hedged bisimilarity.
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Energy conversion processes for the use of geothermal heat - Final report - Girardin, Luc; Ramsel, Kathrin; Schädle, Karl-Heinz; Ködel, Joachim; Marechal, François; Minder, Rudolf
The study deals with theoretical as well as with practical aspects of the conversion of geothermal heat to electricity. The report is divided into three parts: Part I: General study Part II: Practical experience: planning & operation of geothermal power plants Part III: Methodology for the optimal integration of energy conversion system in geothermal power plants. In the first part the specific properties and characteristics of geothermal resources as heat sources are discussed. Both, EGS as well as deep aquifer resources are considered. Furthermore a general survey of conversion processes is presented with special emphasis on thermo-electric...
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Multi-level System Modeling Using the Foundation Concepts of RM-ODP - Wood, Bryan; Lê, Lam-Son; Wegmann, Alain
A specification in Enterprise Architecture (EA) requires the modeling of an enterprise across multiple levels, from the markets in which it operates down to the implementation of the IT systems that support its operations. Our goal is the development of a method and of a CAD tool that support such modeling. To achieve our goal, we need an ontology to represent systematically all the systems at the multiple levels identified in an enterprise. We base our ontology on the foundation modeling concepts defined in Part 2 of ISO/ITU Standard "Reference Model of Open Distributed Processing" (RM-ODP). In this paper, we...
6.
Extending OWL with Explicit Dependency - Porto, Fabio; Calbimonte, Jean_Paul
Functional Dependency has been extensively studied in database theory. It provides an elegant formalism for specifying key constraints and is the basis for normalization theory used in Relational database design. Given its known axiomatization through logical implications it is expected that the ontology community would be interested in investigating its applicability to conceptual modeling. This paper investigates the extension of OWL ontologies with functional dependencies. In particular, we focus on key dependency and a new class referred to as explicit dependency. The latter is a functional dependency in which the function that correlates the left-hand side to the right-hand side...
Degree of synchrony and failure model are two independent parameters that determine a particular type of system.
The notion of faulty component is helpful and even necessary for the analysis of distributed computations when failures occur.
In this work, we question these two basic principles of fault-tolerant distributed computing, and show that it is both possible and worthy to renounce them in the context of benign failures: we present a computational model, suitable for systems with benign...
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Integration of ISS into the VIOLA Meta-scheduling Environment - Ziegler, Wolfgang; Wieder, Philipp; Wäldrich, Oliver; Tran, Trach-Minh; Spada, Michela; Sawley, Marie-Christine; Nellari, Nello; Maffioletti, Sergio; Kuonen, Pierre; Keller, Vincent; Gruber, Ralf; Cristiano, Kevin
The authors present the integration of the Intelligent (Grid) Scheduling System into the VIOLA meta-scheduling environment which itself is based on the UNICORE Grid software. The goal of the new, integrated environment is to enable the submission of jobs to the Grid system best-suited for the application workflow. For this purpose a cost function is used that exploits information about the type of application, the characteristics of the system architectures, as well as the availabilities of the resources. This document presents an active collaboration between Ecole Polytechnique Fédérale de Lausanne (EPFL), Ecole d'Ingénieurs et d'Architectes (EIF) de Fribourg, Forschungszentrum Jülich,...
9.
Appliation-oriented sheduling for HPC Grids - Witzig, Christoph; Sawley, Marie-Christine; Maffioletti, Sergio; Kunszt, Peter; Yahyapour, Ramin; Schwiegelshohn, Uwe; Manneback, Pierre; Ziegler, Wolfgang; Wäldrich, Oliver; Wieder, Philipp; Kuonen, Pierre; Cristiano, Kevin; Tran, Trach-Minh; Tolou, Ali; Thiémard, Michela; Keller, Vincent; Gruber, Ralf; Drotz, Alain
The Intelligent Grid Scheduling Service (ISS) aims at finding an optimally suited computational resource for a given application component. An objective cost model function is used to decide it. It includes information on a parametrization of the components and the machines in a Grid, and on the availability of the clusters. The paper presents a detailed formulation of the environment and outlines the integration of the ISS model into the UNICORE-based VIOLA meta-scheduling Grid middleware. This document is an active collaboration between EPFL, EIA-FR, Forschungszentrum Jülich, Fraunhofer Gesellschaft, University of Dortmund, CETIC, CSCS, and Switch.
10.
Digital Libraries - Nguyen, T Q
Digital libraries are libraries in which collections are stored in a digital format (the metadata at least). Digital libraries are now being made publicly available. However, building good user interfaces to query heterogeneous libraries requires to have a good knowledge on the type of available information (e.g. which attributes are useful for filtering). In this project, we harvest (using the Z39.50 and OAI-PMH protocol) and analyze (in terms of useful attributes for querying) four important digital libraries: Nebis (five million items), Infoscience (sixty thousand items), CiteSeer (seven hundred thousand items) and The European Library (one and a half million items).
11.
Semantic-aware Obfuscation for Location Privacy - Bertino, Elisa; Silvestri, Claudio; Damiani, Maria Luisa
In this paper we present a novel approach to location obfuscation for location privacy purposes. The motivating observation is that obfuscation strategies only grounded on geometric criteria can lead to privacy leaks. We thus propose to complement geometry-based approaches with obfuscation methods which account of the semantic context in which users are located. The unique contribution of the paper is the introduction of a comprehensive obfuscation framework consisting of a semantic-aware obfuscation model and a novel algorithm for the generation of obfuscated spaces of which we report an experimental evaluation.
12.
Patents and development in the knowledge economy - Foray, Dominique
This document refers to the relevance of IP in the knowledge economy, explaining the importance of the rapid dissemination of new and superior knowledge. However, we point out that rapid dissemination can be the enemy of innovation. In this context, we explain that the patent system has many virtues as an incentive to future inventors. However, by recognising exclusive rights, the patent restricts de facto the use of knowledge and its exploitation. Patents and other intellectual property rights (IPRs) are by no means the only solution to the problem of supporting inventors in their effort to capture benefits stemming from...
13.
Bottleneck Discovery and Overlay Management in Network Coded Peer-to-Peer Systems - Gkantsidis, C.; Diggavi, S.; Fragouli, C.; Jafarisiavoshani, M.
The performance of peer-to-peer (P2P) networks depends critically on the good connectivity of the overlay topology. In this paper we study P2P networks for content distribution (such as Avalanche) that use randomized network coding techniques. The basic idea of such systems is that peers randomly combine and exchange linear combinations of the source packets. A header appended to each packet specifes the linear combination that the packet carries. In this paper we show that the linear combinations a node receives from its neighbors reveal structural information about the network. We propose algorithms to utilize this observation for topology management to...
14.
Translation Correctness for First-Order Object-Oriented Pattern Matching - Odersky, Martin; Ma, Qin; Emir, Burak
Pattern matching makes ML programs more concise and readable, and these qualities are also sought in object-oriented settings. However, objects and classes come with open class hierarchies, extensibility requirements and the need for data abstraction, which all conflict with matching on concrete data types. Extractor-based pattern matching has been proposed to address this conflict. Extractors are user-defined methods that perform the task of value discrimination and deconstruction during pattern matching. In this paper, we give the first formalization of extractor-based matching, using a first-order object-oriented calculus. We give a direct operational semantics and prove it sound. We then present an...
15.
Side-information Scalable Source Coding - Diggavi, Suhas; Tian, Chao
The problem of side-information scalable source coding is considered in this work, where the encoder constructs a progressive description, such that the receiver with high quality side information will be able to truncate the bitstream and reconstruct in the rate distortion sense, while the receiver with low quality side information will have to receive further data in order to decode. We provide inner and outer bounds for general discrete sources. The achievable region is shown to be tight for the case that either of the stages requires a lossless reconstruction. Furthermore we show that the gap between the achievable region...
16.
Collective search of a single odour source using cooperation - Faltings, Boi; Leaute, Thomas; Lochmatter, Thomas; Petcu, Adrian; Herrmann, Alexandre
We study coordination strategies for a multirobot team. The goal is to find the source of an odour most efficiently in terms of the distance travelled by the robots and the time required to discover the source. We focus on the problem of finding the source of the odour once a robot has already found the plume of this odour. The results show that the studied algorithms are effective in non-homogeneous wind models, which include turbulences.
17.
Adaptive and Distributed Speed Limitation in a Simulation of the Swiss Highway Network - Faltings, Boi; Leaute, Thomas; Schumacher, Michael; Petcu, Adrian; Rey, Charles-Francois
The present work is aimed at finding a decentralized, adaptive solution for intelligent speed limitation that increases highway efficiency. Each segment of the highway is associated with an intelligent agent which can monitor traffic conditions and impose speed limits. Agents communicate with neighbouring agents to exchange information and effectively coordinate their speed limitations they impose. We propose to use the Distributed Constraint Optimisation framework to model the coordination problem, and the DPOP algorithm for solving it.
18.
Geometry-based scene representation with distributed vision sensors. - Frossard, P.; Tosic, I.
This paper addresses the problem of efficient representation and compression of scenes captured by distributed vision sensors. We propose a novel geometrical model to describe the correlation between different views of a three-dimensional scene. We first approximate the camera images by sparse expansion over a dictionary of geometric atoms, as the most important visual features are likely to be equivalently dominant in images from multiple cameras. The correlation model is then built on local geometrical transformations between corresponding features taken in different views, where correspondences are defined based on shape and epipolar geometry constraints. Based on this geometrical framework, we...
19.
Extending Peer-to-Peer Networks for Approximate Search - Faltings, Boi; Schmidt, Roman; Schumacher, Michael; Mowat, Alain
Peer-to-Peer (P2P) networks are used worldwide for many applications such as file sharing or news servers. There are many different implementations available, each with its pros and cons. In this paper, we propose a way to enable approximate queries in a P2P network by using a special encoding function and error correcting codes. The encoding function maintains neighborhood relationships so that two similar inputs will result in two similar outputs. The error correcting code is then used to group the similar encoded values around special codewords. In this manner, similar content is located as close as possible in the network....
20.
Secure Neighbor Discovery in Wireless Networks: Is It Possible? - Hubaux, Jean-Pierre; Papadimitratos, Panos; Poturalski, Marcin
Wireless communication enables a broad spectrum of applications, ranging from commodity to tactical systems. Neighbor discovery (ND), that is, determining which devices are within direct radio communication, is a building block of network protocols and applications, and its vulnerability can severely compromise their functionalities. A number of proposals to secure neighbor discovery have been published, but none have analyzed the problem formally. In this paper, we contribute such an analysis: we build a formal model capturing salient characteristics of wireless systems, most notably obstacles and interference, and we provide a specification of the ND problem. Then, we derive an impossibility...
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