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537 results on '"Tzitzikas, Yannis"'

58. Extending Faceted Search with Automated Object Ranking

Author

Manioudakis, Kostas, Tzitzikas, Yannis, Barbosa, Simone Diniz Junqueira, Editorial Board Member, Filipe, Joaquim, Editorial Board Member, Ghosh, Ashish, Editorial Board Member, Kotenko, Igor, Editorial Board Member, Zhou, Lizhu, Editorial Board Member, Garoufallou, Emmanouel, editor, Fallucchi, Francesca, editor, and William De Luca, Ernesto, editor

Published
2019
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59. Knowledge Graph Embeddings over Hundreds of Linked Datasets

Author

Mountantonakis, Michalis, Tzitzikas, Yannis, Barbosa, Simone Diniz Junqueira, Editorial Board Member, Filipe, Joaquim, Editorial Board Member, Ghosh, Ashish, Editorial Board Member, Kotenko, Igor, Editorial Board Member, Zhou, Lizhu, Editorial Board Member, Garoufallou, Emmanouel, editor, Fallucchi, Francesca, editor, and William De Luca, Ernesto, editor

Published
2019
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60. Methods and Tools for Supporting the Integration of Stocks and Fisheries

Author

Tzitzikas, Yannis, Marketakis, Yannis, Minadakis, Nikos, Mountantonakis, Michalis, Candela, Leonardo, Mangiacrapa, Francesco, Pagano, Pasquale, Perciante, Costantino, Castelli, Donatella, Taconet, Marc, Gentile, Aureliano, Gorelli, Giulia, Barbosa, Simone Diniz Junqueira, Series Editor, Filipe, Joaquim, Series Editor, Kotenko, Igor, Series Editor, Washio, Takashi, Series Editor, Yuan, Junsong, Series Editor, Zhou, Lizhu, Series Editor, Ghosh, Ashish, Series Editor, Salampasis, Michail, editor, and Bournaris, Thomas, editor

Published
2019
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61. Crowd-Sourced Collection of Task-Oriented Human-Human Dialogues in a Multi-domain Scenario

Author

Braunschweiler, Norbert, Papadakos, Panagiotis, Kotti, Margarita, Marketakis, Yannis, Tzitzikas, Yannis, Goos, Gerhard, Founding Editor, Hartmanis, Juris, Founding Editor, Bertino, Elisa, Editorial Board Member, Gao, Wen, Editorial Board Member, Steffen, Bernhard, Editorial Board Member, Woeginger, Gerhard, Editorial Board Member, Yung, Moti, Editorial Board Member, and Ekštein, Kamil, editor

Published
2019
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62. A Simple Method to Produce Algorithmic MIDI Music based on Randomness, Simple Probabilities and Multi-Threading

Author

Tzitzikas, Yannis

Subjects
Computer Science - Sound
Abstract

This paper introduces a simple method for producing multichannel MIDI music that is based on randomness and simple probabilities. One distinctive feature of the method is that it produces and sends in parallel to the sound card more than one unsynchronized channels by exploiting the multi-threading capabilities of general purpose programming languages. As consequence the derived sound offers a quite ``full" and ``unpredictable" acoustic experience to the listener. Subsequently the paper reports the results of an evaluation with users. The results were very surprising: the majority of users responded that they could tolerate this music in various occasions., Comment: 7 pages, 5 figures

Published
2013

63. Information Carriers and Identification of Information Objects: An Ontological Approach

Author

Doerr, Martin and Tzitzikas, Yannis

Subjects
Computer Science - Digital Libraries
Abstract

Even though library and archival practice, as well as Digital Preservation, have a long tradition in identifying information objects, the question of their precise identity under change of carrier or migration is still a riddle to science. The objective of this paper is to provide criteria for the unique identification of some important kinds of information objects, independent from the kind of carrier or specific encoding. Our approach is based on the idea that the substance of some kinds of information objects can completely be described in terms of discrete arrangements of finite numbers of known kinds of symbols, such as those implied by style guides for scientific journal submissions. Our theory is also useful for selecting or describing what has to be preserved. This is a fundamental problem since curators and archivists would like to formally record the decisions of what has to be preserved over time and to decide (or verify) whether a migration (transformation) preserves the intended information content. Furthermore, it is important for reasoning about the authenticity of digital objects, as well as for reducing the cost of digital preservation., Comment: 30 pages, 10 figures. Comparison to the previous version: Improved use of language

Published
2012

64. Query processing in distributed, taxonomy-based information sources

Author

Meghini, Carlo, Tzitzikas, Yannis, Coltella, Veronica, and Analyti, Anastasia

Subjects
Computer Science - Distributed, Parallel, and Cluster Computing, Computer Science - Databases
Abstract

We address the problem of answering queries over a distributed information system, storing objects indexed by terms organized in a taxonomy. The taxonomy consists of subsumption relationships between negation-free DNF formulas on terms and negation-free conjunctions of terms. In the first part of the paper, we consider the centralized case, deriving a hypergraph-based algorithm that is efficient in data complexity. In the second part of the paper, we consider the distributed case, presenting alternative ways implementing the centralized algorithm. These ways descend from two basic criteria: direct vs. query re-writing evaluation, and centralized vs. distributed data or taxonomy allocation. Combinations of these criteria allow to cover a wide spectrum of architectures, ranging from client-server to peer-to-peer. We evaluate the performance of the various architectures by simulation on a network with O(10^4) nodes, and derive final results. An extensive review of the relevant literature is finally included.

Published
2011

65. Similarity-based Browsing over Linked Open Data

Author

Hickson, Michael, Kargakis, Yannis, and Tzitzikas, Yannis

Subjects
Computer Science - Digital Libraries
Abstract

An increasing amount of data is published on the Web according to the Linked Open Data (LOD) principles. End users would like to browse these data in a flexible manner. In this paper we focus on similarity-based browsing and we introduce a novel method for computing the similarity between two entities of a given RDF/S graph. The distinctive characteristics of the proposed metric is that it is generic (it can be used to compare nodes of any kind), it takes into account the neighborhoods of the nodes, and it is configurable (with respect to the accuracy vs computational complexity tradeoff). We demonstrate the behavior of the metric using examples from an application over LOD. Finally, we generalize and elaborate on implementation approaches harmonized with the distributed nature of LOD which can be used for computing the most similar entities using neighborhood-based similarity metrics.

Published
2011

66. Object-Relational Database Representations for Text Indexing

Author

Papadakos, Panagiotis, Theoharis, Yannis, Marketakis, Yannis, Armenatzoglou, Nikos, and Tzitzikas, Yannis

Subjects
Computer Science - Information Retrieval, Computer Science - Databases
Abstract

One of the distinctive features of Information Retrieval systems comparing to Database Management systems, is that they offer better compression for posting lists, resulting in better I/O performance and thus faster query evaluation. In this paper, we introduce database representations of the index that reduce the size (and thus the disk I/Os) of the posting lists. This is not achieved by redesigning the DBMS, but by exploiting the non 1NF features that existing Object-Relational DBM systems (ORDBMS) already offer. Specifically, four different database representations are described and detailed experimental results for one million pages are reported. Three of these representations are one order of magnitude more space efficient and faster (in query evaluation) than the plain relational representation.

Published
2009

67. Epilogue

Author

Tzitzikas, Yannis, Marketakis, Yannis, Tzitzikas, Yannis, and Marketakis, Yannis

Published
2018
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72. The Anatomy of Mitos Web Search Engine

Author

Papadakos, Panagiotis, Vasiliadis, Giorgos, Theoharis, Yannis, Armenatzoglou, Nikos, Kopidaki, Stella, Marketakis, Yannis, Daskalakis, Manos, Karamaroudis, Kostas, Linardakis, Giorgos, Makrydakis, Giannis, Papathanasiou, Vangelis, Sardis, Lefteris, Tsialiamanis, Petros, Troullinou, Georgia, Vandikas, Kostas, Velegrakis, Dimitris, and Tzitzikas, Yannis

Subjects
Computer Science - Information Retrieval
Abstract

Engineering a Web search engine offering effective and efficient information retrieval is a challenging task. This document presents our experiences from designing and developing a Web search engine offering a wide spectrum of functionalities and we report some interesting experimental results. A rather peculiar design choice of the engine is that its index is based on a DBMS, while some of the distinctive functionalities that are offered include advanced Greek language stemming, real time result clustering, and advanced link analysis techniques (also for spam page detection).

Published
2008

73. Query Evaluation in P2P Systems of Taxonomy-based Sources: Algorithms, Complexity, and Optimizations

Author

Meghini, Carlo, Tzitzikas, Yannis, and Analyti, Anastasia

Subjects
Computer Science - Databases, Computer Science - Distributed, Parallel, and Cluster Computing, Computer Science - Data Structures and Algorithms, Computer Science - Logic in Computer Science
Abstract

In this study, we address the problem of answering queries over a peer-to-peer system of taxonomy-based sources. A taxonomy states subsumption relationships between negation-free DNF formulas on terms and negation-free conjunctions of terms. To the end of laying the foundations of our study, we first consider the centralized case, deriving the complexity of the decision problem and of query evaluation. We conclude by presenting an algorithm that is efficient in data complexity and is based on hypergraphs. More expressive forms of taxonomies are also investigated, which however lead to intractability. We then move to the distributed case, and introduce a logical model of a network of taxonomy-based sources. On such network, a distributed version of the centralized algorithm is then presented, based on a message passing paradigm, and its correctness is proved. We finally discuss optimization issues, and relate our work to the literature.

Published
2007

74. PFSgeo: Preference-Enriched Faceted Search for Geographical Data

Author

Lionakis, Panagiotis, Tzitzikas, Yannis, Hutchison, David, Series editor, Kanade, Takeo, Series editor, Kittler, Josef, Series editor, Kleinberg, Jon M., Series editor, Mattern, Friedemann, Series editor, Mitchell, John C., Series editor, Naor, Moni, Series editor, Pandu Rangan, C., Series editor, Steffen, Bernhard, Series editor, Terzopoulos, Demetri, Series editor, Tygar, Doug, Series editor, Weikum, Gerhard, Series editor, Panetto, Hervé, editor, Debruyne, Christophe, editor, Gaaloul, Walid, editor, Papazoglou, Mike, editor, Paschke, Adrian, editor, Ardagna, Claudio Agostino, editor, and Meersman, Robert, editor

Published
2017
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75. How Linked Data can Aid Machine Learning-Based Tasks

Author

Mountantonakis, Michalis, Tzitzikas, Yannis, Hutchison, David, Series editor, Kanade, Takeo, Series editor, Kittler, Josef, Series editor, Kleinberg, Jon M., Series editor, Mattern, Friedemann, Series editor, Mitchell, John C., Series editor, Naor, Moni, Series editor, Pandu Rangan, C., Series editor, Steffen, Bernhard, Series editor, Terzopoulos, Demetri, Series editor, Tygar, Doug, Series editor, Weikum, Gerhard, Series editor, Kamps, Jaap, editor, Tsakonas, Giannis, editor, Manolopoulos, Yannis, editor, Iliadis, Lazaros, editor, and Karydis, Ioannis, editor

Published
2017
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80. Querying the Web of Data with SPARQL-LD

Author

Fafalios, Pavlos, Yannakis, Thanos, Tzitzikas, Yannis, Hutchison, David, Series editor, Kanade, Takeo, Series editor, Kittler, Josef, Series editor, Kleinberg, Jon M., Series editor, Mattern, Friedemann, Series editor, Mitchell, John C., Series editor, Naor, Moni, Series editor, Pandu Rangan, C., Series editor, Steffen, Bernhard, Series editor, Terzopoulos, Demetri, Series editor, Tygar, Doug, Series editor, Weikum, Gerhard, Series editor, Fuhr, Norbert, editor, Kovács, László, editor, Risse, Thomas, editor, and Nejdl, Wolfgang, editor

Published
2016
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83. Species Identification Through Preference-Enriched Faceted Search

Author

Tzitzikas, Yannis, Bailly, Nicolas, Papadakos, Panagiotis, Minadakis, Nikos, Nikitakis, George, Diniz Junqueira Barbosa, Simone, Series editor, Chen, Phoebe, Series editor, Du, Xiaoyong, Series editor, Filipe, Joaquim, Series editor, Kotenko, Igor, Series editor, Liu, Ting, Series editor, Sivalingam, Krishna M., Series editor, Washio, Takashi, Series editor, Garoufallou, Emmanouel, editor, Hartley, Richard J., editor, and Gaitanou, Panorea, editor

Published
2015
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84. System Implementation

Author

Sacco, Giovanni Maria, Tzitzikas, Yannis, Ferré, Sébastien, Sacco, Giovanni Maria, editor, and Tzitzikas, Yannis, editor

Published
2009
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93. Exploratory Professional Search through Semantic Post-Analysis of Search Results

Author

Fafalios, Pavlos, Tzitzikas, Yannis, Hutchison, David, Series editor, Kanade, Takeo, Series editor, Kittler, Josef, Series editor, Kleinberg, Jon M., Series editor, Kobsa, Alfred, Series editor, Mattern, Friedemann, Series editor, Mitchell, John C., Series editor, Naor, Moni, Series editor, Nierstrasz, Oscar, Series editor, Pandu Rangan, C., Series editor, Steffen, Bernhard, Series editor, Terzopoulos, Demetri, Series editor, Tygar, Doug, Series editor, Weikum, Gerhard, Series editor, Paltoglou, Georgios, editor, Loizides, Fernando, editor, and Hansen, Preben, editor

Published
2014
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94. Generating Synthetic RDF Data with Connected Blank Nodes for Benchmarking

Author

Lantzaki, Christina, Yannakis, Thanos, Tzitzikas, Yannis, Analyti, Anastasia, Hutchison, David, editor, Kanade, Takeo, editor, Kittler, Josef, editor, Kleinberg, Jon M., editor, Kobsa, Alfred, editor, Mattern, Friedemann, editor, Mitchell, John C., editor, Naor, Moni, editor, Nierstrasz, Oscar, editor, Pandu Rangan, C., editor, Steffen, Bernhard, editor, Terzopoulos, Demetri, editor, Tygar, Doug, editor, Weikum, Gerhard, editor, Presutti, Valentina, editor, d’Amato, Claudia, editor, Gandon, Fabien, editor, d’Aquin, Mathieu, editor, Staab, Steffen, editor, and Tordai, Anna, editor

Published
2014
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95. MatWare : Constructing and Exploiting Domain Specific Warehouses by Aggregating Semantic Data

Author

Tzitzikas, Yannis, Minadakis, Nikos, Marketakis, Yannis, Fafalios, Pavlos, Allocca, Carlo, Mountantonakis, Michalis, Zidianaki, Ioanna, Hutchison, David, editor, Kanade, Takeo, editor, Kittler, Josef, editor, Kleinberg, Jon M., editor, Kobsa, Alfred, editor, Mattern, Friedemann, editor, Mitchell, John C., editor, Naor, Moni, editor, Nierstrasz, Oscar, editor, Pandu Rangan, C., editor, Steffen, Bernhard, editor, Terzopoulos, Demetri, editor, Tygar, Doug, editor, Weikum, Gerhard, editor, Presutti, Valentina, editor, d’Amato, Claudia, editor, Gandon, Fabien, editor, d’Aquin, Mathieu, editor, Staab, Steffen, editor, and Tordai, Anna, editor

Published
2014
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97. Blank Node Matching and RDF/S Comparison Functions

Author

Tzitzikas, Yannis, Lantzaki, Christina, Zeginis, Dimitris, Hutchison, David, editor, Kanade, Takeo, editor, Kittler, Josef, editor, Kleinberg, Jon M., editor, Mattern, Friedemann, editor, Mitchell, John C., editor, Naor, Moni, editor, Nierstrasz, Oscar, editor, Pandu Rangan, C., editor, Steffen, Bernhard, editor, Sudan, Madhu, editor, Terzopoulos, Demetri, editor, Tygar, Doug, editor, Vardi, Moshe Y., editor, Weikum, Gerhard, editor, Cudré-Mauroux, Philippe, editor, Heflin, Jeff, editor, Sirin, Evren, editor, Tudorache, Tania, editor, Euzenat, Jérôme, editor, Hauswirth, Manfred, editor, Parreira, Josiane Xavier, editor, Hendler, Jim, editor, Schreiber, Guus, editor, Bernstein, Abraham, editor, and Blomqvist, Eva, editor

Published
2012
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98. An Interactive Exploratory System with Real-Time Preference Elicitation

Author

Papadakos, Panagiotis, Tzitzikas, Yannis, Zafeiri, Dafni, Hutchison, David, editor, Kanade, Takeo, editor, Kittler, Josef, editor, Kleinberg, Jon M., editor, Mattern, Friedemann, editor, Mitchell, John C., editor, Naor, Moni, editor, Nierstrasz, Oscar, editor, Pandu Rangan, C., editor, Steffen, Bernhard, editor, Sudan, Madhu, editor, Terzopoulos, Demetri, editor, Tygar, Doug, editor, Vardi, Moshe Y., editor, Weikum, Gerhard, editor, Wang, X. Sean, editor, Cruz, Isabel, editor, Delis, Alex, editor, and Huang, Guangyan, editor

Published
2012
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99. Web Searching with Entity Mining at Query Time

Author

Fafalios, Pavlos, Kitsos, Ioannis, Marketakis, Yannis, Baldassarre, Claudio, Salampasis, Michail, Tzitzikas, Yannis, Hutchison, David, editor, Kanade, Takeo, editor, Kittler, Josef, editor, Kleinberg, Jon M., editor, Mattern, Friedemann, editor, Mitchell, John C., editor, Naor, Moni, editor, Nierstrasz, Oscar, editor, Pandu Rangan, C., editor, Steffen, Bernhard, editor, Sudan, Madhu, editor, Terzopoulos, Demetri, editor, Tygar, Doug, editor, Vardi, Moshe Y., editor, Weikum, Gerhard, editor, Salampasis, Michail, editor, and Larsen, Birger, editor

Published
2012
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100. Conclusions

Author

Sacco, Giovanni Maria, Tzitzikas, Yannis, Sacco, Giovanni Maria, editor, and Tzitzikas, Yannis, editor

Published
2009
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