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109 results on '"Patroumpas, Kostas"'

1. Accelerating Spatio-Textual Queries with Learned Indices

Author

Chatzigeorgakidis, Georgios, Patroumpas, Kostas, Skoutas, Dimitrios, and Athanasiou, Spiros

Subjects
Computer Science - Data Structures and Algorithms
Abstract

Efficiently computing spatio-textual queries has become increasingly important in various applications that need to quickly retrieve geolocated entities associated with textual information, such as in location-based services and social networks. To accelerate such queries, several works have proposed combining spatial and textual indices into hybrid index structures. Recently, the novel idea of replacing traditional indices with ML models has attracted a lot of attention. This includes works on learned spatial indices, where the main challenge is to address the lack of a total ordering among objects in a multidimensional space. In this work, we investigate how to extend this novel type of index design to the case of spatio-textual data. We study different design choices, based on either loose or tight coupling between the spatial and textual part, as well as a hybrid index that combines a traditional and a learned component. We also perform an experimental evaluation using several real-world datasets to assess the potential benefits of using a learned index for evaluating spatio-textual queries.

Published
2023

3. Local Similarity Search on Geolocated Time Series Using Hybrid Indexing

Author

Chatzigeorgakidis, Georgios, Skoutas, Dimitrios, Patroumpas, Kostas, Palpanas, Themis, Athanasiou, Spiros, and Skiadopoulos, Spiros

Subjects
Computer Science - Databases, 68P05, E.1
Abstract

Geolocated time series, i.e., time series associated with certain locations, abound in many modern applications. In this paper, we consider hybrid queries for retrieving geolocated time series based on filters that combine spatial distance and time series similarity. For the latter, unlike existing work, we allow filtering based on local similarity, which is computed based on subsequences rather than the entire length of each series, thus allowing the discovery of more fine-grained trends and patterns. To efficiently support such queries, we first leverage the state-of-the-art BTSR-tree index, which utilizes bounds over both the locations and the shapes of time series to prune the search space. Moreover, we propose optimizations that check at specific timestamps to identify candidate time series that may exceed the required local similarity threshold. To further increase pruning power, we introduce the SBTSR-tree index, an extension to BTSR-tree, which additionally segments the time series temporally, allowing the construction of tighter bounds. Our experimental results on several real-world datasets demonstrate that SBTSR-tree can provide answers much faster for all examined query types. This paper has been published in the 27th International Conference on Advances in Geographic Information Systems (ACM SIGSPATIAL 2019).

Published
2021

4. Local Pair and Bundle Discovery over Co-Evolving Time Series

Author

Chatzigeorgakidis, Georgios, Skoutas, Dimitrios, Patroumpas, Kostas, Palpanas, Themis, Athanasiou, Spiros, and Skiadopoulos, Spiros

Subjects
Computer Science - Data Structures and Algorithms, 68P05, E.1
Abstract

Time series exploration and mining has many applications across several industrial and scientific domains. In this paper, we consider the problem of detecting locally similar pairs and groups, called bundles, over co-evolving time series. These are pairs or groups of subsequences whose values do not differ by more than {\epsilon} for at least delta consecutive timestamps, thus indicating common local patterns and trends. We first present a baseline algorithm that performs a sweep line scan across all timestamps to identify matches. Then, we propose a filter-verification technique that only examines candidate matches at judiciously chosen checkpoints across time. Specifically, we introduce two block scanning algorithms for discovering local pairs and bundles respectively, which leverage the potential of checkpoints to aggressively prune the search space. We experimentally evaluate our methods against real-world and synthetic datasets, demonstrating a speed-up in execution time by an order of magnitude over the baseline. This paper has been published in the 16th International Symposium on Spatial and Temporal Databases (SSTD19)., Comment: 16 pages, 16 figures

Published
2021

5. Twin Subsequence Search in Time Series

Author

Chatzigeorgakidis, Georgios, Skoutas, Dimitrios, Patroumpas, Kostas, Palpanas, Themis, Athanasiou, Spiros, and Skiadopoulos, Spiros

Subjects
Computer Science - Data Structures and Algorithms, 68P05, E.1
Abstract

We address the problem of subsequence search in time series using Chebyshev distance, to which we refer as twin subsequence search. We first show how existing time series indices can be extended to perform twin subsequence search. Then, we introduce TS-Index, a novel index tailored to this problem. Our experimental evaluation compares these approaches against real time series datasets, and demonstrates that TS-Index can retrieve twin subsequences much faster under various query conditions. This paper has been published in the 24th International Conference on Extending Database Technology (EDBT 2021)., Comment: 6 pages, 8 figures

Published
2021

6. Topio: An Open-Source Web Platform for Trading Geospatial Data

Author

Ionescu, Andra, Patroumpas, Kostas, Psarakis, Kyriakos, Chatzigeorgakidis, Georgios, Collarana, Diego, Barenscher, Kai, Skoutas, Dimitrios, Katsifodimos, Asterios, Athanasiou, Spiros, Goos, Gerhard, Founding Editor, Hartmanis, Juris, Founding Editor, Bertino, Elisa, Editorial Board Member, Gao, Wen, Editorial Board Member, Steffen, Bernhard, Editorial Board Member, Yung, Moti, Editorial Board Member, Garrigós, Irene, editor, Murillo Rodríguez, Juan Manuel, editor, and Wimmer, Manuel, editor

Published
2023
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7. Optimizing Vessel Trajectory Compression

Author

Fikioris, Giannis, Patroumpas, Kostas, and Artikis, Alexander

Subjects
Computer Science - Computer Vision and Pattern Recognition, Computer Science - Artificial Intelligence, Electrical Engineering and Systems Science - Image and Video Processing
Abstract

In previous work we introduced a trajectory detection module that can provide summarized representations of vessel trajectories by consuming AIS positional messages online. This methodology can provide reliable trajectory synopses with little deviations from the original course by discarding at least 70% of the raw data as redundant. However, such trajectory compression is very sensitive to parametrization. In this paper, our goal is to fine-tune the selection of these parameter values. We take into account the type of each vessel in order to provide a suitable configuration that can yield improved trajectory synopses, both in terms of approximation error and compression ratio. Furthermore, we employ a genetic algorithm converging to a suitable configuration per vessel type. Our tests against a publicly available AIS dataset have shown that compression efficiency is comparable or even better than the one with default parametrization without resorting to a laborious data inspection.

Published
2020

9. Trajectory Detection and Summarization over Surveillance Data Streams

Author

Patroumpas, Kostas, Chondrodima, Eva, Pelekis, Nikos, Theodoridis, Yannis, Vouros, George A., editor, Andrienko, Gennady, editor, Doulkeridis, Christos, editor, Pelekis, Nikolaos, editor, Artikis, Alexander, editor, Jousselme, Anne-Laure, editor, Ray, Cyril, editor, Cordero, Jose Manuel, editor, and Scarlatti, David, editor

Published
2020
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10. Online Event Recognition from Moving Vessel Trajectories

Author

Patroumpas, Kostas, Alevizos, Elias, Artikis, Alexander, Vodas, Marios, Pelekis, Nikos, and Theodoridis, Yannis

Subjects
Computer Science - Computer Vision and Pattern Recognition, Computer Science - Artificial Intelligence
Abstract

We present a system for online monitoring of maritime activity over streaming positions from numerous vessels sailing at sea. It employs an online tracking module for detecting important changes in the evolving trajectory of each vessel across time, and thus can incrementally retain concise, yet reliable summaries of its recent movement. In addition, thanks to its complex event recognition module, this system can also offer instant notification to marine authorities regarding emergency situations, such as risk of collisions, suspicious moves in protected zones, or package picking at open sea. Not only did our extensive tests validate the performance, efficiency, and robustness of the system against scalable volumes of real-world and synthetically enlarged datasets, but its deployment against online feeds from vessels has also confirmed its capabilities for effective, real-time maritime surveillance.

Published
2016
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12. Spatial Selectivity Estimation for Web Searching

Author

Patroumpas, Kostas, 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, Gensel, Jérôme, editor, and Tomko, Martin, editor

Published
2015
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13. Topio Marketplace: Search and Discovery of Geospatial Data

Author

Ionescu, A., Alexandridou, Alexandra, Ikonomou, Leonidas, Psarakis, K., Patroumpas, Kostas, Chatzigeorgakidis, Georgios, Skoutas, Dimitrios, Athanasiou, Spiros, Hai, R., and Katsifodimos, A

Abstract

The increasing need for data trading has created a high demand for data marketplaces. These marketplaces require a set of value-added services, such as advanced search and discovery, that have been proposed in the database research community for years, but are yet to be put to practice. In this paper we propose to demonstrate the Topio Marketplace, an open-source data market platform that facilitates the search, exploration, discovery and augmentation of data assets. To support filtering, searching and discovery of data assets, we developed methods to extract and visualise a variety of metadata, as well as methods to discover related assets and mechanism to augment them. This paper aims at presenting these methods with a real deployment of the Topio marketplace, comprising hundreds of open and proprietary datasets.

Published
2023

15. Multi-scale Windowing over Trajectory Streams

Author

Patroumpas, Kostas, 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, Castano, Silvana, editor, Vassiliadis, Panos, editor, Lakshmanan, Laks V., editor, and Lee, Mong Li, editor

Published
2012
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16. Probabilistic Range Monitoring of Streaming Uncertain Positions in GeoSocial Networks

Author

Patroumpas, Kostas, Papamichalis, Marios, Sellis, Timos, 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, Ailamaki, Anastasia, editor, and Bowers, Shawn, editor

Published
2012
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17. Multiplexing Trajectories of Moving Objects

Author

Patroumpas, Kostas, Toumbas, Kyriakos, Sellis, Timos, 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, Ailamaki, Anastasia, editor, and Bowers, Shawn, editor

Published
2012
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18. Event Processing and Real-Time Monitoring over Streaming Traffic Data

Author

Patroumpas, Kostas, Sellis, Timos, 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, Di Martino, Sergio, editor, Peron, Adriano, editor, and Tezuka, Taro, editor

Published
2012
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19. Subsuming Multiple Sliding Windows for Shared Stream Computation

Author

Patroumpas, Kostas, Sellis, Timos, 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, Nierstrasz, Oscar, Series editor, Pandu Rangan, C., Series editor, Steffen, Bernhard, Series editor, Sudan, Madhu, Series editor, Terzopoulos, Demetri, Series editor, Tygar, Doug, Series editor, Vardi, Moshe Y., Series editor, Weikum, Gerhard, Series editor, Eder, Johann, editor, Bielikova, Maria, editor, and Tjoa, A Min, editor

Published
2011
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21. Window Update Patterns in Stream Operators

Author

Patroumpas, Kostas, Sellis, Timos, 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, Nierstrasz, Oscar, Series editor, Pandu Rangan, C., Series editor, Steffen, Bernhard, Series editor, Sudan, Madhu, Series editor, Terzopoulos, Demetri, Series editor, Tygar, Doug, Series editor, Vardi, Moshe Y., Series editor, Weikum, Gerhard, Series editor, Grundspenkis, Janis, editor, Morzy, Tadeusz, editor, and Vossen, Gottfried, editor

Published
2009
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22. Monitoring Orientation of Moving Objects around Focal Points

Author

Patroumpas, Kostas, Sellis, Timos, 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, Nierstrasz, Oscar, Series editor, Pandu Rangan, C., Series editor, Steffen, Bernhard, Series editor, Sudan, Madhu, Series editor, Terzopoulos, Demetri, Series editor, Tygar, Doug, Series editor, Vardi, Moshe Y., Series editor, Weikum, Gerhard, Series editor, Mamoulis, Nikos, editor, Seidl, Thomas, editor, Pedersen, Torben Bach, editor, Torp, Kristian, editor, and Assent, Ira, editor

Published
2009
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24. Prioritized Evaluation of Continuous Moving Queries over Streaming Locations

Author

Patroumpas, Kostas, Sellis, Timos, 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, Ludäscher, Bertram, editor, and Mamoulis, Nikos, editor

Published
2008
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25. Online Amnesic Summarization of Streaming Locations

Author

Potamias, Michalis, Patroumpas, Kostas, Sellis, Timos, 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, Papadias, Dimitris, editor, Zhang, Donghui, editor, and Kollios, George, editor

Published
2007
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26. Window Specification over Data Streams

Author

Patroumpas, Kostas, Sellis, Timos, 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, Dough, editor, Vardi, Moshe Y., editor, Weikum, Gerhard, editor, Grust, Torsten, editor, Höpfner, Hagen, editor, Illarramendi, Arantza, editor, Jablonski, Stefan, editor, Mesiti, Marco, editor, Müller, Sascha, editor, Patranjan, Paula-Lavinia, editor, Sattler, Kai-Uwe, editor, Spiliopoulou, Myra, editor, and Wijsen, Jef, editor

Published
2006
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31. Multi-Attribute Similarity Search for Interactive Data Exploration

Author

Patroumpas, Kostas, Zeakis, Alexandros, Skoutas, Dimitrios, and Santoro, Roberto

Abstract

We have developed SimSearch, a tool that simplifies data exploration by enabling top-k similarity search over large collections of entities involving multiple heterogeneous attributes from different sources. We present the supported modes for data access, and the query mechanism orchestrating multi-attribute similarity search over diverse types of attributes, including textual, numerical and spatial. Users can specify their query parameters and preferences through a web interface, and visually inspect and compare the results through appropriate visualizations for the different types of attributes involved. We demonstrate SimSearch using a real-world, commercial dataset, highlighting its capabilities for interactive, user-friendly, and intuitive data exploration.

Published
2021
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32. Efficient Range and kNN Twin Subsequence Search in Time Series

Author

Chatzigeorgakidis, Georgios, Skoutas, Dimitrios, Patroumpas, Kostas, Palpanas, Themis, Athanasiou, Spiros, and Skiadopoulos, Spiros

Abstract

Analyzing time series data is crucial for many applications. In particular, subsequence search refers to finding subsequences within an input time series $T$T that are similar to a query sequence $Q$Q. Existing subsequence search approaches typically employ Euclidean distance or Dynamic Time Warping as similarity measures and address range queries. In this paper, we focus on Chebyshev distance, which is the largest difference between each individual pair of points across the entire length of two compared subsequences. We call such similar pairs twins. We first show how existing time series indices can be extended to perform twin subsequence search. Then, we introduce TS-Index, a novel index tailored to the computation of twin subsequence search queries. Moreover, given that specifying a distance threshold is often not straightforward, we show how TS-Index can also be used to evaluate $k$kNN queries. Our extensive experimental evaluation compares these approaches using real time series datasets. The results demonstrate that TS-Index can retrieve twin subsequences faster than all other methods under various conditions.

Published
2023
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34. SLIPO

Author

Alexakis, Michalis, primary, Athanasiou, Spiros, additional, Kouvaras, Yannis, additional, Patroumpas, Kostas, additional, and Skoutas, Dimitrios, additional

Published
2020
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41. SPHINX

Author

Chatzopoulos, Serafeim, primary, Patroumpas, Kostas, additional, Zeakis, Alexandros, additional, Vergoulis, Thanasis, additional, and Skoutas, Dimitrios, additional

Published
2020
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48. ARGO

Author

Petrou, Petros, primary, Nikitopoulos, Panagiotis, additional, Tampakis, Panagiotis, additional, Glenis, Apostolos, additional, Koutroumanis, Nikolaos, additional, Santipantakis, Georgios M., additional, Patroumpas, Kostas, additional, Vlachou, Akrivi, additional, Georgiou, Harris, additional, Chondrodima, Eva, additional, Doulkeridis, Christos, additional, Pelekis, Nikos, additional, Andrienko, Gennady L., additional, Patterson, Fabian, additional, Fuchs, Georg, additional, Theodoridis, Yannis, additional, and Vouros, George A., additional

Published
2019
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