47 Search Results for "Rodrigues, Luís"

Volume

OASIcs, Volume 74

8th Symposium on Languages, Applications and Technologies (SLATE 2019)

SLATE 2019, June 27-28, 2019, Coimbra, Portugal

Editors: Ricardo Rodrigues, Jan Janoušek, Luís Ferreira, Luísa Coheur, Fernando Batista, and Hugo Gonçalo Oliveira

Volume

LIPIcs, Volume 125

22nd International Conference on Principles of Distributed Systems (OPODIS 2018)

OPODIS 2018, December 17-19, 2018, Hong Kong, China

Editors: Jiannong Cao, Faith Ellen, Luis Rodrigues, and Bernardo Ferreira

Document
DOI: 10.4230/LITES.8.2.2
Swarms of Mobile Robots: Towards Versatility with Safety

Authors: Pierre Courtieu, Lionel Rieg, Sébastien Tixeuil, and Xavier Urbain

Published in: LITES, Volume 8, Issue 2 (2022): Special Issue on Distributed Hybrid Systems. Leibniz Transactions on Embedded Systems, Volume 8, Issue 2

Abstract
We present Pactole, a formal framework to design and prove the correctness of protocols (or the impossibility of their existence) that target mobile robotic swarms. Unlike previous approaches, our methodology unifies in a single formalism the execution model, the problem specification, the protocol, and its proof of correctness. The Pactole framework makes use of the Coq proof assistant, and is specially targeted at protocol designers and problem specifiers, so that a common unambiguous language is used from the very early stages of protocol development. We stress the underlying framework design principles to enable high expressivity and modularity, and provide concrete examples about how the Pactole framework can be used to tackle actual problems, some previously addressed by the Distributed Computing community, but also new problems, while being certified correct.
Cite as

Pierre Courtieu, Lionel Rieg, Sébastien Tixeuil, and Xavier Urbain. Swarms of Mobile Robots: Towards Versatility with Safety. In LITES, Volume 8, Issue 2 (2022): Special Issue on Distributed Hybrid Systems. Leibniz Transactions on Embedded Systems, Volume 8, Issue 2, pp. 02:1-02:36, Schloss Dagstuhl - Leibniz-Zentrum für Informatik (2022)

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@Article{courtieu_et_al:LITES.8.2.2,
  author =	{Courtieu, Pierre and Rieg, Lionel and Tixeuil, S\'{e}bastien and Urbain, Xavier},
  title =	{{Swarms of Mobile Robots: Towards Versatility with Safety}},
  booktitle =	{LITES, Volume 8, Issue 2 (2022): Special Issue on Distributed Hybrid Systems},
  pages =	{02:1--02:36},
  journal =	{Leibniz Transactions on Embedded Systems},
  ISSN =	{2199-2002},
  year =	{2022},
  volume =	{8},
  number =	{2},
  editor =	{Courtieu, Pierre and Rieg, Lionel and Tixeuil, S\'{e}bastien and Urbain, Xavier},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LITES.8.2.2},
  doi =		{10.4230/LITES.8.2.2},
  annote =	{Keywords: distributed algorithm, mobile autonomous robots, formal proof}
}
Document
DOI: 10.4230/OASIcs.SLATE.2022.3
Question Answering For Toxicological Information Extraction

Authors: Bruno Carlos Luís Ferreira, Hugo Gonçalo Oliveira, Hugo Amaro, Ângela Laranjeiro, and Catarina Silva

Published in: OASIcs, Volume 104, 11th Symposium on Languages, Applications and Technologies (SLATE 2022)

Abstract
Working with large amounts of text data has become hectic and time-consuming. In order to reduce human effort, costs, and make the process more efficient, companies and organizations resort to intelligent algorithms to automate and assist the manual work. This problem is also present in the field of toxicological analysis of chemical substances, where information needs to be searched from multiple documents. That said, we propose an approach that relies on Question Answering for acquiring information from unstructured data, in our case, English PDF documents containing information about physicochemical and toxicological properties of chemical substances. Experimental results confirm that our approach achieves promising results which can be applicable in the business scenario, especially if further revised by humans.
Cite as

Bruno Carlos Luís Ferreira, Hugo Gonçalo Oliveira, Hugo Amaro, Ângela Laranjeiro, and Catarina Silva. Question Answering For Toxicological Information Extraction. In 11th Symposium on Languages, Applications and Technologies (SLATE 2022). Open Access Series in Informatics (OASIcs), Volume 104, pp. 3:1-3:10, Schloss Dagstuhl - Leibniz-Zentrum für Informatik (2022)

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@InProceedings{ferreira_et_al:OASIcs.SLATE.2022.3,
  author =	{Ferreira, Bruno Carlos Lu{\'\i}s and Gon\c{c}alo Oliveira, Hugo and Amaro, Hugo and Laranjeiro, \^{A}ngela and Silva, Catarina},
  title =	{{Question Answering For Toxicological Information Extraction}},
  booktitle =	{11th Symposium on Languages, Applications and Technologies (SLATE 2022)},
  pages =	{3:1--3:10},
  series =	{Open Access Series in Informatics (OASIcs)},
  ISBN =	{978-3-95977-245-7},
  ISSN =	{2190-6807},
  year =	{2022},
  volume =	{104},
  editor =	{Cordeiro, Jo\~{a}o and Pereira, Maria Jo\~{a}o and Rodrigues, Nuno F. and Pais, Sebasti\~{a}o},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/OASIcs.SLATE.2022.3},
  URN =		{urn:nbn:de:0030-drops-167493},
  doi =		{10.4230/OASIcs.SLATE.2022.3},
  annote =	{Keywords: Information Extraction, Question Answering, Transformers, Toxicological Analysis}
}
Document
DOI: 10.4230/OASIcs.SLATE.2022.9
Classification of Public Administration Complaints

Authors: Francisco Caldeira, Luís Nunes, and Ricardo Ribeiro

Published in: OASIcs, Volume 104, 11th Symposium on Languages, Applications and Technologies (SLATE 2022)

Abstract
Complaint management is a problem faced by many organizations that is both vital to customer image and highly dependent on human resources. This work attempts to tackle a part of the problem, by classifying summaries of complaints using machine learning models in order to better redirect these to the appropriate responders. The main challenges of this task is that training datasets are often small and highly imbalanced. This can can have a big impact on the performance of classification models. The dataset analyzed in this work suffers from both of these problems, being relatively small and having labels in different proportions. In this work, two different techniques are analyzed: combining classes together to increase the number of elements of the new class; and, providing new artificial examples for some classes via translation into other languages. The classification models explored were the following: k-NN, SVM, Naïve Bayes, boosting, and Deep Learning approaches, including transformers. The paper concludes that although, as expected, the classes with little representation are hard to classify, the techniques explored helped to boost the performance, especially in the classes with a low number of elements. SVM and BERT-based models outperformed their peers.
Cite as

Francisco Caldeira, Luís Nunes, and Ricardo Ribeiro. Classification of Public Administration Complaints. In 11th Symposium on Languages, Applications and Technologies (SLATE 2022). Open Access Series in Informatics (OASIcs), Volume 104, pp. 9:1-9:12, Schloss Dagstuhl - Leibniz-Zentrum für Informatik (2022)

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@InProceedings{caldeira_et_al:OASIcs.SLATE.2022.9,
  author =	{Caldeira, Francisco and Nunes, Lu{\'\i}s and Ribeiro, Ricardo},
  title =	{{Classification of Public Administration Complaints}},
  booktitle =	{11th Symposium on Languages, Applications and Technologies (SLATE 2022)},
  pages =	{9:1--9:12},
  series =	{Open Access Series in Informatics (OASIcs)},
  ISBN =	{978-3-95977-245-7},
  ISSN =	{2190-6807},
  year =	{2022},
  volume =	{104},
  editor =	{Cordeiro, Jo\~{a}o and Pereira, Maria Jo\~{a}o and Rodrigues, Nuno F. and Pais, Sebasti\~{a}o},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/OASIcs.SLATE.2022.9},
  URN =		{urn:nbn:de:0030-drops-167555},
  doi =		{10.4230/OASIcs.SLATE.2022.9},
  annote =	{Keywords: Text Classification, Natural Language Processing, Deep Learning, BERT}
}
Document
DOI: 10.4230/OASIcs.SLATE.2022.17
Reasoning with Portuguese Word Embeddings

Authors: Luís Filipe Cunha, J. João Almeida, and Alberto Simões

Published in: OASIcs, Volume 104, 11th Symposium on Languages, Applications and Technologies (SLATE 2022)

Abstract
Representing words with semantic distributions to create ML models is a widely used technique to perform Natural Language processing tasks. In this paper, we trained word embedding models with different types of Portuguese corpora, analyzing the influence of the models' parameterization, the corpora size, and domain. Then we validated each model with the classical evaluation methods available: four words analogies and measurement of the similarity of pairs of words. In addition to these methods, we proposed new alternative techniques to validate word embedding models, presenting new resources for this purpose. Finally, we discussed the obtained results and argued about some limitations of the word embedding models' evaluation methods.
Cite as

Luís Filipe Cunha, J. João Almeida, and Alberto Simões. Reasoning with Portuguese Word Embeddings. In 11th Symposium on Languages, Applications and Technologies (SLATE 2022). Open Access Series in Informatics (OASIcs), Volume 104, pp. 17:1-17:14, Schloss Dagstuhl - Leibniz-Zentrum für Informatik (2022)

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@InProceedings{cunha_et_al:OASIcs.SLATE.2022.17,
  author =	{Cunha, Lu{\'\i}s Filipe and Almeida, J. Jo\~{a}o and Sim\~{o}es, Alberto},
  title =	{{Reasoning with Portuguese Word Embeddings}},
  booktitle =	{11th Symposium on Languages, Applications and Technologies (SLATE 2022)},
  pages =	{17:1--17:14},
  series =	{Open Access Series in Informatics (OASIcs)},
  ISBN =	{978-3-95977-245-7},
  ISSN =	{2190-6807},
  year =	{2022},
  volume =	{104},
  editor =	{Cordeiro, Jo\~{a}o and Pereira, Maria Jo\~{a}o and Rodrigues, Nuno F. and Pais, Sebasti\~{a}o},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/OASIcs.SLATE.2022.17},
  URN =		{urn:nbn:de:0030-drops-167636},
  doi =		{10.4230/OASIcs.SLATE.2022.17},
  annote =	{Keywords: Word Embeddings, Word2Vec, Evaluation Methods}
}
Document
Complete Volume
DOI: 10.4230/OASIcs.SLATE.2019
OASIcs, Volume 74, SLATE'19, Complete Volume

Authors: Ricardo Rodrigues, Jan Janoušek, Luís Ferreira, Luísa Coheur, Fernando Batista, and Hugo Gonçalo Oliveira

Published in: OASIcs, Volume 74, 8th Symposium on Languages, Applications and Technologies (SLATE 2019)

Abstract
OASIcs, Volume 74, SLATE'19, Complete Volume
Cite as

Ricardo Rodrigues, Jan Janoušek, Luís Ferreira, Luísa Coheur, Fernando Batista, and Hugo Gonçalo Oliveira. OASIcs, Volume 74, SLATE'19, Complete Volume. In 8th Symposium on Languages, Applications and Technologies (SLATE 2019). Open Access Series in Informatics (OASIcs), Volume 74, Schloss Dagstuhl - Leibniz-Zentrum für Informatik (2019)

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@Proceedings{rodrigues_et_al:OASIcs.SLATE.2019,
  title =	{{OASIcs, Volume 74, SLATE'19, Complete Volume}},
  booktitle =	{8th Symposium on Languages, Applications and Technologies (SLATE 2019)},
  series =	{Open Access Series in Informatics (OASIcs)},
  ISBN =	{978-3-95977-114-6},
  ISSN =	{2190-6807},
  year =	{2019},
  volume =	{74},
  editor =	{Rodrigues, Ricardo and Janou\v{s}ek, Jan and Ferreira, Lu{\'\i}s and Coheur, Lu{\'\i}sa and Batista, Fernando and Gon\c{c}alo Oliveira, Hugo},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/OASIcs.SLATE.2019},
  URN =		{urn:nbn:de:0030-drops-109008},
  doi =		{10.4230/OASIcs.SLATE.2019},
  annote =	{Keywords: Computing methodologies, Natural language processing, Software and its engineering, Compilers; Information systems, World Wide Web}
}
Document
Front Matter
DOI: 10.4230/OASIcs.SLATE.2019.0
Front Matter, Table of Contents, Preface, Conference Organization

Authors: Ricardo Rodrigues, Jan Janoušek, Luís Ferreira, Luísa Coheur, Fernando Batista, and Hugo Gonçalo Oliveira

Published in: OASIcs, Volume 74, 8th Symposium on Languages, Applications and Technologies (SLATE 2019)

Abstract
Front Matter, Table of Contents, Preface, Conference Organization
Cite as

Ricardo Rodrigues, Jan Janoušek, Luís Ferreira, Luísa Coheur, Fernando Batista, and Hugo Gonçalo Oliveira. Front Matter, Table of Contents, Preface, Conference Organization. In 8th Symposium on Languages, Applications and Technologies (SLATE 2019). Open Access Series in Informatics (OASIcs), Volume 74, pp. 0:i-0:xviii, Schloss Dagstuhl - Leibniz-Zentrum für Informatik (2019)

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@InProceedings{rodrigues_et_al:OASIcs.SLATE.2019.0,
  author =	{Rodrigues, Ricardo and Janou\v{s}ek, Jan and Ferreira, Lu{\'\i}s and Coheur, Lu{\'\i}sa and Batista, Fernando and Gon\c{c}alo Oliveira, Hugo},
  title =	{{Front Matter, Table of Contents, Preface, Conference Organization}},
  booktitle =	{8th Symposium on Languages, Applications and Technologies (SLATE 2019)},
  pages =	{0:i--0:xviii},
  series =	{Open Access Series in Informatics (OASIcs)},
  ISBN =	{978-3-95977-114-6},
  ISSN =	{2190-6807},
  year =	{2019},
  volume =	{74},
  editor =	{Rodrigues, Ricardo and Janou\v{s}ek, Jan and Ferreira, Lu{\'\i}s and Coheur, Lu{\'\i}sa and Batista, Fernando and Gon\c{c}alo Oliveira, Hugo},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/OASIcs.SLATE.2019.0},
  URN =		{urn:nbn:de:0030-drops-108679},
  doi =		{10.4230/OASIcs.SLATE.2019.0},
  annote =	{Keywords: Front Matter, Table of Contents, Preface, Conference Organization}
}
Document
DOI: 10.4230/OASIcs.SLATE.2019.15
Digital Collection Creator, Visualizer and Explorer

Authors: Luís F. Martins, Cristiana Araújo, and Pedro Rangel Henriques

Published in: OASIcs, Volume 74, 8th Symposium on Languages, Applications and Technologies (SLATE 2019)

Abstract
In this paper we introduce and discuss a recent project, called CortaColaEspia, aimed at extending with some extra relevant features the 'Ontology-based Collection Processor' developed previously in the context of a Compilers course. The basic processor, based on the OntoDL tool, was able to read the ontological description of a small collection of objects (cards, pencils, toys, etc.) and produce automatically a web-based exhibition space to display the objects, providing a conceptual navigation through them. The extension under discussion is intended to create a new DSL to describe the details of the exhibition room organization (what concepts and relations to show; where and how to show them; etc.). A second objective consists of a new module to merge two collections, or to enrich a collection with extra information about the collected objects. The last requirement is the incorporation of a natural language processor to analyze the objects' captions or short inscriptions in order to extract information that can create knowledge about a specific domain, a society or an epoch.
Cite as

Luís F. Martins, Cristiana Araújo, and Pedro Rangel Henriques. Digital Collection Creator, Visualizer and Explorer. In 8th Symposium on Languages, Applications and Technologies (SLATE 2019). Open Access Series in Informatics (OASIcs), Volume 74, pp. 15:1-15:8, Schloss Dagstuhl - Leibniz-Zentrum für Informatik (2019)

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@InProceedings{martins_et_al:OASIcs.SLATE.2019.15,
  author =	{Martins, Lu{\'\i}s F. and Ara\'{u}jo, Cristiana and Henriques, Pedro Rangel},
  title =	{{Digital Collection Creator, Visualizer and Explorer}},
  booktitle =	{8th Symposium on Languages, Applications and Technologies (SLATE 2019)},
  pages =	{15:1--15:8},
  series =	{Open Access Series in Informatics (OASIcs)},
  ISBN =	{978-3-95977-114-6},
  ISSN =	{2190-6807},
  year =	{2019},
  volume =	{74},
  editor =	{Rodrigues, Ricardo and Janou\v{s}ek, Jan and Ferreira, Lu{\'\i}s and Coheur, Lu{\'\i}sa and Batista, Fernando and Gon\c{c}alo Oliveira, Hugo},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/OASIcs.SLATE.2019.15},
  URN =		{urn:nbn:de:0030-drops-108829},
  doi =		{10.4230/OASIcs.SLATE.2019.15},
  annote =	{Keywords: Digital Collections, Ontology, DSL, Program Generation}
}
Document
Complete Volume
DOI: 10.4230/LIPIcs.OPODIS.2018
LIPIcs, Volume 125, OPODIS'18, Complete Volume

Authors: Jiannong Cao, Faith Ellen, Luis Rodrigues, and Bernardo Ferreira

Published in: LIPIcs, Volume 125, 22nd International Conference on Principles of Distributed Systems (OPODIS 2018)

Abstract
LIPIcs, Volume 125, OPODIS'18, Complete Volume
Cite as

Jiannong Cao, Faith Ellen, Luis Rodrigues, and Bernardo Ferreira. LIPIcs, Volume 125, OPODIS'18, Complete Volume. In 22nd International Conference on Principles of Distributed Systems (OPODIS 2018). Leibniz International Proceedings in Informatics (LIPIcs), Volume 125, Schloss Dagstuhl - Leibniz-Zentrum für Informatik (2019)

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@Proceedings{cao_et_al:LIPIcs.OPODIS.2018,
  title =	{{LIPIcs, Volume 125, OPODIS'18, Complete Volume}},
  booktitle =	{22nd International Conference on Principles of Distributed Systems (OPODIS 2018)},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-098-9},
  ISSN =	{1868-8969},
  year =	{2019},
  volume =	{125},
  editor =	{Cao, Jiannong and Ellen, Faith and Rodrigues, Luis and Ferreira, Bernardo},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.OPODIS.2018},
  URN =		{urn:nbn:de:0030-drops-101742},
  doi =		{10.4230/LIPIcs.OPODIS.2018},
  annote =	{Keywords: Computer systems organization, Dependable and fault-tolerant systems and networks, Computing methodologies, Distributed algorithms, Networks, Mobile networks, Wireless access networks, Ad hoc networks, Software and its engineering, Distributed systems organizing principles,}
}
Document
Front Matter
DOI: 10.4230/LIPIcs.OPODIS.2018.0
Front Matter, Table of Contents, Preface, Conference Organization

Authors: Jiannong Cao, Faith Ellen, Luis Rodrigues, and Bernardo Ferreira

Published in: LIPIcs, Volume 125, 22nd International Conference on Principles of Distributed Systems (OPODIS 2018)

Abstract
Front Matter, Table of Contents, Preface, Conference Organization
Cite as

Jiannong Cao, Faith Ellen, Luis Rodrigues, and Bernardo Ferreira. Front Matter, Table of Contents, Preface, Conference Organization. In 22nd International Conference on Principles of Distributed Systems (OPODIS 2018). Leibniz International Proceedings in Informatics (LIPIcs), Volume 125, pp. 0:i-0:xx, Schloss Dagstuhl - Leibniz-Zentrum für Informatik (2019)

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@InProceedings{cao_et_al:LIPIcs.OPODIS.2018.0,
  author =	{Cao, Jiannong and Ellen, Faith and Rodrigues, Luis and Ferreira, Bernardo},
  title =	{{Front Matter, Table of Contents, Preface, Conference Organization}},
  booktitle =	{22nd International Conference on Principles of Distributed Systems (OPODIS 2018)},
  pages =	{0:i--0:xx},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-098-9},
  ISSN =	{1868-8969},
  year =	{2019},
  volume =	{125},
  editor =	{Cao, Jiannong and Ellen, Faith and Rodrigues, Luis and Ferreira, Bernardo},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.OPODIS.2018.0},
  URN =		{urn:nbn:de:0030-drops-100607},
  doi =		{10.4230/LIPIcs.OPODIS.2018.0},
  annote =	{Keywords: Front Matter, Table of Contents, Preface, Conference Organization}
}
Document
Keynote
DOI: 10.4230/LIPIcs.OPODIS.2018.1
Complexity of Multi-Valued Register Simulations: A Retrospective (Keynote)

Authors: Jennifer L. Welch

Published in: LIPIcs, Volume 125, 22nd International Conference on Principles of Distributed Systems (OPODIS 2018)

Abstract
I will provide a historical perspective on wait-free simulations of multi-bit shared registers using single-bit shared registers, starting with classical results from the last century and ending with an overview of the recent resurgence of interest in the topic. Particular emphasis will be placed on the space and step complexities of such simulations.
Cite as

Jennifer L. Welch. Complexity of Multi-Valued Register Simulations: A Retrospective (Keynote). In 22nd International Conference on Principles of Distributed Systems (OPODIS 2018). Leibniz International Proceedings in Informatics (LIPIcs), Volume 125, p. 1:1, Schloss Dagstuhl - Leibniz-Zentrum für Informatik (2019)

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@InProceedings{welch:LIPIcs.OPODIS.2018.1,
  author =	{Welch, Jennifer L.},
  title =	{{Complexity of Multi-Valued Register Simulations: A Retrospective}},
  booktitle =	{22nd International Conference on Principles of Distributed Systems (OPODIS 2018)},
  pages =	{1:1--1:1},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-098-9},
  ISSN =	{1868-8969},
  year =	{2019},
  volume =	{125},
  editor =	{Cao, Jiannong and Ellen, Faith and Rodrigues, Luis and Ferreira, Bernardo},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.OPODIS.2018.1},
  URN =		{urn:nbn:de:0030-drops-100611},
  doi =		{10.4230/LIPIcs.OPODIS.2018.1},
  annote =	{Keywords: Distributed Systems}
}
Document
Keynote
DOI: 10.4230/LIPIcs.OPODIS.2018.2
Distributed Systems and Databases of the Globe Unite! The Cloud, the Edge and Blockchains (Keynote)

Authors: Amr El Abbadi

Published in: LIPIcs, Volume 125, 22nd International Conference on Principles of Distributed Systems (OPODIS 2018)

Abstract
Significant paradigm shifts are occurring in Access patterns are widely dispersed and large scale analysis requires real-time responses. Many of the fundamental challenges have been studied and explored by both the distributed systems and the database communities for decades. However, the current changing and scalable setting often requires a rethinking of basic assumptions and premises. The rise of the cloud computing paradigm with its global reach has resulted in novel approaches to integrate traditional concepts in novel guises to solve fault-tolerance and scalability challenges. This is especially the case when users require real-time global access. Exploiting edge cloud resources becomes critical for improved performance, which requires a reevaluation of many paradigms, even for a traditional problem like caching. The need for transparency and accessibility has led to innovative ways for managing large scale replicated logs and ledgers, giving rise to blockchains and their many applications. In this talk we will be explore some of these new trends while emphasizing the novel challenges they raise from both distributed systems as well as database points of view. We will propose a unifying framework for traditional consensus and commitment protocols, and discuss novel protocols that exploit edge computing resources to enhance performance. We will highlight the advantages and discuss the limitations of blockchains. Our overall goal is to explore approaches that unite and exploit many of the significant efforts made in distributed systems and databases to address the novel and pressing needs of today's global computing infrastructure.
Cite as

Amr El Abbadi. Distributed Systems and Databases of the Globe Unite! The Cloud, the Edge and Blockchains (Keynote). In 22nd International Conference on Principles of Distributed Systems (OPODIS 2018). Leibniz International Proceedings in Informatics (LIPIcs), Volume 125, p. 2:1, Schloss Dagstuhl - Leibniz-Zentrum für Informatik (2019)

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@InProceedings{abbadi:LIPIcs.OPODIS.2018.2,
  author =	{Abbadi, Amr El},
  title =	{{Distributed Systems and Databases of the Globe Unite! The Cloud, the Edge and Blockchains}},
  booktitle =	{22nd International Conference on Principles of Distributed Systems (OPODIS 2018)},
  pages =	{2:1--2:1},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-098-9},
  ISSN =	{1868-8969},
  year =	{2019},
  volume =	{125},
  editor =	{Cao, Jiannong and Ellen, Faith and Rodrigues, Luis and Ferreira, Bernardo},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.OPODIS.2018.2},
  URN =		{urn:nbn:de:0030-drops-100625},
  doi =		{10.4230/LIPIcs.OPODIS.2018.2},
  annote =	{Keywords: Consensus, Commitment, Cloud, Edge Computing, Blockchain}
}
Document
Keynote
DOI: 10.4230/LIPIcs.OPODIS.2018.3
How to Make Decisions (Optimally) (Keynote)

Authors: Siddhartha Sen

Published in: LIPIcs, Volume 125, 22nd International Conference on Principles of Distributed Systems (OPODIS 2018)

Abstract
Distributed systems are constantly faced with difficult decisions to make, such as in scheduling, caching, and traffic routing, to name a few. In most of these scenarios, the optimal decision is unknown and depends heavily on context. How can a system designer know if they have deployed the best decision-making policy, or if a different policy would perform better? As a community, we have developed a few methodologies for answering this question, some of them offline (e.g., simulation, trace-driven modeling) and some of them online (e.g., A/B testing). Neither approach is satisfactory: the offline methods suffer from bias and rely heavily on domain knowledge; the online methods are costly and difficult to deploy. What system designers ideally seek is the ability to ask "what if" questions about a policy without ever deploying it, which is called counterfactual evaluation. In this talk, I will show how reinforcement learning and causal inference can be synthesized to counterfactually evaluate a distributed system. We will apply this methodology to infrastructure systems in Azure, and face fundamental challenges and opportunities along the way. This talk will serve as an introduction to reinforcement learning and the counterfactual way of thinking, which I hope will interest and inspire the OPODIS community. I will start by introducing reinforcement learning (RL) as the right framework for modeling decisions in a distributed system. In RL, an agent learns by interacting with its environment: i.e., making decisions and receiving feedback for them. This is a stark contrast to traditional (supervised) learning, where the correct answer, or "label", is known. Since an RL agent does not know the correct answer, it must constantly explore its world by randomizing some of its decisions. Now it turns out that this randomization, if used correctly, can give us a special superpower: the ability to evaluate policies that have never been deployed. As magical as this may sound, we can use statistics to show that this evaluation is indeed correct. Unfortunately, applying this methodology to distributed systems is far from straightforward. Systems are complex, stateful amalgamations of components that navigate large decision spaces. We will need to wear both an RL hat and a systems hat to address these challenges. On the other hand, systems also present exciting opportunities. Many systems already use randomization in their decisions, e.g., to distribute data or work over replicas, or to manage resource contention. Sometimes, a conservative decision can implicitly yield feedback for other decisions: for example, when waiting for a timeout to expire, we automatically get feedback for what would have happened if we waited for any shorter amount of time. I will show how we can harvest this randomness and implicit feedback to achieve more effective counterfactual evaluation. We will apply all of the above ideas to two production infrastructure systems in Azure: a machine health monitor that decides when to reboot unresponsive machines, and a geo-distributed edge proxy that chooses the TCP configuration of each proxy machine. In both cases, we are able to counterfactually evaluate arbitrary policies with estimates that match the ground truth. Production environments raise interesting constraints and challenges, some of which are preventing us from scaling up our methodology. I will describe a possible path forward, and invite others in the community to contemplate these problems as well.
Cite as

Siddhartha Sen. How to Make Decisions (Optimally) (Keynote). In 22nd International Conference on Principles of Distributed Systems (OPODIS 2018). Leibniz International Proceedings in Informatics (LIPIcs), Volume 125, p. 3:1, Schloss Dagstuhl - Leibniz-Zentrum für Informatik (2019)

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@InProceedings{sen:LIPIcs.OPODIS.2018.3,
  author =	{Sen, Siddhartha},
  title =	{{How to Make Decisions (Optimally)}},
  booktitle =	{22nd International Conference on Principles of Distributed Systems (OPODIS 2018)},
  pages =	{3:1--3:1},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-098-9},
  ISSN =	{1868-8969},
  year =	{2019},
  volume =	{125},
  editor =	{Cao, Jiannong and Ellen, Faith and Rodrigues, Luis and Ferreira, Bernardo},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.OPODIS.2018.3},
  URN =		{urn:nbn:de:0030-drops-100638},
  doi =		{10.4230/LIPIcs.OPODIS.2018.3},
  annote =	{Keywords: reinforcement learning, distributed systems, counterfactual evaluation}
}
Document
DOI: 10.4230/LIPIcs.OPODIS.2018.4
Sparse Matrix Multiplication and Triangle Listing in the Congested Clique Model

Authors: Keren Censor-Hillel, Dean Leitersdorf, and Elia Turner

Published in: LIPIcs, Volume 125, 22nd International Conference on Principles of Distributed Systems (OPODIS 2018)

Abstract
We show how to multiply two n x n matrices S and T over semirings in the Congested Clique model, where n nodes communicate in a fully connected synchronous network using O(log{n})-bit messages, within O(nz(S)^{1/3} nz(T)^{1/3}/n + 1) rounds of communication, where nz(S) and nz(T) denote the number of non-zero elements in S and T, respectively. By leveraging the sparsity of the input matrices, our algorithm greatly reduces communication costs compared with general multiplication algorithms [Censor-Hillel et al., PODC 2015], and thus improves upon the state-of-the-art for matrices with o(n^2) non-zero elements. Moreover, our algorithm exhibits the additional strength of surpassing previous solutions also in the case where only one of the two matrices is such. Particularly, this allows to efficiently raise a sparse matrix to a power greater than 2. As applications, we show how to speed up the computation on non-dense graphs of 4-cycle counting and all-pairs-shortest-paths. Our algorithmic contribution is a new deterministic method of restructuring the input matrices in a sparsity-aware manner, which assigns each node with element-wise multiplication tasks that are not necessarily consecutive but guarantee a balanced element distribution, providing for communication-efficient multiplication. Moreover, this new deterministic method for restructuring matrices may be used to restructure the adjacency matrix of input graphs, enabling faster deterministic solutions for graph related problems. As an example, we present a new sparsity aware, deterministic algorithm which solves the triangle listing problem in O(m/n^{5/3} + 1) rounds, a complexity that was previously obtained by a randomized algorithm [Pandurangan et al., SPAA 2018], and that matches the known lower bound of Omega~(n^{1/3}) when m=n^2 of [Izumi and Le Gall, PODC 2017, Pandurangan et al., SPAA 2018]. Naturally, our triangle listing algorithm also implies triangle counting within the same complexity of O(m/n^{5/3} + 1) rounds, which is (possibly more than) a cubic improvement over the previously known deterministic O(m^2/n^3)-round algorithm [Dolev et al., DISC 2012].
Cite as

Keren Censor-Hillel, Dean Leitersdorf, and Elia Turner. Sparse Matrix Multiplication and Triangle Listing in the Congested Clique Model. In 22nd International Conference on Principles of Distributed Systems (OPODIS 2018). Leibniz International Proceedings in Informatics (LIPIcs), Volume 125, pp. 4:1-4:17, Schloss Dagstuhl - Leibniz-Zentrum für Informatik (2019)

Copy BibTex To Clipboard

@InProceedings{censorhillel_et_al:LIPIcs.OPODIS.2018.4,
  author =	{Censor-Hillel, Keren and Leitersdorf, Dean and Turner, Elia},
  title =	{{Sparse Matrix Multiplication and Triangle Listing in the Congested Clique Model}},
  booktitle =	{22nd International Conference on Principles of Distributed Systems (OPODIS 2018)},
  pages =	{4:1--4:17},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-098-9},
  ISSN =	{1868-8969},
  year =	{2019},
  volume =	{125},
  editor =	{Cao, Jiannong and Ellen, Faith and Rodrigues, Luis and Ferreira, Bernardo},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.OPODIS.2018.4},
  URN =		{urn:nbn:de:0030-drops-100645},
  doi =		{10.4230/LIPIcs.OPODIS.2018.4},
  annote =	{Keywords: congested clique, matrix multiplication, triangle listing}
}
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