Valda Seminar: Michaël Thomazo

14 January 2022, 10:30-11:30 ENS, S16 Capturing Homomorphism-Closed Decidable Queries with Existential Rules Existential rules are a well studied ontology-mediated query language for which the chase represents a generic computational approach for query answering. It is straightforward that existential rule queries exhibiting chase termination are decidable and can only recognize…

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Valda Seminar: Davide Benedetto and Shrey Mishra

12 March 2021, 10:30-11:30 Online seminar: https://bbb.di.ens.fr/b/cam-pz6-kdj Traversal algorithms and heuristics for reasoning over logic based knowledge graphs (Davide Benedetto) Knowledge Graphs (KGs) provide a concise and intuitive abstraction for a variety of domains where edges capture the (potentially recursive) relationships between the entities. This is leading to the rise…

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Valda Seminar: Liat Peterfreund and Yann Ramusat

5 March 2021, 10:30-11:30 Online seminar: https://bbb.di.ens.fr/b/cam-pz6-kdj Grammars for Document Spanners (Liat Peterfreund) We propose a new grammar-based language for defining information-extractors from documents (text) that is built upon the well-studied framework of Document Spanners for extracting structured data from text. While previously studied formalisms for document spanners are mainly…

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Valda Seminar: Meghyn Bienvenu

Meghyn Bienvenu, CNRS, University of Bordeaux 18 December 2020, 10:30-11:30 Online seminar: https://bbb.di.ens.fr/b/cam-pz6-kdj Preferred repairs over inconsistent knowledge bases and connections to argumentation A fundamental notion when reasoning over inconsistent knowledge bases is that of a repair, defined as a maximal subset of the data that is consistent w.r.t. the…

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Valda Seminar : Val Tannen

Val Tannen, University of Pennsylvania 21 February 2020, 10:00-11:00 ENS, S16 Provenance Analysis for First-order Model Checking Is a given finite structure a model of a given first-order sentence? The provenance analysis of this question determines how its answer depends on the atomic facts that determine the structure. Provenance questions…

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Valda Seminar: Nofar Carmeli

Nofar Carmeli, Technion, Israel Institute of Technology 28 February 2020, 10:30-11:30 ENS, S16 The Complexity of Answering Unions of Conjunctive Queries We discuss the complexity of enumerating (listing) the answers to a query over a relational database. In particular, we consider three variants: arbitrary order, uniformly random order, and random…

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Valda Seminar: Evgenia Ternovska

Evgenia (Eugenia) Ternovska Associate Professor | School of Computing Science Simon Fraser University 8888 University Dr., Burnaby, B.C. V5A 1S6 13 February 2020, 10:30-11:30 ENS, S16 Logic of Information Flows: Expressing Reachability and Cardinality Properties A challenge in descriptive complexity is to identify logics with low complexity that simultaneously express…

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Valda Seminar: Silviu Maniu

Silviu Maniu, Université Paris-Sud 7 February 2020, 10:30-11:30 ENS, S16 An Experimental Study of the Treewidth of Real-World Data Treewidth is a parameter that measures how tree-like a data instance is, and whether it can reasonably be decomposed into a data structure resembling a tree. Many computation tasks are known…

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Valda Seminar: Juan Sequeda

Juan Sequeda 29 November 2019, 10:30-11:30 ENS, S16 A Brief History of Knowledge Graph’s Main Ideas Knowledge Graphs can be considered to be fulfilling an early vision in Computer Science of creating intelligent systems that integrate knowledge and data at large scale. The term “Knowledge Graph” has rapidly gained popularity…

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Valda Seminar: Julien Grange

6 December 2019, 10:30-11:30 ENS, S16 Order-invariant first-order logic over hollow trees. Order-invariant first-order logic is the extension of first-order logic in which the usage of an additional ordering relation on the structure’s universe is allowed, provided that the evaluation of sentences is independent of the choice of a particular…

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