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Your search keyword '"Leonid Libkin"' showing total 116 results
Start Over Author "Leonid Libkin" Publication Type Academic Journals
116 results on '"Leonid Libkin"'

1. Order-Invariant Types and Their Applications

Author

Pablo Barcelo and Leonid Libkin

Subjects
computer science - logic in computer science, Logic, BC1-199, Electronic computers. Computer science, QA75.5-76.95
Abstract

Our goal is to show that the standard model-theoretic concept of types can be applied in the study of order-invariant properties, i.e., properties definable in a logic in the presence of an auxiliary order relation, but not actually dependent on that order relation. This is somewhat surprising since order-invariant properties are more of a combinatorial rather than a logical object. We provide two applications of this notion. One is a proof, from the basic principles, of a theorem by Courcelle stating that over trees, order-invariant MSO properties are expressible in MSO with counting quantifiers. The other is an analog of the Feferman-Vaught theorem for order-invariant properties.

Published
2016
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3. Graph Logics with Rational Relations

Author

Pablo Barcelo, Diego Figueira, and Leonid Libkin

Subjects
computer science - formal languages and automata theory, Logic, BC1-199, Electronic computers. Computer science, QA75.5-76.95
Abstract

We investigate some basic questions about the interaction of regular and rational relations on words. The primary motivation comes from the study of logics for querying graph topology, which have recently found numerous applications. Such logics use conditions on paths expressed by regular languages and relations, but they often need to be extended by rational relations such as subword or subsequence. Evaluating formulae in such extended graph logics boils down to checking nonemptiness of the intersection of rational relations with regular or recognizable relations (or, more generally, to the generalized intersection problem, asking whether some projections of a regular relation have a nonempty intersection with a given rational relation). We prove that for several basic and commonly used rational relations, the intersection problem with regular relations is either undecidable (e.g., for subword or suffix, and some generalizations), or decidable with non-primitive-recursive complexity (e.g., for subsequence and its generalizations). These results are used to rule out many classes of graph logics that freely combine regular and rational relations, as well as to provide the simplest problem related to verifying lossy channel systems that has non-primitive-recursive complexity. We then prove a dichotomy result for logics combining regular conditions on individual paths and rational relations on paths, by showing that the syntactic form of formulae classifies them into either efficiently checkable or undecidable cases. We also give examples of rational relations for which such logics are decidable even without syntactic restrictions.

Published
2013
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4. First-Order and Temporal Logics for Nested Words

Author

Rajeev Alur, Marcelo Arenas, Pablo Barcelo, Kousha Etessami, Neil Immerman, and Leonid Libkin

Subjects
computer science - logic in computer science, f.1.1, f.3.1, f.4.1, Logic, BC1-199, Electronic computers. Computer science, QA75.5-76.95
Abstract

Nested words are a structured model of execution paths in procedural programs, reflecting their call and return nesting structure. Finite nested words also capture the structure of parse trees and other tree-structured data, such as XML. We provide new temporal logics for finite and infinite nested words, which are natural extensions of LTL, and prove that these logics are first-order expressively-complete. One of them is based on adding a "within" modality, evaluating a formula on a subword, to a logic CaRet previously studied in the context of verifying properties of recursive state machines (RSMs). The other logic, NWTL, is based on the notion of a summary path that uses both the linear and nesting structures. For NWTL we show that satisfiability is EXPTIME-complete, and that model-checking can be done in time polynomial in the size of the RSM model and exponential in the size of the NWTL formula (and is also EXPTIME-complete). Finally, we prove that first-order logic over nested words has the three-variable property, and we present a temporal logic for nested words which is complete for the two-variable fragment of first-order.

Published
2008
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5. Logics for Unranked Trees: An Overview

Author

Leonid Libkin

Subjects
computer science - logic in computer science, computer science - databases, h.2.3, h.2.1, i.7, f.2.3, f.4.1, f.4.3, Logic, BC1-199, Electronic computers. Computer science, QA75.5-76.95
Abstract

Labeled unranked trees are used as a model of XML documents, and logical languages for them have been studied actively over the past several years. Such logics have different purposes: some are better suited for extracting data, some for expressing navigational properties, and some make it easy to relate complex properties of trees to the existence of tree automata for those properties. Furthermore, logics differ significantly in their model-checking properties, their automata models, and their behavior on ordered and unordered trees. In this paper we present a survey of logics for unranked trees.

Published
2006
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7. PG-Schema: Schemas for Property Graphs.

Author

Renzo Angles, Angela Bonifati, Stefania Dumbrava, George Fletcher 0001, Alastair Green, Jan Hidders, Bei Li, Leonid Libkin, Victor Marsault, Wim Martens, Filip Murlak, Stefan Plantikow, Ognjen Savkovic, Michael Schmidt, Juan Sequeda, Slawek Staworko, Dominik Tomaszuk, Hannes Voigt, Domagoj Vrgoc, Mingxi Wu, and Dusan Zivkovic

Published
2023
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10. The Linked Data Benchmark Council (LDBC): Driving competition and collaboration in the graph data management space.

Author

Gábor Szárnyas, Brad Bebee, Altan Birler, Alin Deutsch, George Fletcher 0001, Henry A. Gabb, Denise Gosnell, Alastair Green, Zhihui Guo, Keith W. Hare, Jan Hidders, Alexandru Iosup, Atanas Kiryakov, Tomas Kovatchev, Xinsheng Li, Leonid Libkin, Heng Lin, Xiaojian Luo, Arnau Prat-Pérez, David Püroja, Shipeng Qi, Oskar van Rest, Benjamin A. Steer, Dávid Szakállas, Bing Tong, Jack Waudby, Mingxi Wu, Bin Yang 0002, Wenyuan Yu, Chen Zhang, Jason Zhang, Yan Zhou, and Peter A. Boncz

Published
2023
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14. PG-Schema: Schemas for Property Graphs.

Author

Renzo Angles, Angela Bonifati, Stefania Dumbrava, George Fletcher 0001, Alastair Green, Jan Hidders, Bei Li, Leonid Libkin, Victor Marsault, Wim Martens, Filip Murlak, Stefan Plantikow, Ognjen Savkovic, Michael Schmidt, Juan Sequeda, Slawek Staworko, Dominik Tomaszuk, Hannes Voigt, Domagoj Vrgoc, Mingxi Wu, and Dusan Zivkovic

Published
2022
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18. Graph Pattern Matching in GQL and SQL/PGQ.

Author

Alin Deutsch, Nadime Francis, Alastair Green, Keith Hare, Bei Li, Leonid Libkin, Tobias Lindaaker, Victor Marsault, Wim Martens, Jan Michels, Filip Murlak, Stefan Plantikow, Petra Selmer, Hannes Voigt, Oskar van Rest, Domagoj Vrgoc, Mingxi Wu, and Fred Zemke

Published
2021

27. Research Directions for Principles of Data Management (Abridged).

Author

Serge Abiteboul, Marcelo Arenas, Pablo Barceló, Meghyn Bienvenu, Diego Calvanese, Claire David, Richard Hull 0001, Eyke Hüllermeier, Benny Kimelfeld, Leonid Libkin, Wim Martens, Tova Milo, Filip Murlak, Frank Neven, Magdalena Ortiz 0001, Thomas Schwentick, Julia Stoyanovich, Jianwen Su, Dan Suciu, Victor Vianu, and Ke Yi 0001

Published
2016
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30. Formal Semantics of the Language Cypher.

Author

Nadime Francis, Alastair Green, Paolo Guagliardo, Leonid Libkin, Tobias Lindaaker, Victor Marsault, Stefan Plantikow, Mats Rydberg, Martin Schuster, Petra Selmer, and Andrés Taylor

Published
2018

31. Data Context Informed Data Wrangling.

Author

Martin Koehler, Alex Bogatu, Cristina Civili, Nikolaos Konstantinou 0001, Edward Abel, Alvaro A. A. Fernandes, John A. Keane, Leonid Libkin, and Norman W. Paton

Published
2018

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