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613 results on '"Libkin, Leonid"'

601. Constraint databases: A survey

Author

Revesz, Peter Z., Goos, Gerhard, editor, Hartmanis, Juris, editor, van Leeuwen, Jan, editor, Thalheim, Bernhard, editor, and Libkin, Leonid, editor

Published
1998
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603. Semantics in spatial databases

Author

Kuijpers, Bart, Paredaens, Jan, Vandeurzen, Luc, Goos, Gerhard, editor, Hartmanis, Juris, editor, van Leeuwen, Jan, editor, Thalheim, Bernhard, editor, and Libkin, Leonid, editor

Published
1998
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604. Semantics of database transformations

Author

Davidson, Susan, Buneman, Peter, Kosky, Anthony, Goos, Gerhard, editor, Hartmanis, Juris, editor, van Leeuwen, Jan, editor, Thalheim, Bernhard, editor, and Libkin, Leonid, editor

Published
1998
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608. Quantitative Approaches to Information Protection

Author

Palamidessi, Catuscia, 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, Libkin, Leonid, editor, Kohlenbach, Ulrich, editor, and de Queiroz, Ruy, editor

Published
2013
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609. Counting in SPARQL Property Paths: Perspectives from Theory and Practice

Author

Martens, Wim, 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, Libkin, Leonid, editor, Kohlenbach, Ulrich, editor, and de Queiroz, Ruy, editor

Published
2013
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610. Natural Models of Homotopy Type Theory (Abstract)

Author

Awodey, Steve, 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, Libkin, Leonid, editor, Kohlenbach, Ulrich, editor, and de Queiroz, Ruy, editor

Published
2013
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611. Perspectives of Dynamic Complexity

Author

Schwentick, Thomas, 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, Libkin, Leonid, editor, Kohlenbach, Ulrich, editor, and de Queiroz, Ruy, editor

Published
2013
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612. Solutions and query rewriting in data exchange.

Author

Arenas, Marcelo, Barceló, Pablo, Fagin, Ronald, and Libkin, Leonid

Subjects
*MACHINE theory, *DATA structures, *SEARCH algorithms, *MATHEMATICAL models, *COMPUTER algorithms
Abstract

Abstract: Data exchange is the problem of taking data structured under a source schema and creating an instance of a target schema. Given a source instance, there may be many solutions – target instances that satisfy the constraints of the data exchange problem. Previous work has identified two classes of desirable solutions: canonical universal solutions, and their cores. Query answering in data exchange amounts to rewriting a query over the target schema to another query that, over a materialized target instance, gives the result that is semantically consistent with the source (specifically, the “certain answers”). Basic questions are then: (1) how do these solutions compare in terms of query rewriting? and (2) how can we determine whether a query is rewritable over a particular solution? Our goal is to answer these questions. Our first main result is that, in terms of rewritability by relational algebra queries, the core is strictly less expressive than the canonical universal solution, which in turn is strictly less expressive than the source. To develop techniques for proving queries non-rewritable, we establish structural properties of solutions; in fact they are derived from the technical machinery developed in the rewritability proofs. Our second result is that both the canonical universal solution and the core preserve the local structure of the data, and that every target query rewritable over any of these solutions cannot distinguish tuples whose neighborhoods in the source are similar. This gives us a first simple tool for checking whether a query is non-rewritable over the canonical universal solution or over the core. We also show that these tools generalize to arbitrary transformations that preserve the local structure of the data, and investigate an alternative semantics of query answering in data exchange. [Copyright &y& Elsevier]

Published
2013
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613. A Calculus of Chemical Systems

Author

Gordon Plotkin, Tannen, Val, Wong, Limsoon, Libkin, Leonid, Fan, Wenfei, Tan, Wang-Chiew, and Fourman, Michael

Subjects
Computer science, Semantics (computer science), Principle of compositionality, MathematicsofComputing_NUMERICALANALYSIS, Ode, Petri net, TheoryofComputation_MATHEMATICALLOGICANDFORMALLANGUAGES, TheoryofComputation_LOGICSANDMEANINGSOFPROGRAMS, Computer Science::Logic in Computer Science, Ordinary differential equation, ComputingMethodologies_SYMBOLICANDALGEBRAICMANIPULATION, Calculus, Homomorphism, Variety (universal algebra), Calculus of communicating systems
Abstract

We present the Calculus of Chemical Systems for the modular presentation of systems of chemical equations; it is intended to be a core calculus for rule-based modelling in systems biology. The calculus is loosely modelled after Milner’s Calculus of Communicating Systems, but with communication replaced by chemical reactions. We give a variety of compositional semantics for qualitative and quantitative versions of our calculus, employing a commutative monoid semantical framework. These semantics include (qualitative and quantitative) Petri nets, transition relations, ordinary differential equations (ODEs), and stochastic matrices. Standard semantics of Petri nets, whether of transition relations, ODEs, or stochastic matrices, fit within the framework as commutative monoid homomorphisms. We give complete equational axiomatisations and normal forms for all the semantics, and full abstraction results for the ODE and stochastic semantics. Definability can be characterised in some cases, as was already known for ODEs; other cases, including the stochastic one, remain open.

Published
2013

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