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On the Enumeration Complexity of Unions of Conjunctive Queries [article]

Nofar Carmeli, Markus Kröll
2021 arXiv   pre-print
contain disequalities.  ...  Nevertheless, we prove that for several classes of queries, free-connexity fully captures the tractable UCQs.  ...  ACKNOWLEDGMENTS The authors are greatly thankful to Benny Kimelfeld for his advice. The work of Nofar Carmeli was supported by the Irwin and Joan Jacobs Fellowship and by the Google PhD Fellowship.  ... 
arXiv:1812.03831v5 fatcat:35apyblfrbgktocq7n5rbjpmeq

The HOM Problem is EXPTIME-Complete

Carles Creus, Adrià Gascón, Guillem Godoy, Lander Ramos
2016 SIAM journal on computing (Print)  
Tree automata with disequality and implicit HOM equality constraints.  ...  As a consequence, we obtain several EXPTIMEcompleteness results for problems on images of regular tree languages under tree homomorphisms, like set inclusion, regularity (HOM problem), and finiteness of  ...  The homomorphism (HOM) problem questions, for a given regular tree language L described by a tree automaton and a tree homomorphism H, whether H(L) is regular.  ... 
doi:10.1137/140999104 fatcat:yniqldd2wnegjfrgyuwxbmefjy

Approximately Counting Answers to Conjunctive Queries with Disequalities and Negations [article]

Jacob Focke, Leslie Ann Goldberg, Marc Roth, Stanislav Živný
2022 arXiv   pre-print
However, if there are neither disequalities nor negations, we prove the existence of an FPRAS for queries of bounded fractional hypertreewidth, strictly generalising the recently established FPRAS for  ...  We establish an exhaustive classification into tractable and intractable cases if φ is a conjunctive query with disequalities and negations: ∙ If there is a constant bound on the arity of φ, and if the  ...  Consequently by ( 2 ) there is a homomorphism h from A(ϕ) to B(ϕ, D) that extends τ and satisfies all disequalities in ∆(ϕ), that is, h(x i ) = h(x j ) for all {x i , x j } ∈ ∆(ϕ).  ... 
arXiv:2103.12468v2 fatcat:qlf52fkbnvcatnhasbvbhyhj3e

The HOM problem is decidable

Guillem Godoy, Omer Giménez
2013 Journal of the ACM  
For example, the tree lan- Tree homomorphisms are a powerful representation system.  ...  An automaton of this new class essentially recognizes the intersection of a tree automaton with disequality constraints and the image of a regular language through a tree homomorphism.  ...  In [10] it is shown that for any given regular language a and any given This is in contrast with top-down tree transducers: tree homomorphisms are also a particular case of top-down tree transducer,  ... 
doi:10.1145/2508028.2501600 fatcat:pe7p526xjzg3dpzhbhdrv4zu3y

The HOM problem is decidable

Guillem Godoy, Omer Giménez, Lander Ramos, Carme Àlvarez
2010 Proceedings of the 42nd ACM symposium on Theory of computing - STOC '10  
For example, the tree lan- Tree homomorphisms are a powerful representation system.  ...  An automaton of this new class essentially recognizes the intersection of a tree automaton with disequality constraints and the image of a regular language through a tree homomorphism.  ...  In [10] it is shown that for any given regular language a and any given This is in contrast with top-down tree transducers: tree homomorphisms are also a particular case of top-down tree transducer,  ... 
doi:10.1145/1806689.1806757 dblp:conf/stoc/GodoyGRA10 fatcat:rtuai6ewurahff6qu2y4w5zaou

Boolean Tensor Decomposition for Conjunctive Queries with Negation

Mahmoud Abo Khamis, Hung Q. Ngo, Dan Olteanu, Dan Suciu, Michael Wagner
2019 International Conference on Database Theory  
Its data complexity matches that of the InsideOut and PANDA algorithms for the positive subquery of the input query and is expressed in terms of the fractional hypertree width and the submodular width  ...  We show how to rewrite queries with negation on bounded-degree relations into equivalent conjunctive queries with not-all-equal (NAE) predicates, which are a multi-dimensional analog of disequality ( =  ...  The color-coding technique [8] underlies existing approaches to answering queries with disequalities [27, 9, 21] , the homomorphic embedding problem [14] , and motif finding and counting in computational  ... 
doi:10.4230/lipics.icdt.2019.21 dblp:conf/icdt/KhamisNOS19 fatcat:pntxmsf5crf3jgc3nz6qwlpktm

Automata on Infinite Trees with Equality and Disequality Constraints Between Siblings

Arnaud Carayol, Christof Löding, Olivier Serre
2016 Proceedings of the 31st Annual ACM/IEEE Symposium on Logic in Computer Science - LICS '16  
Roughly speaking we consider parity tree automata where some transitions are guarded and can be used only when the two direct sub-trees of the current node are equal/disequal.  ...  The first one is by Bogaert and Tison who considered a model of automata on finite ranked trees where one can check equality and disequality constraints between direct subtrees: they proved that this class  ...  language T of finite trees and a tree homomorphism h, whether the image h(T ) of T under h is a regular tree language.  ... 
doi:10.1145/2933575.2934504 dblp:conf/lics/CarayolLS16 fatcat:2niy35qp4bgevi6yqp5zxymxhe

Data Structure Specifications via Local Equality Axioms [chapter]

Scott McPeak, George C. Necula
2005 Lecture Notes in Computer Science  
We describe a complete decision procedure for axioms without disequalities, and practical heuristics for the full language.  ...  We describe a program verification methodology for specifying global shape properties of data structures by means of axioms involving predicates on scalar fields, pointer equalities, and pointer disequalities  ...  Acknowledgments This research was supported in part by NSF Grants CCR-0326577, and CCF-0524784.  ... 
doi:10.1007/11513988_47 fatcat:omztu7cb7rhubk7b453pwxth3u

Enumeration Complexity of Conjunctive Queries with Functional Dependencies [article]

Nofar Carmeli, Markus Kröll
2021 arXiv   pre-print
Further conclusions of our development include a dichotomy for enumeration with linear delay, and a dichotomy for CQs with disequalities.  ...  A known dichotomy classifies the acyclic self-join-free CQs into those that admit such enumeration, and those that do not.  ...  (⊥, b, c) ∈ S I . ⊓ ⊔ Fig. 1 1 Join tree T of H(Q + ) for head-paths of length greater than 2.  ... 
arXiv:1712.07880v2 fatcat:glrorkdwwrdqfkqdsigt4a5ha4

Boolean Tensor Decomposition for Conjunctive Queries with Negation [article]

Mahmoud Abo Khamis, Hung Q. Ngo, Dan Olteanu, Dan Suciu
2019 arXiv   pre-print
Its data complexity matches that of the best known algorithms for the positive subquery of the input query and is expressed in terms of the fractional hypertree width and the submodular width.  ...  We show how to rewrite queries with negation on bounded-degree relations into equivalent conjunctive queries with not-all-equal (NAE) predicates, which are a multi-dimensional analog of disequality (not-equal  ...  The color-coding technique [9] underlies existing approaches to answering queries with disequalities [11, 26, 37], the homomorphic embedding problem [18], and mo- tif finding and counting in computational  ... 
arXiv:1712.07445v5 fatcat:j7zth5dztnfmllt4w3dss5mqom

The Tractability of CSP Classes Defined by Forbidden Patterns

D. A. Cohen, M. C. Cooper, P. Creed, D. Marx, A. Z. Salamon
2012 The Journal of Artificial Intelligence Research  
The constraint satisfaction problem (CSP) is a general problem central to computer science and artificial intelligence.  ...  Recently, some authors have considered hybrid properties that restrict the constraint hypergraph and the relations simultaneously.  ...  Acknowledgments The authors acknowledge support from ANR Project ANR-10-BLAN-0210, EPSRC grants EP/F011776/1 and EP/I011935/1, ERC Starting Grant PARAMTIGHT (No. 280152), and EPSRC platform grant EP/F028288  ... 
doi:10.1613/jair.3651 fatcat:6tfaqcsoeffu7oxfwrkj426wz4

Majority constraints have bounded pathwidth duality

Víctor Dalmau, Andrei Krokhin
2008 European journal of combinatorics (Print)  
This implies that the constraint satisfaction problem for any fixed structure with a majority polymorphism is in NL.  ...  We show that such a problem is equivalent to deciding whether the given structure admits a homomorphism from an obstruction belonging to a certain class of structures of bounded pathwidth.  ...  Part of this work was done when both authors visited the Isaac Newton Institute for Mathematical Sciences, Cambridge. The financial support provided by the Institute is gratefully acknowledged.  ... 
doi:10.1016/j.ejc.2007.11.020 fatcat:5obi63teijbqhmdhw5kzvepvn4

Tractable Lineages on Treelike Instances

Antoine Amarilli, Pierre Bourhis, Pierre Senellart
2016 Proceedings of the 35th ACM SIGMOD-SIGACT-SIGAI Symposium on Principles of Database Systems - PODS '16  
By contrast, we can strengthen the previous dichotomy to lineages, and show that there are even UCQs with disequalities that have superpolynomial OBDDs on all unbounded-treewidth graph classes; we give  ...  This dichotomy relies on recent polynomial bounds on the extraction of planar graphs as minors, and implies lower bounds in non-probabilistic settings, for query evaluation and match counting in subinstance-closed  ...  We also thank the anonymous reviewers of PODS 2016 for their valuable comments, in particular for strengthening Theorem 9.7 to tree-depth.  ... 
doi:10.1145/2902251.2902301 dblp:conf/pods/AmarilliBS16 fatcat:skanmavk2vfrfgop3wqq3ebpoe

Tractable Reasoning in a Fragment of Separation Logic [chapter]

Byron Cook, Christoph Haase, Joël Ouaknine, Matthew Parkinson, James Worrell
2011 Lecture Notes in Computer Science  
In 2004, Berdine, Calcagno and O'Hearn introduced a fragment of separation logic that allows for reasoning about programs with pointers and linked lists.  ...  Entailment between two such formulae then reduces to a graph homomorphism problem. We also discuss natural syntactic extensions that render entailment intractable.  ...  We would like to thank Nikos Gorogiannis for interesting and helpful discussions and the anonymous referees for helpful suggestions on how to improve the presentation of the paper.  ... 
doi:10.1007/978-3-642-23217-6_16 fatcat:wrjr6muoofebjjjbwkfbtjoccu

Tree pattern query minimization

S. Amer-Yahia, S. Cho, L.V.S. Lakshmanan, D. Srivastava
2002 The VLDB journal  
(based on homomorphism techniques), and reduction.  ...  Tree patterns form a natural basis to query treestructured data such as XML and LDAP.  ...  Acknowledgements We would like to thank Dan Suciu and the reviewers of this paper for their insightful comments and suggestions, which helped improve this paper substantially.  ... 
doi:10.1007/s00778-002-0076-7 fatcat:5cxp6mi27bewhi4milnij3zdfu
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