241 research outputs found
The complexity of dominating set reconfiguration
Suppose that we are given two dominating sets and of a graph
whose cardinalities are at most a given threshold . Then, we are asked
whether there exists a sequence of dominating sets of between and
such that each dominating set in the sequence is of cardinality at most
and can be obtained from the previous one by either adding or deleting
exactly one vertex. This problem is known to be PSPACE-complete in general. In
this paper, we study the complexity of this decision problem from the viewpoint
of graph classes. We first prove that the problem remains PSPACE-complete even
for planar graphs, bounded bandwidth graphs, split graphs, and bipartite
graphs. We then give a general scheme to construct linear-time algorithms and
show that the problem can be solved in linear time for cographs, trees, and
interval graphs. Furthermore, for these tractable cases, we can obtain a
desired sequence such that the number of additions and deletions is bounded by
, where is the number of vertices in the input graph
Algorithmic aspects of disjunctive domination in graphs
For a graph , a set is called a \emph{disjunctive
dominating set} of if for every vertex , is either
adjacent to a vertex of or has at least two vertices in at distance
from it. The cardinality of a minimum disjunctive dominating set of is
called the \emph{disjunctive domination number} of graph , and is denoted by
. The \textsc{Minimum Disjunctive Domination Problem} (MDDP)
is to find a disjunctive dominating set of cardinality .
Given a positive integer and a graph , the \textsc{Disjunctive
Domination Decision Problem} (DDDP) is to decide whether has a disjunctive
dominating set of cardinality at most . In this article, we first propose a
linear time algorithm for MDDP in proper interval graphs. Next we tighten the
NP-completeness of DDDP by showing that it remains NP-complete even in chordal
graphs. We also propose a -approximation
algorithm for MDDP in general graphs and prove that MDDP can not be
approximated within for any unless NP
DTIME. Finally, we show that MDDP is
APX-complete for bipartite graphs with maximum degree
Is post orthognathic maxillary sinusitis related to sino-nasal anatomical alterations?
Le Fort I osteotomies have been used for more than five decades, but their impact on nasal and paranasal cavities physiology, has not been studied deeply. In this paper we want to analyse the possible correlation between post-orthognathic findings and prevalence of sinusitis which require surgical treatment. A retrospective cohort study was designed in 2017; the study was designed and carried out in the Verona University maxillo-facial department, a referral centre for orthognathic surgery. The study population is made of 64 patients that underwent orthognathic surgery (To treat class II or III malocclusion) between 2010 and 2015. Inclusion criteria were the availability of a Cone Beam Computed Tomography (CBCT) before surgery and one between 12 and 24 months after orthognathic surgery. Exclusion criteria were smoking habit and previous orthognathic procedures. During follow-up time prevalence of sinusitis was 18.5% and some patients required a secondary surgery to treat sinusitis. Surgery induced anatomic alterations were frequent in patients with sinusitis, sings and symptoms of sinusitis show positive correlation with anatomic alterations
A SAT-based System for Consistent Query Answering
An inconsistent database is a database that violates one or more integrity
constraints, such as functional dependencies. Consistent Query Answering is a
rigorous and principled approach to the semantics of queries posed against
inconsistent databases. The consistent answers to a query on an inconsistent
database is the intersection of the answers to the query on every repair, i.e.,
on every consistent database that differs from the given inconsistent one in a
minimal way. Computing the consistent answers of a fixed conjunctive query on a
given inconsistent database can be a coNP-hard problem, even though every fixed
conjunctive query is efficiently computable on a given consistent database.
We designed, implemented, and evaluated CAvSAT, a SAT-based system for
consistent query answering. CAvSAT leverages a set of natural reductions from
the complement of consistent query answering to SAT and to Weighted MaxSAT. The
system is capable of handling unions of conjunctive queries and arbitrary
denial constraints, which include functional dependencies as a special case. We
report results from experiments evaluating CAvSAT on both synthetic and
real-world databases. These results provide evidence that a SAT-based approach
can give rise to a comprehensive and scalable system for consistent query
answering.Comment: 25 pages including appendix, to appear in the 22nd International
Conference on Theory and Applications of Satisfiability Testin
ERBlox: Combining Matching Dependencies with Machine Learning for Entity Resolution
Entity resolution (ER), an important and common data cleaning problem, is
about detecting data duplicate representations for the same external entities,
and merging them into single representations. Relatively recently, declarative
rules called matching dependencies (MDs) have been proposed for specifying
similarity conditions under which attribute values in database records are
merged. In this work we show the process and the benefits of integrating three
components of ER: (a) Classifiers for duplicate/non-duplicate record pairs
built using machine learning (ML) techniques, (b) MDs for supporting both the
blocking phase of ML and the merge itself; and (c) The use of the declarative
language LogiQL -an extended form of Datalog supported by the LogicBlox
platform- for data processing, and the specification and enforcement of MDs.Comment: To appear in Proc. SUM, 201
A STUDY OF THE IMPACT OF LAND USE AND OCCUPATION ON BASIN WATER QUALITY THROUGH MULTIVARIATE STATISTICS
Rainbow domination and related problems on some classes of perfect graphs
Let and let be a graph. A function is a rainbow function if, for every vertex with
, . The rainbow domination number
is the minimum of over all rainbow
functions. We investigate the rainbow domination problem for some classes of
perfect graphs
Answers that Have Integrity
[EN] Answers to queries in possibly inconsistent databases may
not have integrity. We formalize ‘has integrity’ on the basis of a definition
of ‘causes’. A cause of an answer is a minimal excerpt of the database
that explains why the answer has been given. An answer has integrity if
one of its causes does not overlap with any cause of integrity violation.Supported by FEDER and the Spanish grants TIN2009-14460-C03, TIN2010-17139.Decker, H. (2011). Answers that Have Integrity. Lecture Notes in Computer Science. 6834:54-72. https://doi.org/10.1007/978-3-642-23441-5S5472683
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