9,623 research outputs found
Using Methods of Declarative Logic Programming for Intelligent Information Agents
The search for information on the web is faced with several problems, which
arise on the one hand from the vast number of available sources, and on the
other hand from their heterogeneity. A promising approach is the use of
multi-agent systems of information agents, which cooperatively solve advanced
information-retrieval problems. This requires capabilities to address complex
tasks, such as search and assessment of sources, query planning, information
merging and fusion, dealing with incomplete information, and handling of
inconsistency. In this paper, our interest is in the role which some methods
from the field of declarative logic programming can play in the realization of
reasoning capabilities for information agents. In particular, we are interested
in how they can be used and further developed for the specific needs of this
application domain. We review some existing systems and current projects, which
address information-integration problems. We then focus on declarative
knowledge-representation methods, and review and evaluate approaches from logic
programming and nonmonotonic reasoning for information agents. We discuss
advantages and drawbacks, and point out possible extensions and open issues.Comment: 66 pages, 1 figure, to be published in "Theory and Practice of Logic
Programming
Coherent Integration of Databases by Abductive Logic Programming
We introduce an abductive method for a coherent integration of independent
data-sources. The idea is to compute a list of data-facts that should be
inserted to the amalgamated database or retracted from it in order to restore
its consistency. This method is implemented by an abductive solver, called
Asystem, that applies SLDNFA-resolution on a meta-theory that relates
different, possibly contradicting, input databases. We also give a pure
model-theoretic analysis of the possible ways to `recover' consistent data from
an inconsistent database in terms of those models of the database that exhibit
as minimal inconsistent information as reasonably possible. This allows us to
characterize the `recovered databases' in terms of the `preferred' (i.e., most
consistent) models of the theory. The outcome is an abductive-based application
that is sound and complete with respect to a corresponding model-based,
preferential semantics, and -- to the best of our knowledge -- is more
expressive (thus more general) than any other implementation of coherent
integration of databases
Logical Foundations and Complexity of 4QL, a Query Language with Unrestricted Negation
The paper discusses properties of a DATALOG-like query language
4QL, originally outlined in [MS10]. Negated literals in heads of rules
naturally lead to inconsistencies. On the other hand, rules do not have to
attach meaning to some literals. Therefore 4QL is founded on a four-valued
semantics, employing the logic introduced in [MSV08, VMS09] with truth values:
'true', 'false', 'inconsistent' and 'unknown'. 4QL allows one to use rules with
negation in heads and bodies of rules, it is based on a simple and intuitive
semantics and provides uniform tools for "lightweight" versions of known forms
of nonmonotonic reasoning. In addition, 4QL is tractable as regards its data
complexity and captures PTIME queries. Even if DATALOG is known as
a concept for the last 30 years, to our best knowledge no existing approach
enjoys these properties.
In the current paper we: - investigate properties of well-supported models of
4QL - prove the correctness of the algorithm for computing well-supported
models - show that 4QL has PTIME data complexity and captures PTIME
Confidentiality-Preserving Data Publishing for Credulous Users by Extended Abduction
Publishing private data on external servers incurs the problem of how to
avoid unwanted disclosure of confidential data. We study a problem of
confidentiality in extended disjunctive logic programs and show how it can be
solved by extended abduction. In particular, we analyze how credulous
non-monotonic reasoning affects confidentiality.Comment: Paper appears in the Proceedings of the 19th International Conference
on Applications of Declarative Programming and Knowledge Management (INAP
2011
An Abductive Framework For Computing Knowledge Base Updates
This paper introduces an abductive framework for updating knowledge bases
represented by extended disjunctive programs. We first provide a simple
transformation from abductive programs to update programs which are logic
programs specifying changes on abductive hypotheses. Then, extended abduction,
which was introduced by the same authors as a generalization of traditional
abduction, is computed by the answer sets of update programs. Next, different
types of updates, view updates and theory updates are characterized by
abductive programs and computed by update programs. The task of consistency
restoration is also realized as special cases of these updates. Each update
problem is comparatively assessed from the computational complexity viewpoint.
The result of this paper provides a uniform framework for different types of
knowledge base updates, and each update is computed using existing procedures
of logic programming.Comment: Appeared in Theory and Practice of Logic Programming, vol. 3, no. 6,
200
Enhancing the expressive power of the U-Datalog language
U-Datalog has been developed with the aim of providing a set-oriented logical
update language, guaranteeing update parallelism in the context of a
Datalog-like language. In U-Datalog, updates are expressed by introducing
constraints (+p(X), to denote insertion, and [minus sign]p(X), to denote
deletion) inside Datalog rules. A U-Datalog program can be interpreted as a CLP
program. In this framework, a set of updates (constraints) is satisfiable if it
does not represent an inconsistent theory, that is, it does not require the
insertion and the deletion of the same fact. This approach resembles a very
simple form of negation. However, on the other hand, U-Datalog does not provide
any mechanism to explicitly deal with negative information, resulting in a
language with limited expressive power. In this paper, we provide a semantics,
based on stratification, handling the use of negated atoms in U-Datalog
programs, and we show which problems arise in defining a compositional
semantics.Comment: Appeared in Theory and Practice of Logic Programming, vol. 1, no. 1,
200
Analyzing Graph Transformation Systems through Constraint Handling Rules
Graph transformation systems (GTS) and constraint handling rules (CHR) are
non-deterministic rule-based state transition systems. CHR is well-known for
its powerful confluence and program equivalence analyses, for which we provide
the basis in this work to apply them to GTS. We give a sound and complete
embedding of GTS in CHR, investigate confluence of an embedded GTS, and provide
a program equivalence analysis for GTS via the embedding. The results confirm
the suitability of CHR-based program analyses for other formalisms embedded in
CHR.Comment: 45 pages, 11 figures, to appear in Theory and Practice of Logic
Programming (TPLP
Linear Models of Computation and Program Learning
We consider two classes of computations which admit taking linear
combinations of execution runs: probabilistic sampling and generalized
animation. We argue that the task of program learning should be more tractable
for these architectures than for conventional deterministic programs. We look
at the recent advances in the "sampling the samplers" paradigm in higher-order
probabilistic programming. We also discuss connections between partial
inconsistency, non-monotonic inference, and vector semantics.Comment: 13 pages; September 3, 2015 version; to appear in the Proceedings of
GCAI 2015, Tbilisi, Georgia, Oct.16-18, 201
Reduction of Many-valued into Two-valued Modal Logics
In this paper we develop a 2-valued reduction of many-valued logics, into
2-valued multi-modal logics. Such an approach is based on the contextualization
of many-valued logics with the introduction of higher-order Herbrand
interpretation types, where we explicitly introduce the coexistence of a set of
algebraic truth values of original many-valued logic, transformed as parameters
(or possible worlds), and the set of classic two logic values. This approach is
close to the approach used in annotated logics, but offers the possibility of
using the standard semantics based on Herbrand interpretations. Moreover, it
uses the properties of the higher-order Herbrand types, as their fundamental
nature is based on autoreferential Kripke semantics where the possible worlds
are algebraic truth-values of original many-valued logic. This autoreferential
Kripke semantics, which has the possibility of flattening higher-order Herbrand
interpretations into ordinary 2-valued Herbrand interpretations, gives us a
clearer insight into the relationship between many-valued and 2-valued
multi-modal logics. This methodology is applied to the class of many-valued
Logic Programs, where reduction is done in a structural way, based on the logic
structure (logic connectives) of original many-valued logics. Following this,
we generalize the reduction to general structural many-valued logics, in an
abstract way, based on Suszko's informal non-constructive idea. In all cases,
by using developed 2-valued reductions we obtain a kind of non truth-valued
modal meta-logics, where two-valued formulae are modal sentences obtained by
application of particular modal operators to original many-valued formulae.Comment: 27 page
AppLP: A Dialogue on Applications of Logic Programming
This document describes the contributions of the 2016 Applications of Logic
Programming Workshop (AppLP), which was held on October 17 and associated with
the International Conference on Logic Programming (ICLP) in Flushing, New York
City.Comment: David S. Warren and Yanhong A. Liu (Editors). 33 pages. Including
summaries by Christopher Kane and abstracts or position papers by M. Aref, J.
Rosenwald, I. Cervesato, E.S.L. Lam, M. Balduccini, J. Lobo, A. Russo, E.
Lupu, N. Leone, F. Ricca, G. Gupta, K. Marple, E. Salazar, Z. Chen, A. Sobhi,
S. Srirangapalli, C.R. Ramakrishnan, N. Bj{\o}rner, N.P. Lopes, A.
Rybalchenko, and P. Tara
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