28 research outputs found
Magic Sets for Disjunctive Datalog Programs
In this paper, a new technique for the optimization of (partially) bound
queries over disjunctive Datalog programs with stratified negation is
presented. The technique exploits the propagation of query bindings and extends
the Magic Set (MS) optimization technique.
An important feature of disjunctive Datalog is nonmonotonicity, which calls
for nondeterministic implementations, such as backtracking search. A
distinguishing characteristic of the new method is that the optimization can be
exploited also during the nondeterministic phase. In particular, after some
assumptions have been made during the computation, parts of the program may
become irrelevant to a query under these assumptions. This allows for dynamic
pruning of the search space. In contrast, the effect of the previously defined
MS methods for disjunctive Datalog is limited to the deterministic portion of
the process. In this way, the potential performance gain by using the proposed
method can be exponential, as could be observed empirically.
The correctness of MS is established thanks to a strong relationship between
MS and unfounded sets that has not been studied in the literature before. This
knowledge allows for extending the method also to programs with stratified
negation in a natural way.
The proposed method has been implemented in DLV and various experiments have
been conducted. Experimental results on synthetic data confirm the utility of
MS for disjunctive Datalog, and they highlight the computational gain that may
be obtained by the new method w.r.t. the previously proposed MS methods for
disjunctive Datalog programs. Further experiments on real-world data show the
benefits of MS within an application scenario that has received considerable
attention in recent years, the problem of answering user queries over possibly
inconsistent databases originating from integration of autonomous sources of
information.Comment: 67 pages, 19 figures, preprint submitted to Artificial Intelligenc
Constraint-based Query Distribution Framework for an Integrated Global Schema
Distributed heterogeneous data sources need to be queried uniformly using
global schema. Query on global schema is reformulated so that it can be
executed on local data sources. Constraints in global schema and mappings are
used for source selection, query optimization,and querying partitioned and
replicated data sources. The provided system is all XML-based which poses query
in XML form, transforms, and integrates local results in an XML document.
Contributions include the use of constraints in our existing global schema
which help in source selection and query optimization, and a global query
distribution framework for querying distributed heterogeneous data sources.Comment: The Proceedings of the 13th INMIC 2009), Dec. 14-15, 2009, Islamabad,
Pakistan. Pages 1 - 6 Print ISBN: 978-1-4244-4872-2 INSPEC Accession Number:
11072575 Date of Current Version : 15 January 201
Some DLV Applications for Knowledge Management
Abstract. Even if the industrial exploitation of the DLV system has started very recently, DLV already has a history of applications on the industrial level. The most valuable applications from a commercial viewpoint are those in the area of Knowledge Management. They have been realized by the company EXEURA s.r.l. -a spin-off company of the University of Calabria having a branch also in Chicago -with the support of the DLVSYSTEM s.r.l.. DLV applications in this area have not been realized directly, but through some specializations of DLV into Knowledge Management (KM) products for Text Classification, Information Extraction, and Ontology Representation and Reasoning. After briefly describing these KM products, we report on their recently-released successful applications
On the evolution of the instance level of DL-lite knowledge bases
Recent papers address the issue of updating the instance level of knowledge
bases expressed in Description Logic following a model-based approach. One of
the outcomes of these papers is that the result of updating a knowledge base K
is generally not expressible in the Description Logic used to express K. In
this paper we introduce a formula-based approach to this problem, by revisiting
some research work on formula-based updates developed in the '80s, in
particular the WIDTIO (When In Doubt, Throw It Out) approach. We show that our
operator enjoys desirable properties, including that both insertions and
deletions according to such operator can be expressed in the DL used for the
original KB. Also, we present polynomial time algorithms for the evolution of
the instance level knowledge bases expressed in the most expressive Description
Logics of the DL-lite family
Unit Testing in ASPIDE
Answer Set Programming (ASP) is a declarative logic programming formalism,
which is employed nowadays in both academic and industrial real-world
applications. Although some tools for supporting the development of ASP
programs have been proposed in the last few years, the crucial task of testing
ASP programs received less attention, and is an Achilles' heel of the available
programming environments.
In this paper we present a language for specifying and running unit tests on
ASP programs. The testing language has been implemented in ASPIDE, a
comprehensive IDE for ASP, which supports the entire life-cycle of ASP
development with a collection of user-friendly graphical tools for program
composition, testing, debugging, profiling, solver execution configuration, and
output-handling.Comment: 12 pages, 4 figures, Proceedings of the 25th Workshop on Logic
Programming (WLP 2011