
Invited Talks
Invited talks will be given by:
Jürgen Dix
(University of Manchester, UK)
Tentative title: Computational Logic and MultiAgency
Georg Gottlob
(Vienna University of Technology, Austria)
Title: Declarative Information Extraction, Web Crawling and Recursive Wrapping with Lixto
Abstract:
Lixto is a system and method for the visual and interactive generation
of wrappers for Web pages under the supervision of a human developer,
for automatically extracting information from Web pages using such
wrappers, and for translating the extracted content into XML. In this
talk, we describe some advanced features of Lixto, such as disjunctive
pattern definitions, specialisation rules, and Lixto's capability of
collecting and aggregating information from several linked Web
pages. We illustrate these features with significant examples from the
commercial domain.
This will be a mixture between an invited talk and a system demo and will be given in conjunction with the system session.
Phokion Kolaitis
(University of California at Santa Cruz, USA)
Title: On the Complexity of Model Checking and Inference in Minimal Models
Abstract:
Every logical formalism gives rise to two fundamental algorithmic problems: model checking and inference. In propositional logic, the model checking problem is polynomialtime solvable, while the inference problem is coNPcomplete. In propositional circumscription, however, these problems have higher computational complexity, namely the model checking problem is coNPcomplete, while the inference problem is complete for the second level of the polynomial hierarchy PH.
In this talk, we survey recent results on the computational complexity
of restricted cases of these problems in the context of Schaefer's
framework of generalized satisfiability problems. These results
establish dichotomies in the complexity of the model checking problem
and the inference problem for propositional circumscription. They
yield a complete classification of the ``hard" and the ``easier" cases
of these problems and also provide efficiently checkable criteria that
tell apart the ``hard" cases from the ``easier" ones. This is joint
work with Lefteris M. Kirousis of the University of Patras.
Maurizio Lenzerini
(Università di Roma "La Sapienza", Italy)
Title: Data Integration Needs Reasoning
Abstract:
Data integration is the problem of combining the data residing at
different sources, and providing a unified view of these data, called
global schema, which can be queried by the user. The interest in this
kind of systems has been continuously growing in the last
years. However, the design of a data integration system is a very
complex task, and several issues remains open, including how to
express the relation between the global schema and the sources, and
how to process queries expressed on the global schema. In this talk,
we deal with these two problems, by presenting a logical framework for
data integration, and by discussing the various choices for both the
specification of a data integration system, and the design of query
answering methods. Also, we elaborate on the observation that, in
real world scenarios, the case of mutually inconsistent local
databases will be very common, and we present the basic ideas in order
to extend the integration framework with suitable nonmonotonic
reasoning features for dealing with this case.
Chiaki Sakama
(Wakayama University, Japan)
Tentative title: Nonmonotonic Inductive Logic Programming
Abstract:
Nonmonotonic logic programming (NMLP) and inductive logic programming (ILP)
are two important extensions of logic programming.
The former aims at representing incomplete knowledge and reasoning with
commonsense, while the latter targets the problem of inductive construction
of a general theory from examples and background knowledge.
NMLP and ILP thus have seemingly different motivations and goals, but
they have much in common in the background of problems, and
techniques developed in each field are related to one another.
In this talk, I present techniques for combining these two fields of
logic programming in the context of nonmonotonic inductive logic
programming (NMILP). I review recent results and problems to realize NMILP.
