ICLP on Wednesday

Detailed program
Wednesday July 31st, 2002
See also the unified by-slot program

Sessions take place in auditorium 4 unless otherwise indicated.

Session 9: World Wide Web

Chair: Peter Stuckey

09:00-10:00  Stefan Decker, Stanford U, USA
Invited talk: Logic databases on the semantic web: Challenges and opportunities
Until now, the Web has mainly designed for direct human consumption. The next step in the evolution, dubbed the "Semantic Web", aims at machine-processable information, enabling intelligent services such as information brokers, search agents, information filters, and direct B2B communication, which offers greater functionality and interoperability than the current stand-alone services.
The development of the Semantic Web creates opportunities and challenges for logic databases. Languages need to be developed which allow us to specify data transformations for various data models. Efficient query and inference techniques have to be developed. Technologies developed by the Logic Programming and Deductive Database Community can help to built the Semantic Web by overcoming these problems.

10:00-10:30  François Bry, U Munich, Germany
Sebastian Schaffert, U Munich, Germany
Towards a declarative query and transformation language for XML and semistructured data: Simulation unification
The growing importance of XML as a data interchange standard demands languages for data querying and transformation. Since the mid 90es, several such languages have been proposed that are inspired from functional languages (such as XSLT) and/or database query languages (such as XQuery). This paper addresses applying logic programming concepts and techniques to designing a declarative, rule-based query and transformation language for XML and semistructured data.
The paper first introduces issues specific to XML and semistructured data such as the necessity of flexible "query terms" and of "construct terms". Then, it is argued that logic programming concepts are particularly appropriate for a declarative query and transformation language for XML and semistructured data. Finally, a new form of unification, called "simulation unification", is proposed for answering "query terms", and it is illustrated on examples.

Session 10: Theory

Chair: Michael Maher

11:00-11:30  Brigitte Pientka, Carnegie Mellon U, USA
A proof-theoretic foundation for tabled higher-order logic programming
Higher-order logic programming languages such as Elf extend first-order logic programming in two ways: first-order terms are replaced with (dependently) typed λ-terms and the body of clauses may contain implication and universal quantification. In this paper, we describe tabled higher-order logic programming where some redundant computation is eliminated by memoizing sub-computation and re-using its result later. This work extends Tamaki and Sato's search strategy based on memoization to the higher-order setting. We give a proof-theoretic characterization of tabling based on uniform proofs and prove soundness of the resulting interpreter. Based on it, we have implemented a prototype of a tabled logic programming interpreter for Elf.

11:30-12:00  Sorin Craciunescu, INRIA Rocquencourt, France
Proving the equivalence of CLP programs
This paper presents two proof systems for the equivalence of programs. The language concerned is CLP to which the universal quantifier is added (CLP∀). Both systems are based on first order classical logic.
The first uses an induction rule and allows one to prove that the set of finite successes of a program is included in another program's corresponding set. The second uses a coinduction rule for proving the inclusion of the sets of infinite successes which contain the finite successes.
Finally we show that the proof systems are equivalent under some natural conditions.

12:00-12:30  Paola Bruscoli, Dresden U of Techn., Germany
A purely logical account of sequentiality in proof search
A strict correspondence between the proof-search space of a logical formal system and computations in a simple process algebra is established. Sequential composition in the process algebra corresponds to a logical relation in the the formal system - in the sense our approach is purely logical, no axioms or encodings are involved. The process algebra is a minimal restriction of CCS to parallel and sequential composition; the logical system is a minimal extension of multiplicative linear logic. This way we get the first purely logical account of sequentiality in proof search. Since we restrict attention to a small meaningful fragment, which is then of very broad interest, our techniques should become a common basis for several possible extensions. In particular, we argue about this work being the first step in a two-step research for capturing most of CCS in a purely logical fashion.

Session 11: Invited Tutorial

14:00-15:30  Miroslaw Truszczynski, U Kentucky, USA
Invited tutorial: Answer set programming

Session 12: Stable Models and Answer Sets I

Chair: Mirek Truszczynski

16:00-16:30  Katsumi Inoue, Kobe U, Japan
Chiaki Sakama, Wakayama U, Japan
Disjunctive explanations
Abductive logic programming has been widely used to declaratively specify a variety of problems in AI including updates in data and knowledge bases, belief revision, diagnosis, causal theory, and default reasoning. One of the most significant issues in abductive logic programming is to develop a reasonable method for knowledge assimilation, which incorporates obtained explanations into the current knowledge base. This paper offers a solution to this problem by considering disjunctive explanations whenever multiple explanations exist. Disjunctive explanations are then to be assimilated into the knowledge base so that the assimilated program preserves all and only minimal answer sets from the collection of all possible updated programs. We describe a new form of abductive logic programming which deals with disjunctive explanations in the framework of extended abduction. The proposed framework can be well applied to view updates in disjunctive databases.

18:00-19:30  ICLP boat trip excursion; leaving from *Nyhavn*

Room: Nyhavn

Conference dinner

Joint with TABLEAUX
Room: Restaurant Luftkastellet

19:30-20:30  Banquet

20:30-22:00  Veronica Dahl, Simon Fraser U, Canada
Banquet speaker: Title TBA