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1

Coordinating multiple rescue robots

Białek Ł., Szałas A., Borkowski A., Gnatowski M., Borkowska M. M., Dunin-Kęplicz B., Szklarski J.

Prace Naukowe Politechniki Warszawskiej. Elektronika

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2014

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z. 194, t. 1

185--194

EN

The paper reports initial results on modeling and simulating cooperation of rescue robots. Our aim is to investigate the efficiency of the "first simulate then act" paradigm for rescue operations undertaken by multiple mobile robots, assuming that information about the environment can be incomplete and partially inconsistent. to deal with ignorance and contradictions we adopt a non-standard logic in the infrrence engine. To demonstrate feasibility of our approach we present the architecture of the developed simulator and results of experiments done so far.

2

Negatywna informacja w języku regułowym 4QL

Małuszyński J., Szałas A.

Zeszyty Naukowe Warszawskiej Wyższej Szkoły Informatyki

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2013

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nr 9

7--14

EN

Problematyka negatywnej informacji w językach regułowych jest zasadnicza z punktu widzenia dużej liczby aplikacji. Była ona rozważana w rozszerzeniach języków zapytań w dedukcyjnych bazach danych, opartych na wnioskowaniach niemonotonicznych, początkowo wynikających z założenia o zamkniętym świecie CWA (Closed World Assumption). W wielu zastosowaniach, w tym związanych z Semantycznym Internetem i robotyką, założenie CWA nie jest właściwe i zwykle przyjmuje się w nich założenie o świecie otwartym OWA (Open World Assumption). W niniejszym artykule omawiamy nowe podejście do tego problemu, przedstawione w [2] [3] [4], gdzie zaproponowaliśmy język regułowy 4QL w stylu Datalogu, jednak bez ograniczeń na wystąpienie negacji. Język ma architekturę warstwową. Najniższe warstwy 4QL, oparte na OWA, są w pełni monotoniczne. W celu zmniejszenia stref niewiedzy/sprzeczności w [2] [3] wprowadzono proste konstrukcje pozwalające na wyrażanie mechanizmów wnioskowań niemonotonicznych, w tym umożliwiających rozwiązywanie sprzeczności, użycie lokalnych domknięć świata (a więc także CWA) oraz różnych form wnioskowań przez domniemania. Obliczanie zapytań w 4QL ma złożoność wielomianową ze względu na rozmiar bazy danych.

XX

The problem of negative information in rule languages is crucial in many applications. It has been addressed in extensions of query languages in deductive databases, based on nonmonotonic logics initially derived from the Closed World Assumption (CWA). In many applications, including Semantic Web technologies and robotics systems, CWA is not necessarily applicable and developments in these fields usually follow the Open World Assumption (OWA). In this paper we summarize a novel approach to the problem reported in [2] [3] [4], where we proposed a DATALOG-like language 4QL with unrestricted negation. The language supports a layered architecture. The monotonic layer of 4QL, based on OWA, is fully monotonic. To reduce the unknown/inconsistent zones, in [2] [3] we have introduced simple constructs which allow one to express various mechanisms of nonmonotonic reasoning. In particular, this provides means for application-specific disambiguation of inconsistent information, the use of Local CWA (thus also CWA, if needed), and various forms of default reasoning. Query evaluation in 4QL is still tractable as regards its data complexity.

3

Automated Generation of Logical Constraints on Approximation Spaces Using Quantifier Elimination

Doherty P., Szałas A.

Fundamenta Informaticae

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2013

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Vol. 127, nr 1-4

135--149

EN

This paper focuses on approximate reasoning based on the use of approximation spaces. Approximation spaces and the approximated relations induced by them are a generalization of the rough set-based approximations of Pawlak. Approximation spaces are used to define neighborhoods around individuals and rough inclusion functions. These in turn are used to define approximate sets and relations. In any of the approaches, one would like to embed such relations in an appropriate logical theory which can be used as a reasoning engine for specific applications with specific constraints. We propose a framework which permits a formal study of the relationship between properties of approximations and properties of approximation spaces. Using ideas from correspondence theory, we develop an analogous framework for approximation spaces. We also show that this framework can be strongly supported by automated techniques for quantifier elimination.

4

Semantic Web in a Nutshell

Szałas A.

Zeszyty Naukowe Warszawskiej Wyższej Szkoły Informatyki

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2011

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nr 6

14--19

EN

The paper outlines selected topics related to Semantic Web. We start with problems with the use of current web search engines. Next, we discuss the architecture and basic concepts of Semantic Web whose central ideas focus around ontologies. We show the role of logics in the specification and verification of ontologies as well as reasoning about them. We mainly concentrate on rule languages. In particular we discuss the 4QL query language supplying the user with simple, yet powerful constructs for filling gaps in missing knowledge as well as for disambiguation of inconsistencies.

PL

Artykuł zarysowuje wybrane zagadnienia związane z Semantycznym Internetem. Wychodząc od problemów rozwiązań stosowanych we współczesnych wyszukiwarkach, traktuje o architekturze i zasadniczych koncepcjach Semantycznego Internetu, którego kluczowym pojęciem są ontologie. Tekst omawia miejsce logik w specyfikacji i weryfikacji ontologii, a także wnioskowaniu o nich, koncentrując się przede wszystkim na językach regułowych, w tym na języku 4QL, dostarczającym prostych konstrukcji umożliwiających reakcję na niepełną i/lub sprzeczną informację.

5

Checking Consistency of an ABox w.r.t. Global Assumptions in PDL

Nguyen L.A. L.A., Szałas A.

Fundamenta Informaticae

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2010

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Vol. 102, nr 1

97-113

EN

We reformulate Pratt's tableau decision procedure of checking satisfiability of a set of formulas in PDL. Our formulation is simpler and its implementation is more direct. Extending the method we give the first EXPTIME (optimal) tableau decision procedure not based on transformation for checking consistency of an ABox w.r.t. a TBox in PDL (here, PDL is treated as a description logic). We also prove a new result that the data complexity of the instance checking problem in PDL is coNP-complete.

6

A Framework for Graded Beliefs, Goals and Intentions

Dunin-Kęplicz B., Nguyen L.A. L.A., Szałas A.

Fundamenta Informaticae

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2010

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Vol. 100, nr 1/4

53-76

EN

In natural language we often use graded concepts, reflecting different intensity degrees of certain features. Whenever such concepts appear in a given real-life context, they need to be appropriately expressed in its models. In this paper, we provide a framework which allows for extending the BGI model of agency by grading beliefs, goals and intentions. We concentrate on TEAMLOG [6, 7, 8, 9, 12] and provide a complexity-optimal decision method for its graded version TEAMLOGK by translating it into CPDL_reg (propositional dynamic logic with converse and "inclusion axioms" characterized by regular languages). We also develop a tableau calculus which leads to the first EXPTIME (optimal) tableau decision procedure for CPDL_reg. As CPDL_reg is suitable for expressing complex properties of graded operators, the procedure can also be used as a decision tool for other multiagent formalisms.

7

Modeling and Reasoning with Paraconsistent Rough Sets

Vitória A., Małuszyński J., Szałas A.

Fundamenta Informaticae

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2009

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Vol. 97, nr 4

405-438

EN

We present a language for defining paraconsistent rough sets and reasoning about them. Our framework relates and brings together two major fields: rough sets [23] and paraconsistent logic programming [9]. To model inconsistent and incomplete information we use a four-valued logic. The language discussed in this paper is based on ideas of our previous work [21, 32, 22] developing a four-valued framework for rough sets. In this approach membership function, set containment and set operations are four-valued, where logical values are t (true), f (false), i (inconsistent) and u (unknown). We investigate properties of paraconsistent rough sets as well as develop a paraconsistent rule language, providing basic computational machinery for our approach.

8

A Correspondence Framework between Three-Valued Logics and Similarity-Based Approximate Reasoning

Doherty P., Szałas A.

Fundamenta Informaticae

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2007

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Vol. 75, nr 1-4

179-193

EN

This paper focuses on approximate reasoning based on the use of similarity spaces. Similarity spaces and the approximated relations induced by them are a generalization of the rough set-based approximations of Pawlak [17, 18]. Similarity spaces are used to define neighborhoods around individuals and these in turn are used to define approximate sets and relations. In any of the approaches, one would like to embed such relations in an appropriate logic which can be used as a reasoning engine for specific applications with specific constraints. We propose a framework which permits a formal study of the relationship between approximate relations, similarity spaces and three-valued logics. Using ideas from correspondence theory for modal logics and constraints on an accessibility relation, we develop an analogous framework for three-valued logics and constraints on similarity relations. In this manner, we can provide a tool which helps in determining the proper three-valued logical reasoning engine to use for different classes of approximate relations generated via specific types of similarity spaces. Additionally, by choosing a three-valued logic first, the framework determines what constraints would be required on a similarity relation and the approximate relations induced by it. Such information would guide the generation of approximate relations for specific applications.

9

O pewnych zastosowaniach eliminacji kwantyfikatorów w robotyce

Szałas A.

Zeszyty Naukowe Warszawskiej Wyższej Szkoły Informatyki

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2006

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nr 1

139--147

PL

Niniejszy wykład zarysowuje w popularyzującym ujęciu wybrane zagadnieniom efektywnego wnioskowania prowadzonego w warunkach, w których mamy do czynienia z wiedzą niepełną, niepewną i silnie zaszumioną, gdy trzeba poradzić sobie ze złej jakości danymi, w tym bieżącymi odczytami pomiarów, obrazami z kamer itp. Wykład jest oparty o rozwiązania opracowane dla potrzeb bezzałogowych helikopterów (rzeczywiście wykonujących loty bezzałogowe w kontrolowanych warunkach poligonowych). W szczególności naszkicowane będą dość subtelne formy wnioskowania wykorzystujące niebanalne techniki logiczne, drastycznie obniżające złożoność wnioskowania w dużej klasie teorii spotykanych w praktyce.

EN

The current lecture provides a popular overview of selected topics concerning efficient reasoning dealing with incomplete and noisy data of bad quality, collected from sensors and video cameras. The lecture is based on solutions worked out for autonomous aerial vehicles and test flights over a rescure training area in Revinge (Sweden). In particular we sketch rather subtle forms of reasoning based on nontrivial logical methods substantially deceasing the complexity of reasoning in a large class of theories applied in practice.

10

Towards a Framework for Approximate Ontologies

Doherty P., Grabowski M., Łukaszewicz W., Szałas A.

Fundamenta Informaticae

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2003

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Vol. 57, nr 2-4

147--165

EN

Currently, there is a great deal of interest in developing tools for the generation and use of ontologies on the WWW. These knowledge structures are considered essential to the success of the semantic web, the next phase in the evolution of the WWW. Much recent work with ontologies assumes that the concepts used as building blocks are crisp as opposed to approximate. It is a premise of this paper that approximate concepts and ontologies will become increasingly more important as the semantic web becomes a reality. We propose a framework for specifying, generating and using approximate ontologies. More specifically, (1) a formal framework for defining approximate concepts, ontologies and operations on approximate concepts and ontologies is presented. The framework is based on intuitions from rough set theory; (2) algorithms for automatically generating approximate ontologies from traditional crisp ontologies or from large data sets together with additional knowledge are presented. The knowledge will generally be related to similarity measurements between individual objects in the data sets, or constraints of a logical nature which rule out particular constellations of concepts and dependencies in generated ontologies. The techniques for generating approximate ontologies are parameterizable. The paper provides specific instantiations and examples.

11

Meta-queries on deductive databases

Doherty P., Kachniarz J., Szałas A.

Fundamenta Informaticae

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1999

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Vol. 40, Nr 1

17-30

EN

We introduce the notion of a meta-query on relational databases and a technique which can be used to represent and solve a number of interesting problems from the area of knowledge representation using logic. The technique is based on the use of quantifier elimination and may also be used to query relational databases using a declarative query language called SHQL (Semi-Horn Query Language), introduced in [6]. SHQL is a fragment of classical first-order predicate logic and allows us to define a query without supplying its explicit definition. All SHQL queries to the database can be processed in polynomial time (both on the size of the input query and the size of the database). We demonstrate the use of the technique in problem solving by structuring logical puzzles from the Knights and Knaves domain as SHQL meta-queries on relational databases. We also provide additional examples demonstrating the flexibility of the technique. We conclude with a description of a newly developed software tool, The Logic Engineer, which aids in the description of algorithms using transformation and reduction techniques such as those applied in the meta-querying approach

12

General Domain Circumscription and its effective reductions

Doherty P., Łukaszewicz W., Szałas A.

Fundamenta Informaticae

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1998

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Vol. 36, nr 1

23-55

EN

We first define general domain circumscription (GDC) and provide it with a semantics. GDA subsumes existing domain circumscription proposals in that it allow varying of arbitrary predicates, functions, or constants, to maximize the minimization of the domain of a theory. We then show that for the class of semi-universal theories without function symbols, that the domain circumscription of such theories can be constructively reduced to logically equivalent first-order theories by using an extension of the DLS algorithm, previously proposed by the authors for reducing second-order-formulas. We also show that for a certain class of domain circumscribed theories, that any arbitrary second-order circumscription policy applied to these theories is guaranteed to be reducible to a logically equivalent first-order theory. In the case of semi-universal theories with functions and arbitrary theories which are not separated, we provide additional results, which although not guaranteed to provide reductions in all cases, do provide reductions in some cases. These results are based on the use of fixpoint reductions.