Fundamenta Informaticae - Volume 32, issue 2

Authors: Komorowski, J. | Raś, Z.W.

Article Type: Other

DOI: 10.3233/FI-1997-32207

Citation: Fundamenta Informaticae, vol. 32, no. 2, pp. i-i, 1997

Authors: Chakraborty, Mihir K. | Orlowska, Ewa

Article Type: Research Article

Abstract: A semantics of identity inspired by rough set modeling of uncertainty is proposed and the underlying substitutivity principles are presented. A survey of some theories of identity is given, in particular, an interpretation of identity in E-unification theory, some many-valued logics and some algebraic theories.

DOI: 10.3233/FI-1997-32201

Citation: Fundamenta Informaticae, vol. 32, no. 2, pp. 107-120, 1997

Authors: Gaasterland, Terry | Lobo, Jorge

Article Type: Research Article

Abstract: This paper presents a rigorous methodology for using annotated logic programming techniques to handle user preferences and needs in answering database queries. Two alternative transformations turn a database program into a new program that returns answers to queries according to qualitative labels. The two transformations have different semantics and are each appropriate in different situations. We have modified the standard definitions of annotated logic programs to handle user needs and preferences in databases. In the formalism, the user provides a lattice of domain-independent values that define preferences and needs and a set of domain specific user constraints qualified with lattice …values. After the original database and the user constraints have been transformed into a new annotated deductive database, query-answering procedures for deductive databases are used, with minor modifications, to obtain annotated answers to queries. Because preference declaration is separated from data representation and management, preferences can be easily altered without touching the database. The resulting query language allows users to ask for answers at different preference levels. Show more

DOI: 10.3233/FI-1997-32202

Citation: Fundamenta Informaticae, vol. 32, no. 2, pp. 121-137, 1997

Authors: Marek, V. Wiktor | Nerode, Anil | Remmel, Jeffrey B.

Article Type: Research Article

Abstract: Normal default logic, the fragment of default logic obtained by restricting defaults to rules of the form α:Mβ/β, is the most important and widely studied part of default logic. In [20], we proved a basis theorem for extensions of recursive propositional logic normal default theories and hence for finite predicate logic normal default theories. That is, we proved that every recursive propositional normal default theory possesses an extension which is r.e. in 0′. Here we show that this bound is tight. Specifically, we show that for every r.e. set A and every set B r.e. in A there is a …recursive normal default theory 〈D, W〉 with a unique extension which is Turing-equivalent to A ⌖ B. A similar result holds for finite predicate logic normal default theories. Show more

DOI: 10.3233/FI-1997-32203

Citation: Fundamenta Informaticae, vol. 32, no. 2, pp. 139-147, 1997

Authors: P$\check{A}$un, Gheorghe | Polkowski, Lech | Skowron, Andrzej

Article Type: Research Article

Abstract: We investigate here the possibility of approximating a language starting from a partial knowledge of its strings. This is understood as the possibility to read only a bounded part of a string: a prefix or a subword. In this way, indiscernibility relations among strings (they are equivalence or tolerance relations) are introduced, which lead to lower and upper approximations of languages. By varying the length of the perceived substring, we get sequences of approximations converging to the language. In many cases, the approximations of context-free languages are proved to be regular languages.

DOI: 10.3233/FI-1997-32204

Citation: Fundamenta Informaticae, vol. 32, no. 2, pp. 149-162, 1997

Authors: Ruiz, Carolina | Minker, Jack

Article Type: Research Article

Abstract: We study the semantics of disjunctive logic programs that simultaneously contain multiple kinds of default negations. We introduce operators notG , notW , and notSTB in the language of logic programs to represent the Generalized Closed World Assumption, the Weak Generalized Closed World Assumption, and the stable negation, respectively. The notion of stratification involving different kinds of negations is defined and the meaning of stratified programs with multiple negations is described. The class of stratified programs is extended to the class of quasi-stratified programs and the semantics of the latest class is studied.

DOI: 10.3233/FI-1997-32205

Citation: Fundamenta Informaticae, vol. 32, no. 2, pp. 163-181, 1997

Authors: Segerberg, Krister

Article Type: Research Article

Abstract: A particular modelling for belief revision is proposed that differs in important respects from AGM, the standard modelling that has dominated current discussion for more than a decade: its Grove models are not linear and it can handle iterated change.

Keywords: Belief revision, theory change, epistemic logic

DOI: 10.3233/FI-1997-32206

Citation: Fundamenta Informaticae, vol. 32, no. 2, pp. 183-191, 1997