Fundamenta Informaticae - Volume 48, issue 4

Authors: Nguyen, Ngoc Thanh

Article Type: Research Article

Abstract: A representation choice problem is based on the selection of an object (or objects), which should at best represent a given set of objects. In this paper we propose to solve this problem by using distance functions between objects. These distance functions are used to define representation choice functions. Six postulates for representation choice functions are given and their analysis is presented. The theoretical results provide us with some interesting relationships between classes of choice functions …specified by the accepted postulates. They also make it possible to specify essential properties of considered choice functions. In particular, it has been proved that in practical settings it is suggested to use functions from two particular classes, for they preserve important features. Less popular representation choice functions are also pointed at and analyzed. Show more

Keywords: distance function, representation choice problem, consensus method

Citation: Fundamenta Informaticae, vol. 48, no. 4, pp. 295-314, 2001

Authors: Puntigam, Franz | Peter, Christof

Article Type: Research Article

Abstract: Process types statically ensure the acceptability of all messages sent to an object even if the set of acceptable messages changes dynamically. As proposed so far, process types do not ensure the return of answers; deadlocks may prevent objects from behaving as expected. In this article we propose an object calculus with types distinguishing between obligatory messages (that must be sent, for example, as answer to a question) and optional messages (that can, but need not …be sent). A type checker enforces the sending of obligatory messages and ensures that obligatory messages are not suppressed by deadlocks. The proposed type concept supports subtyping. Show more

Keywords: types, subtyping, object calculus, concurrency, deadlocks

Citation: Fundamenta Informaticae, vol. 48, no. 4, pp. 315-341, 2001

Authors: Sakai, Hiroshi

Article Type: Research Article

Abstract: This paper presents a tool for handling equivalence relations in non-deterministic information systems. Some applications of equivalence relations are also shown. In a deterministic information system, it is possible to define an equivalence relation for any set of attributes. However, in a non-deterministic information system, some kinds of equivalence relations which we call possible equivalence relations are definable. This paper proposes two effective procedures producing all possible equivalence relations for any non-deterministic …information system and any set of attributes. The details of algorithms, the implementation of algorithms and applications to the rule extraction, etc. are presented. Show more

Keywords: equivalence relation, non-deterministic information, tool

Citation: Fundamenta Informaticae, vol. 48, no. 4, pp. 343-362, 2001

Authors: Stachniak, Zbigniew

Article Type: Research Article

Abstract: In this paper we propose a general-purpose first-order automated reasoning framework based on the notion of a definite formula and on a non-clausal variant of SLD-resolution. This framework provides a universal Horn clause-like representation of knowledge for classical as well as a range of non-classical first-order logics. It provides a resolution-style method for automated reasoning with theories of definite formulas.

Keywords: automated reasoning, non-clausal resolution, definite formula

Citation: Fundamenta Informaticae, vol. 48, no. 4, pp. 363-388, 2001

Authors: Tyszkiewicz, Jerzy

Article Type: Research Article

Abstract: We consider a model of querying remote databases, in which we compute results of queries not supported by the database system, by using sequences of supported queries and analysing locally their results. We study the expressiveness of this model of computation, as well as its complexity, measured in terms of the number of queries used.

Keywords:

Citation: Fundamenta Informaticae, vol. 48, no. 4, pp. 389-414, 2001