On commutative Kleene monoids.
On computable formal concepts in computable formal contexts.
On computable real functions
On computations with causal compositional models
The knowledge of causal relations provides a possibility to perform predictions and helps to decide about the most reasonable actions aiming at the desired objectives. Although the causal reasoning appears to be natural for the human thinking, most of the traditional statistical methods fail to address this issue. One of the well-known methodologies correctly representing the relations of cause and effect is Pearl's causality approach. The paper brings an alternative, purely algebraic methodology...
On computations with integer division
On computer aided shape optimization
On computing the distinguishing numbers of trees and forests.
On conjugacy of languages
We say that two languages and are conjugates if they satisfy the conjugacy equation for some language . We study several problems associated with this equation. For example, we characterize all sets which are conjugated a two-element biprefix set , as well as all two-element sets which are conjugates.
On Conjugacy of Languages
We say that two languages X and Y are conjugates if they satisfy the conjugacy equationXZ = ZY for some language Z. We study several problems associated with this equation. For example, we characterize all sets which are conjugated via a two-element biprefix set Z, as well as all two-element sets which are conjugates.
On connections between information systems, rough sets and algebraic logic
In this note we remark upon some relationships between the ideas of an approximation space and rough sets due to Pawlak ([9] and [10]) and algebras related to the study of algebraic logic - namely, cylindric algebras, relation algebras, and Stone algebras. The paper consists of three separate observations. The first deals with the family of approximation spaces induced by the indiscernability relation for different sets of attributes of an information system. In [3] the family of closure operators...
On context constrained squares and repetitions in a string
On context-free rewriting with a simple restriction and its computational completeness
This paper discusses context-free rewriting systems in which there exist two disjoint finite sets of rules, and a symbol, referred to as a condition of applicability, is attached to each rule in either of these two sets. In one set, a rule with a symbol attached to it is applicable if the attached symbol occurs in the current rewritten string while in the other set, such a rule is applicable if the attached symbol does not occur there. The present paper demonstrates that these rewriting systems...
On contexts of direct products, ordinal sums and ordinal products
On Continued Fractions and Finite Automata.
On continuous functions computed by finite automata
On contrast intensification operators and fuzzy equality relations.
The class of contrast intensification operators is formally defined and it's lattice structure studied. The effect of these operators in the referential classifications derived from special kinds of fuzzy relations is also determined. Results and examples are presented providing contrast intensification operators which keep quasi-uniformity structures generated by fuzzy relations while diminishing the fuzziness or the entropy of the relations.
On Convex Body Chasing.
On Core XPath with Inflationary Fixed Points
We prove the undecidability of Core XPath 1.0 (CXP) [G. Gottlob and C. Koch, in Proc. of 17th Ann. IEEE Symp. on Logic in Computer Science, LICS ’02 (Copenhagen, July 2002). IEEE CS Press (2002) 189–202.] extended with an Inflationary Fixed Point (IFP) operator. More specifically, we prove that the satisfiability problem of this language is undecidable. In fact, the fragment of CXP+IFP containing only the self and descendant axes is already undecidable.
On critical exponents in fixed points of -uniform binary morphisms
Let be an infinite fixed point of a binary -uniform morphism , and let be the critical exponent of . We give necessary and sufficient conditions for to be bounded, and an explicit formula to compute it when it is. In particular, we show that is always rational. We also sketch an extension of our method to non-uniform morphisms over general alphabets.
On Critical exponents in fixed points of k-uniform binary morphisms
Let w be an infinite fixed point of a binary k-uniform morphism f, and let Ew be the critical exponent of w. We give necessary and sufficient conditions for Ew to be bounded, and an explicit formula to compute it when it is. In particular, we show that Ew is always rational. We also sketch an extension of our method to non-uniform morphisms over general alphabets.