In this paper, we define the notions of ultra and involution ideals in $BCK$-algebras. Then we get the relation among them and other ideals as (positive) implicative, associative, commutative and prime ideals. Specially, we show that in a bounded implicative $BCK$-algebra, any involution ideal is a positive implicative ideal and in a bounded positive implicative lower $BCK$-semilattice, the not...

We argue that both Russellian and Heimian definites exist in natural languages. Our account captures both the commonality and difference between the two. Further, we suggest that the Russel-lian/Heimian distinction extends to indefinites too.

Certain set theoretical notions cannot be split into finer subnotions.

The λ-calculus is considered an useful mathematical tool in the study of programming languages, since programs can be identified with λ-terms. However, if one goes further and uses βη-conversion to prove equivalence of programs, then a gross simplification is introduced (programs are identified with total functions from values to values), that may jeopardise the applicability of theoretical res...

Persistence is a widely investigated fundamental property of concurrent systems, which was extended in many ways. We propose a unified characterisation of several notions considered in the literature. The main result of the paper is a detailed description of a general and extendable framework that allows to state decision problems for different persistence notions (well known as well as newly f...

The "middleware" of the World Wide Web consists of a bunch of CGI gateways and server modifications, still many of them research prototypes. However, there is a fast growing market for products, that allow the integration of legacy information systems into the World Wide Web. This article presents some concepts and notions in this very important context. This concepts allow the comparison of di...

We prove that the Sacks forcing collapses the continuum onto d, answering the question of Carlson and Laver. Next we prove that if a proper forcing of the size at most continuum collapses ω2 then it forces ♦ω1 . Research partially supported by KBN 654/2/91 Research partially supported by “Basic Research Foundation” administered by The Israel Academy of Sciences and Humanities. Publication 475.

Developments in the theory of individual decision-making have been partly shaped by two criteria: a desire for models consistent with experimental evidence; and a pre-commitment to models built on normatively appealing axioms. This paper explores the compatibility of these two selection criteria. The paper reconstructs and scrutinises an argument due to Friedman and Savage asserting that the no...