This article is devoted to two different generalizations of projective Boolean algebras: openly generated Boolean algebras and tightly σ-filtered Boolean algebras. We show that for every uncountable regular cardinal κ there are 2 pairwise non-isomorphic openly generated Boolean algebras of size κ > א1 provided there is an almost free non-free abelian group of size κ. The openly generated Boolea...

In large process deployments where an enterprise has to model and maintain a large number of processes that are specializations of each other it is advantageous to provide formal support for process specialization called process inheritance. A process inheritance model definition is introduced as well as a process definition language construct for defining process specialization.

In a recent project the Ada language turned out to be not as flexible as we expected it to be. This forced us to model our application in a way that was less elegant, less maintainable and less efficient. In this paper we propose to add a language construct to the language that would enable us to do what we were missing. The extension is based on finite unions with dispatching and can quite eas...

A hyperbolic bration is set of q ?1 hyperbolic quadrics and two lines which together partition the points of PG(3; q). The classical example of a hyperbolic bration comes from a pencil of quadrics; however, several other families are known. In this paper we construct a new family of hyperbolic brations for odd prime powers q. As an application of hyperbolic brations, we note that they can be us...

This paper studies the information content of some Ifo indicators. In particular, we investigate whether two Ifo indicators, one on the current business situation, the other on current production development, provide information on revisions of German industrial production. A new feature of our analysis is the construction and use of a real-time dataset. We conclude that the Ifo indicators play...

It has been recognized that there is a need for a language mechanism that support reuse of collections of related classes. Existing approaches either use an enclosing class for this purpose, or introduce a special purpose, new language construct. In this paper we explore the use of packages for the grouping of related classes. Ordinary packages are already grouping of classes, so we explore the...

We introduce and study a tactic language, Hitac, for constructing hierarchical proofs, known as hiproofs. The idea of hiproofs is to superimpose a labelled hierarchical nesting on an ordinary proof tree. The labels and nesting are used to describe the organisation of the proof, typically relating to its construction process. This can be useful for understanding and navigating the proof. Tactics...

According to J.A.N. Lee in 1996, computer scientists “are reaching the stage of development where each new generation of participants is unaware both of their overall technological ancestry and the history of the development of their speciality, and have no past to build upon” [1, p.54]. A technically and historically accurate account, as attempted here, can help us, computer scientists, grasp ...

Common conceptions of the notions of role, relationship, and collaboration in object-oriented programming and related disciplines are briefly recalled and related to each other, working towards a view that allows it to fit them all together, eventually setting the cornerstones for the definition of a truly useful and widely accepted novel programming language construct.

While finite cop-win finite graphs possess a good structural characterization, none is known for infinite cop-win graphs. As evidence that such a characterization might not exist, we provide as large as possible classes of infinite graphs with finite cop number. More precisely, for each infinite cardinal and each positive integer k, we construct 2 non-isomorphic k-cop-win graphs satisfying addi...