In studying effective structures we investigate the effective content of typical notions and constructions in many branches of mathematics including universal algebra and model theory. In particular, we are interested in the possibilities of effectivizing model–theoretic or algebraic constructions and the limits on these possibilities. For instance, we try to understand whether certain results ...

The Linguistic Geometry (LG) approach to discrete systems was introduced by B. Stilman in early 80s. It employed competing/cooperating agents for modeling and controlling of discrete systems. The approach was applied to a variety of problems with huge state spaces including control of aircraft, battlefield robots, and chess. One of the key innovations of LG is the use of almost winning strategi...

A new second-order Eulerian code is compared with a version of the TREESPH code formulated by Hernquist & Katz (1989) for the standard isothermal collapse test. The results indicate that both codes produce a very similar evolution ending with the formation of a protostellar binary system. Contrary to previous first-order calculations, the binary forms by direct fragmentation, i.e., without the ...

In recent years, two different approaches for learning register automata have been developed: as part of the LearnLib tool algorithms have been implemented that are based on the Nerode congruence for register automata, whereas the Tomte tool implements algorithms that use counterexample-guided abstraction refinement to automatically construct appropriate mappers. In this paper, we compare the L...

This is the first paper on constructive concurrent dynamic logic (CCDL). For the first time, either for concurrent or sequential dynamic logic, we give a satisfactory treatment of what statements are forced to be true by partial information about the underlying computer. Dynamic logic was developed by Pratt [V. Pratt, Semantical considerations on Floyd–Hoare logic, in: 17th Annual IEEE Symp. on...

While different algebraic structures have been proposed for the treatment of concurrency, finding solutions for equations over these structures needs to be worked on further. This article is a survey of process algebra from a very narrow viewpoint, that of finite automata and regular languages. What have automata theorists learnt from process algebra about finite state concurrency? The title is...

Smullyan's notion of eeectively inseparable pairs of sets is not the best eeec-tive/constructive analog of Kleene's notion of pairs of sets inseparable by a recursive set. We present a corrected notion of eeectively inseparable pairs of sets, prove a characterization of our notion, and show that the pairs of index sets eeectively inseparable in Smullyan's sense are the same as those eeectively ...