Turku Centre for Computer Science

About: Turku Centre for Computer Science is a facility organization based out in Turku, Finland. It is known for research contribution in the topics: Decidability & Word (group theory). The organization has 382 authors who have published 1027 publications receiving 19560 citations.

Asynchronous system synthesis

Abstract: We propose a method for synthesising a set of components from a high-level specification of the intended behaviour of the target system. The designer proceeds via correctness-preserving transformation steps towards an implementable architecture of components which communicate asynchronously. The interface model of each component specifies the communication protocol used. At each step a pre-defined component is extracted and the correctness of the step is proved. This ensures the compatibility of the components. We use Action Systems as our formal approach to system design. The method is inspired by hardware-oriented approaches with their component libraries, but is more general. We also explore the possibility of using tool support to administer the derivation, as well as to assist in correctness proofs. Here we rely on the tools supporting the B Method, as this method is closely related to Action Systems and has good tool support.

Optimal Lower Bound for 2-Identifying Codes in the Hexagonal Grid

Abstract: An $r$-identifying code in a graph $G = (V,E)$ is a subset $C \subseteq V$ such that for each $u \in V$ the intersection of $C$ and the ball of radius $r$ centered at $u$ is non-empty and unique. Previously, $r$-identifying codes have been studied in various grids. In particular, it has been shown that there exists a $2$-identifying code in the hexagonal grid with density $4/19$ and that there are no $2$-identifying codes with density smaller than $2/11$. Recently, the lower bound has been improved to $1/5$ by Martin and Stanton (2010). In this paper, we prove that the $2$-identifying code with density $4/19$ is optimal, i.e. that there does not exist a $2$-identifying code in the hexagonal grid with smaller density.

Playing with Subshifts

Abstract: We study the class of word-building games, where two players pick letters from a finite alphabet to construct a finite or infinite word. The outcome is determined by whether the resulting word lies in a prescribed set a win for player A or not a win for player B. We focus on symbolic dynamical games, where the target set is a subshift. We investigate the relation between the target subshift and the set of turn orders for which A has a winning strategy.

Decision problem for shuffled genes

Abstract: We consider a permutation-based model for the gene assembly process in ciliates. We give a procedure to decide whether a given micronuclear molecule may be assembled by using only simple dlad operations. We solve the problem based on a notion of dependency graph.